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Datasheet - Spec SMB463

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Document History and Modifications



Rev. N°        Chapter       Description / Changes                                                         Name Date
0.1                           First Issue                                                                  Sd        10.09.08
0.2                           - Chapter 6.10: Update Register Table                                        Sd        20.11.08
                              - Chapter 6.4.2: New partitioning of text for WR_GRANGE
                              - Chapter 2.4: Proposal for application schematic
                              - Chapter 0: Update Table of contents
                              - Chapter 5.3.5: Update resistance tolerance for digitals pins
                              - Chapter 2.5.3: Update transfer function for FIR filter
                              - Chapter 6.5: Additional description of HE failure detection
                              - Chapter 6.6.8: Wrap around counter frequency
0.3            6.12           Update of Register Table                                                     Sd        28.12.09
               6.4.2          New partitioning of text for WR_GRANGE
               2.4            Text update regarding external components
               2.5.3          Update transfer function for FIR filter
               5.3            Noise tolerances included
               5.3.5          Non-Linearity included
0.4            5.3            Update of tolerance values for sensitivity, zero-g offset, self-             Sd        27.04.09
                              test, noise
               6.5.1          Update of description for DEVSTAT1_REG = 4
               6.7            Update of timing parameters
                              Änderungsnummer 1039 R00 239                                                           21.01.10




                          AE/ESE3                          AE/ESE               AE/SCS                        RtP1/QMM

   Date                    27.04.09                       28.04.09              04.05.09                        28.05.09


Signature           Signed: Offenberg                 Signed: Finkbeiner    Signed: Westbeld                Signed: Nieder




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Single-Channel/Dual-Channel Accelerometer
          for Airbag Applications
               SMB455/465
          with open SPI Protocol

                                                      General Use




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     0. Table of contents


     1.              Introduction

     2.              Device Options
     2.1.            General Description of the Sensor Family
     2.1.1.          Schematic Drawing
     2.1.2.          Theory of Operation
     2.2.            Dual axis block diagram
     2.3.            Single axis block diagram
     2.4.            Application Hint / External Components
     2.5.            Description of Block Diagram
     2.5.1.          Δ/Σ Converter
     2.5.2.          Decimation Filter
     2.5.3.          FIR Filter (Output)
     2.5.4.          Sensitivity Calibration
     2.5.5.          Offset Cancellation
     2.5.6.          Linear interpolation
     2.5.7.          State Machine & On-Chip Oscillator
     2.5.8.          Signal delays
     2.5.9.          Arming Pin
     2.5.10.         EEPROM

     3.              Power on phase and initialization
     3.1.            Self Test

     4.              Physical Characterization
     4.1.            Size and Geometry (mechanical drawing, all dimensions in mm)
     4.2.            Output Signal Orientation
     4.2.1.          Sensing Direction Sensor
     4.2.2.          Signal orientation front crash
     4.2.3.          Signal orientation side crash
     4.3.            Marking
     4.3.1.          Marking on package
     4.3.2.          Electronic Serial No. (48bit serial number)
     4.4.            Pin-out and Pin Function

     5.              Characteristics
     5.1.            Absolute Maximum Ratings
     5.2.            Mechanical Characteristics
     5.3.            Electrical and Sensitivity Parameters Characteristics
     5.3.1.          25g range
     5.3.2.          35g range
     5.3.3.          50g range
     5.3.4.          70g range
     5.3.5.          Common parameters (for 35g, 50g and 70g ranges, 25g range tbd)

     6.              Interface Description
     6.1.            Introduction
     6.2.            Communication
     6.2.1.          General Instruction Format
     6.3.            Acceleration commands
     6.3.1.          Function of SI bits for acceleration commands
     6.3.2.          Function of SO bits for acceleration commands
     6.4.            Non acceleration commands
     6.4.1.          Range selection



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     6.4.2.          Command WR_GRANGE
     6.4.3.          Command RD_GRANGE
     6.4.4.          EOI bit in Device Control Register
     6.4.5.          Offset cancellation
     6.5.            Error Management
     6.5.1.          Error management for acceleration commands
     6.5.2.          Error management for non acceleration commands
     6.6.            SPI Instruction Set
     6.6.1.          RD_DEVICE_ID
     6.6.2.          RD_REVISION_ID
     6.6.3.          RD_DEVSTAT1_REG
     6.6.4.          RD_DEVSTAT2_REG
     6.6.5.          RD_SENSOR_DATA
     6.6.6.          WR_DEVCTL
     6.6.7.          RD_DEVCTL
     6.6.8.          RD_READCNT
     6.6.9.          Electrical serial number
     6.7.            Timing Parameters
     6.8.            Recommendations
     6.9.            Internal Counter
     6.10.           Register Table

     7.              Qualification
     7.1.            Life Expectancy
     7.2.            Solderprofile leadfree
     7.3.            Whisker test - for galvanic pure tin surface (not soldered on a PCB)
     7.4.            X-Ray Inspection
     7.5.            Washability
     7.6.            Moulding and Varnishing/Coating
     7.7.            Handling Instruction
     7.8.            Leadfree
     7.9.            Customer key parameters

     8.              Qualification Plan

     9.              Technology Information




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     1. Introduction

The SMB455/465 sensor is designed for crash sensing in automotive airbag applications. The SMB455/465
sensor is a in-plane sensor with a measurement range of  25/35/50/70g via g-range SPI command. The
sensor provides acceleration data for evaluation by a microcontroller.                 The digital SPI interface allows
bidirectional data transmission.


Sensor Type           Axis           Range                Bosch Part N°   Comment
SMB455                X               25/35/50/70g       0 273 141 030
SMB465                X/Y             25/35/50/70g       0 273 141 029



Main features of the sensors are:


    Digital output with 10bit resolution.
    Interface: SPI (16bit, 8MHz, global open SPI protocol).
    On chip 1bit /-ADC.
    Sampling rate 7.8125 kHz
    Full scale measurement range  25/35/50/70g for both channels.
    Full self test capability; triggerable positive / negative test response.
    Fast/slow on-chip offset adjustment during power-on stage/operating mode
    On-chip digital-lowpass-filter with an corner frequency of 378Hz.
    Output independent of power supply voltage (non-ratiometric output).
    0g output = 0 LSB.
    Internal error monitoring function.
    Standard SMD SOIC14n-package.
    Extended Automotive Temperature Range (-40...+105°C).
    48 bit serial number




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     2. Device Options

Component             Guaranteed                        Comment
  Name                 g Range
 SMB455                  ±25g                        Single axis sensor
 SMB455                  ±35g                        Single axis sensor
 SMB455                  ±50g                        Single axis sensor
 SMB455                  ±70g                        Single axis sensor
 SMB465              ±35g / ±35g                      Dual axis sensor
   SMB465            ±35g / ±50g                     Dual axis sensor
   SMB465            ±35g / ±70g                     Dual axis sensor
   SMB465            ±50g / ±35g                     Dual axis sensor
   SMB465            ±50g / ±50g                     Dual axis sensor
   SMB465            ±50g / ±70g                     Dual axis sensor
   SMB465            ±70g / ±35g                     Dual axis sensor
   SMB465            ±70g / ±50g                     Dual axis sensor
   SMB465            ±70g / ±70g                     Dual axis sensor
   SMB465            ±25g / ±25g                     Dual axis sensor
   SMB465            ±25g / ±35g                     Dual axis sensor
   SMB465            ±25g / ±50g                     Dual axis sensor
   SMB465            ±25g / ±70g                     Dual axis sensor
   SMB465            ±35g / ±25g                     Dual axis sensor
   SMB465            ±50g / ±25g                     Dual axis sensor
   SMB465            ±70g / ±25g                     Dual axis sensor


Note:
SMB455/465 are designed for g-ranges of 25g/35g/50g/70g. For SMB465 all range combinations are
selectable.
For SMB455 the single channel sensing element CMB457 (70g), for SMB465 the dual channel sensing
element CMB467 (70g) are used.




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2.1. General Description of the Sensor Family

2.1.1. Schematic Drawing

    X/Y Comb
    Structures                                                       8
                        14
                                                                         SOIC Plastic Housing




                                                                               ASIC




                         1                                           7




The sensors consist of a micromachined sensor chip and an evaluation ASIC both packaged into a surface
mountable standard SOIC14 narrow package.



2.1.2. Theory of Operation

Micromachined Sensor Chip

On the sensor chip, silicon surface micro-machined comb structures are used as capacitive accelerometers.
Each comb structure forms a differential capacitor, consisting of a free-movable seismic mass suspended by
silicon spring bars, and fixed counter electrodes. The seismic mass deflects due to an acceleration along the
sensing axis. This deflection results in a capacitance change which is evaluated by the ASIC.
The sensor uses micro-machined structures on the surface of the sensor chip which are protected and
hermetically sealed by a micro-machined silicon cap.

ASIC

The evaluation ASIC, transforms the capacitance change of the sensor elements into a digital bit stream by
a ΣΔ-converter. The sample rate is reduced and formed into a parallel bit word by a digital decimation filter
and filtered by a digital FIR filter for final low pass filtering.
Bi-directional data transmission with the SMB465/SMB455 using the SPI interface allows to read
acceleration data, select the sensitivity ("g-range") and control the offset adjustment and self test modes.
The device provides an on-chip, non programmable ID containing general ASIC data.




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2.2 Dual axis block diagram




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2.3 Single axis block diagram




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2.4 Application Hint / External Components


                  SGND           1                      14     SGND
                   DNC                                          DNC
                 RESET                                         VDDA
                    AP                                         AGND      C2        C3

                 DGND                                           CS
          C1      VDDD                                          SCK
                     S                                           SI
                                     7                   8



Denom.         Used for                       Parameters     Value     Tolerance
C1             Decoupling VDDD                16V            100nF     10%
C2             Decoupling VDDA                16V            100nF     10%
C3             Decoupling VDDA                16V            100nF     10%

The maximum value for a single blocking capacitor on the supply lines VDDA and VDDD is 100nF.
For FMEA reasons and for best performance it is possible to use two or more capacitors in a parallel
connection between VDDA-AGND and between VDDD-DGND (connected as short as possible).


The characterisation, qualification and product release has been done with the above described
application schematic.

When designing the PCB the following information shall be considered by the customer:
1. The positioning of the external components, i.e. the layout of the printed-circuit board, can affect
some parameters such as EMC performance or noise.
2. The capacitor values of the external components can affect some parameters such as EMC
performance or noise.
3. The customer shall ensure that the sensor signals are correctly recognised and interpreted from
the receiver ASIC and/or microcontroller in the application including external components



2.5 Description of Block Diagram


2.5.1 Δ/Σ Converter


The Δ/Σ converter converts differential capacitance change in the micromachined sensor element,
corresponding to an acceleration in the sensing axis, is converted into a digital serial bit stream by a Δ/Σ
converter at a rate of fOSC/16 (~125kHz), where fOSC is the frequency of the system clock.


2.5.2 Decimation Filter



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The decimation filter reduces the sample rate from 125 kHz to 7.8125 kHz.
It is a third-order filter with the following transfer function:



                                                                   3
                                                            -16
                                             3         1-z
                        H(z) = 1 /16 *
                                                       1 - z -1




2.5.3 FIR Filter (Output)

The complete transfer function of decimation and FIR filter compared to a 3rd order Bessel filter is shown in
the diagramm below. The -3dB corner frequency of the complete filter is 378 Hz.




For the final low pass filtering, a 14Tap symmetrical FIR filter with a data rate of 7,8125 kHz is used.
H(z) = (b0 + b1*z^-1 + b2*z^-2 + ..... + b13*z^-13) / (b0 + b1 + … + b13)

The realized coefficients converted to integer are as follows:
9, 25, 52, 87, 125, 157, 176, 176, 157, 125, 87, 52, 25, 9

To get the real value of the coefficients, they have to be multiplied with 2-10.




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2.5.4 Sensitivity Calibration

An adjustable gain amplifier stage is used for sensitivity calibration during the production process.
The gain amplifier stage is been adjusted with bits #57 - 63 for channel x and bits #66 - 72 for
channel y.




2.5.5 Offset Cancellation

The SMB465/SMB455 provides on-chip offset cancellation for each channel to enable automatic offset
cancellation for the 0g output level. The offset cancellation will eliminate any offset on the output of the
SMB465/SMB455 to 0 lsb using an increment/decrement algorithm.
The offset cancellation includes two modes:
    Fast offset cancellation is used after power-on
    Slow offset cancellation for continuously running offset cancellation in normal mode.


                                          Initial Offset
         Out
          [lsb]

                                               Out                      Final Offset

         0
                                     t



                                                                t [ms]




                                  Start offset Cancellation




Schematic representation of the offset cancellation method in the 7.8125 kHz cycle




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Principle of the offset cancellation.

  A)    For each calculation cycle the output signal is calculated by subtraction of the current accumulated
      offset value from the current input value. The offset cancellation algorithm is executed with a frequency
      of 7.8125 kHz.
  B) Offset cancellation has two operation modes: fast offset cancellation and slow offset cancellation.
  C) In fast cancellation mode an update of the accumulated offset value is performed in every internal
      execution cycle (128µsec) in the following way: If the output signal is positive, one lsb is added to the
      accumulated offset value. If the output signal is negative, one lsb is subtracted from the accumulated
      offset. If the output signal is equal to zero the accumulated offset value will not be changed.
  D) The accumulated offset value is stored in a 12 bit variable. The offset subtraction is performed in 12 bit
      precision; the output is presented in 10 bit resolution. The reduction of the data representation from 12
      bit to 10 bit is performed after offset subtraction using a rounding operation.
   E) In each offset update cycle only one update of the accumulated offset value is performed.
   F) In slow update mode, in each 7.8125 kHz update cycle, a slow offset cancellation counter is
      incremented or decremented according to the method described in C). If the slow offset cancellation
      counter reaches 1953, the accumulated offset is incremented by one lsb. If this counter reaches -1953
      lsb, the accumulated offset value is decremented by one lsb. After each decrement/increment of the
      accumulated offset, the slow offset cancellation counter is reset to zero. As described above, the
      accumulated offset is stored in a 12 bit variable.
   G) In fast update mode this can lead to an offset change by one 12 bit lsb every 128 µsec or one 10 bit
      (output digits) lsb every 512 µsec. This corresponds to a compensation speed of 1953 10bit lsb per
      second.
      In slow update mode the fastest offset change is thus one 12 bit lsb every 128 µsec * 1953 = 0.25 sec
      or one 10 bit (output digits) lsb every sec. This corresponds to a compensation speed of one
      10bit lsb per second. The compensations speeds in fast and slow offset cancellation mode may vary
      with the precision of the sensor internal clock. In effect for 10 bit resolution, this means a minimum
      offset cancellation speed of 1855 lsb /sec and a maximum offset cancellation speed of 2051 10 bit
      lsb/sec. In slow offset cancellation mode, the minimum fastest speed is 0.95 lsb /sec, the maximum
      fastest speed is 1.05 lsb /sec.
  H) The step size in physical units [g] is therefore dependent on the selected g-range.
  I) The initial value for the offset accumulator after power-on and after reset of the sensor- is nominal
      'zero'.




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  2.5.6 Linear interpolation




2.5.7 State Machine & On-Chip Oscillator


The state machine controls the overall behavior of the sensor, including the overall system timing, the
initialisation and on-chip self test, the offset regulation and data communication. The system clock signal
with a frequency fOSC = 2 MHz is generated by an on-chip oscillator. Note that the on-chip signal delay
tolerance is determined by the tolerance of the system clock.




2.5.8 Signal delays

               125kHz             125kHz                 7,8125kHz        7,8125kHz                      2MHz


                          S/D               Dec-Filter          FIR + Gain                                      Register
                                                                               Offs. Reg    Interpolation
   Sensor                                                      (832 + 9) µs                                                        SPI
                         (8 µs)              (192 µs)                           (0,5 µs)       (128 µs)
                                                                                                                Register


                                         Note: The on-chip signal delay tolerance is determined by the tolerance of the system clock




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2.5.9 Arming Pin




Default status of the Arming Pin AP after reset: Z  high impedance.
The arming pin output signal AP on Pin 4 is used additionally for the supplier specific function (EC-TEST).
The arming pin feature shall be active when the fast offset cancellation is not active.
After a request of acceleration data with or without activated selftest, the sensor data of the requested
channel are compared to internal range independent arming pin threshold values.
If the threshold values are reached, the arming pin has digital output low during the next data frame when
the sensor data of the requested channel are being transmitted.
Otherwise (also in case of error transmission) the arming pin stays at Z  high impedance.
For a dual axis sensor this function shall be independently performed both channels 1 and 2.


2.5.10 EEPROM

The SMB455/465 features a 96bit programmable array (EEPROM) organised in a 24 x 4 bit
structure.

  Address (dec)                                                   Function
  0-3                                                             band gap calibration data
  4-7                                                             oscillator trimming data (MSB)
  8 - 55                                                          48bit serial number
  56                                                              lock bit for band gap, oscillator trimming data
                                                                  and 48bit serial number
  57-63                                                           fine gain channel X
  64                                                              sensor type (SMB455=1/465=0)
  65                                                              lock bit for fine gain channel x and sensor type


  66 - 72                                                         fine gain channel Y
  73 - 76                                                         positive self test trimming channel X
  77 - 80                                                         negative self test trimming channel X
  81 - 84                                                         positive self test trimming channel Y
  85 - 88                                                         negative self test trimming channel Y
  89                                                              lock bit for fine gain channel Y and for all self
                                                                  test trimming data
  90                                                              oscillator trimming data (LSB)
  91 - 95                                                         CRC / parity check



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     3. Power on phase and initialization

      (1)                    (2)                             (3)                                   (4)                       (5)

  Power-          Waiting for g-Range Sensor ready                                    Test phase                       Normal
  up time         selection SPI                                                                                        Operation
                  command
                                      (Performs fast offset                           - configure device control
                                      cancellation)                                   register
                                                                                      - arming pin active

      t1                     t2                                    t3                              t4                        time
  Release of RESET                                                                     WR_DEVCTL                        Command EOI
                                                                                       OFFC = 1


t1 = 1ms maximum
   Power up time (time after providing supply Voltage on sensor Vs pins and Reset pin)
   Power up time (time after providing supply voltage on Reset pin after Reset. (Vs always at supply voltage)
t2 = application specific due to range selection command by ECU
t3 = minimum fast offset cancellation time > 367ms for 25g
t4 = customer specific due to commands by ECU
t5 = normal operation after setting EOI



3.1 Self Test
The SMB465/SMB455 features a bidirectional on-chip self test, controlled by SPI commands. In the self test
mode the seismic mass is deflected by an electrostatic force, generating a static self test response. The self
test response is defined in the electrical parameters. Thus, it provides full testing of the complete signal
evaluation path including the micromachined sensor structure and the evaluation circuit.

                                    positive self test
                                    amplitude
               Out                                       negative self test
              [lsb]                                      amplitude


                 0




                                                                                 t


                                                                         switch off negative self test
                                                       set negative self test amplitude

                                                      switch off positive self test

                                   set positive self test


The self test is activated by sending the self test command. The self test can be activated separately for both
directions (positive and negative direction). The self test response will remain as a static offset on the output


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until the self test is deactivated. Any acceleration applied to the sensor with the self test „switched on“ will be
seen on the output as a superposition of both acceleration and self test signal.


Software hint:
An evaluation of the self test should include the measurement of both directions and channels. The self test
response should be verified by comparison with the expected value after switching the test signal on and off.
The sensor can be directly switched from positive to negative test signal and vice versa.


Note:
The offset cancellation is stopped as long as the self test is switched on. After switching off the self test, the
offset cancellation is reactivated again also automatically (slow mode only).
The self test cannot be activated when the offset cancellation is in fast mode.




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      4. Physical Characterization

4.1 Size and Geometry (mechanical drawing, all dimensions in mm)
The sensor is packaged into an SOIC14n housing according to JEDEC standard MS-012.

4.2 Output Signal Orientation

4.2.1 Sensing Direction Sensor

                                       Ch2 (y-axis)

  1                      14            -a       +a




                                                     +a
                                                     Ch1 (x-axis)
                                                     -a

      7                    8


The sensing direction of the SMB465/SMB455 is in plane with the SOIC14 package and thus in plane with
the printed circuit board. An acceleration of the device in the "+a"-direction results in a positive output
change, a deceleration in this direction (or acceleration to the opposite side) results in a negative output
signal.
Example :
If the sensor is mounted into a car with the edge between Pins 1 and 14 in driving direction, a frontal crash
generates a negative change of the channel 1 output signal due to a negative acceleration in X axis
direction.



4.3 Marking

4.3.1 Marking on package

      o   pin 1 location marking
      o   Bosch logo
      o   product number (last five digits of Bosch part No.)
      o   date code and strip mark code
      o   assembly lot number




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  Bosch Logo                                                          Product
                                                                      Number
                                                                      (Last five digits)
                                                 NNNNN
                                              YYWW - AA
  Date Code                                 XXXXXXXXXX
                                                                       Strip Mark



  ASIC and                      1
  Sensor Wafer
  (5 + 5 Digits)


4.4 Pin-out and Pin Function

                 1                          14




                     7                        8




Pin N°        Assignment                          Description
1             SGND1                               Substrate of sensor (connect to analog GND, AGND)
2             NC                                  No internal connection (do not connect)
3             RESET                               Power-on-reset (low active)
4             AP                                  Arming pin (low active)
5             DGND                                Digital ground
6             VDDD                                Digital supply voltage
7             SO                                  SPI – master in slave out
8             SI                                  SPI – master out slave in
9             SCK                                 SPI – serial clock
10            CS                                  Chip select (low active)
11            AGND                                Analog ground
12            VDDA                                Analog supply voltage
13            NC                                  No internal connection (do not connect)
14            SGND2                               Substrate of sensor (connect to analog GND, AGND)




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       5. Characteristics

  5.1 Absolute Maximum Ratings
    Parameter                                            Min.                Nominal               Max.                     Unit.
    Supply Voltage                                       -0.3                   3.3            3.6 (4.5V)*                   Volt
    Operation Temperature
                                                          -40                                       105                      °C
    Storage Temperature                                   -55                                       150                      °C
    Shock Survival unpowered
                                                        2000                                                                     g
    (x,y,z axis)
    Drop Test to concrete floor
                                                          1.5                                                                    m
    (random)

  * 4.5V for maximum 75h 5.3 Electrical and Sensitivity Parameters Characteristics
  (TA = -40C to +105C, VS = VVDDA-AGND = VVDDD-DGND = 3.30V ± 5%, Acceleration = 0g; unless otherwise noted

  5.3 Electrical and Sensitivity Parameters Characteristics
  (TA = -40C to +105C, VS = VVDDA-AGND = VVDDD-DGND = 3.30V ± 5%, Acceleration = 0g; unless otherwise noted

  Test method Noise Peak to Peak:
  - Linear Interpolator active
  - external components according to specified circuitry proposal.
  - sampling rate 2kHz
  - SPI-frequency 2MHz

  Test method Noise RMS & zero g output:
  - Linear Interpolator active
  - external components according to specified circuitry proposal.
  - sampling rate 2kHz
  - SPI-frequency 2MHz


  5.3.1 25g range

Parameter                                             Conditions                       min          typ           max                units
Sensor
 Guaranteed full scale range                                                           ±25                                            g
Sensitivity ( non ratiometric sensor)
                                                      Frequency = 0Hz
 Sensitivity                                                                           17.29        18.2         19.11               LSB/g
                                                      Including ratiometric error

Offset ( non ratiometric sensor)
 Zero-g output                                        Including ratiometric error
                                                      Excluding Noise effects
                                                                                       -0.5                       +0.5               LSB

Self Test
                                                                                                                                     LSB
 Output change                                        Including ratiometric error      250          313            376
 Tolerance of self test response                                                        -20                        20                 %
Noise
 Output Noise RMS Value                                                                -1.7                       +1.7               LSB
 Output Noise (peak to peak)                                                            -4                         +4                LSB



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  5.3.2 35g range

Parameter                                             Conditions                    min          typ           max            units
Sensor
 Guaranteed full scale range                                                        ±35                                         g
Sensitivity ( non ratiometric sensor)
                                                                                    12.35        13.0         13.65           LSB/g
                                                      Frequency = 0Hz
 Sensitivity
                                                      Including ratiometric error
                                                                                     -5                         +5             %
Offset ( non ratiometric sensor)
 Zero-g output                                        Including ratiometric error
                                                      Excluding Noise effects
                                                                                    -0.5                       +0.5           LSB

Self Test
                                                                                                                              LSB
  Output change                                       Including ratiometric error   178          223            268
  Tolerance of self test response                                                    -20                        +20            %
Noise
 Output Noise RMS Value                                                             -1.5                       +1.5           LSB
 Output Noise (peak to peak)                                                         -3                         +3            LSB



  5.3.3 50g range

Parameter                                             Conditions                    min          typ           max            units
Sensor
 Guaranteed full scale range                                                        ±50                                         g
Sensitivity ( non ratiometric sensor)
                                                                                    8.645                      9.555          LSB/g
                                                      Frequency = 0Hz                             9.1
 Sensitivity
                                                      Including ratiometric error
                                                                                     -5                          +5            %
Offset ( non ratiometric sensor)
 Zero-g output                                        Including ratiometric error
                                                      Excluding Noise effects
                                                                                    -0.5                       +0.5           LSB

Self Test
                                                      Including ratiometric error                                             LSB
 Output change                                                                      124          156           188
 Tolerance of self test response                                                    -20                         +20            %
Noise
 Output Noise RMS Value                                                             -1.3                       +1.3           LSB
 Output Noise (peak to peak)                                                         -2                         +2            LSB




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5.3.4 70g range

Parameter                                             Conditions                      min             typ         max         units
Sensor
 Guaranteed full scale range                                                           ±70                                      g
Sensitivity ( non ratiometric sensor)
                                                                                      6.175           6.5         6.825
                                                      Frequency = 0Hz                                                         LSB/g
 Sensitivity
                                                      Including ratiometric error                                               %
                                                                                        -5                          +5
Offset ( non ratiometric sensor)
 Zero-g output                                        Including ratiometric error
                                                      Excluding Noise effects
                                                                                       -0.5                        +0.5       LSB

Self Test
                                                                                                                              LSB
  Output change                                       Including ratiometric error      89            112           135
  Tolerance of self test response                                                      -20                         +20         %
Noise
 Output Noise RMS Value                                                                -1.1                        +1.1       LSB
 Output Noise (peak to peak)                                                           -1.5                        +1.5       LSB



5.3.5 Common parameters (for 35g, 50g and 70g ranges, 25g range tbd)

Parameter                                              Conditions                     min            typ          max         units
Sensitivity
                                                                     package
 Cross-axis sensitivity                                             alignment error
                                                                                       -5                           +5         %
 Non linearity of sensitivity                                                                                       2          %
Frequency Response
                                                                    FIR 14 TAP
   -3dB frequency                                             ( ratiometric to        359           378            397         Hz
                                                           oscillator frequency )




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Parameter                                             Conditions                            min      typ max units
Oscillator Frequency                                                                        5%        2       5%     MHz
Supply current                                                     x sensor                                    8      mA
                                                                   xy sensor                                   8      mA
Offset Cancellation
                                                                 ratiometric to
 fast offset cancellation                                     oscillator frequency
                                                                                           1855     1953 2051 LSB/s
 Max. slow offset cancellation
                                                                 ratiometric to
                                                              oscillator frequency
                                                                                           0.95       1      1.05 LSB/s


Digital range                                                                                                10       bits
 Range for acceleration data                                                                -480            +480      LSB
 Logic output high (SO)                                    Max static current 2 mA         Vs-0.6            Vs       Volt
 Logic output low (SO, AP)                                 Max static current 2 mA           0.0             0.6      Volt
 Logic input high (all inputs)                                                               2.2             Vs       Volt
 Logic input low (all inputs)                                                                0.0              1       Volt
 Input capacity
                                                                                                              10       pF
 at high impedance SO
 Hysteresis for digital input pins                                                         0.25              0.60    Volt
 Internal Resistor SO                                                                       50      100      150    kOhm
 Internal Resistor SI, CS, SCK                              SI with pull up resistor        75      108      140    kOhm
 Internal Resistor Reset Pin                                  Pull down resistor            75      108      140    kOhm
 Internal Resistor AP                                                                       50      100      150    kOhm
Low voltage detection
 Power down threshold                                                                      2.65              2.86     Volt
 Power up threshold                                                                                           2.9     Volt
 Undervoltage reset time                                VDDA or VDDD below threshold        1.5               8.0     µs
Reset Pin
 Activation time (low active)                                                               100                        ns
Arming Pin activation
 Active range (Positive signal)                                                              11              480      LSB
 Inactive range (Pin remains at Z)                                                          -10               10      LSB
 Active range (Negative signal)                                                            -480              -11      LSB
 Arming pin activation time                           CS = 1.0V, AP = 0.6V, C(AP) = 70pF                      70       ns




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     6. Interface Description

6.1 Introduction

The SMB465/SMB455 provides a bi-directional 3.3V SPI interface for communication with the ECU at a 16
bit data word size. The sensor always operates in slave mode whereas the MCU provides the master
function. The interface consists of 4 ports as shown below. (The SPI communication is working from Vs =
3.6 to Power down threshold)



                                                    SCK

                                                    CS
    Microcontroller                                                          Digital
                                                    SI            SPI     Accelerometer

                                                    SO


Serial clock (SCK) : Input for master clock signal. This clock determines the speed of data transfer and all
receiving and sending is done synchronous to this clock.


Chip Select (CS) : CS activates the SPI interface. As long as CS is high, the IC does not accept the clock
signal or data and the output SO is in high impedance. Whenever CS is in a low logic state, data can be
transferred from and to the microcontroller.


Serial Input (SI) : Accelerometer data in is latched by the rising edge of SCK. See figure below.


Serial Output (SO) : Accelerometer data out is set by the falling edge of SCK. See figure below




6.2 Communication

Communication between slave and master is realised by 16 bit data word, MSB first.
A so-called off-frame protocol is used, i.e. that each transfer is completed through a sequence of 2 phases.
The answer of a given request is sent within the very next frame.
The acceleration data for x-axis, y-axis Channel will be frozen at CS down request and submitted during
response.




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                15 14 13 12 11 10                               9    8    7    6    5         4          3        2        1   0
   SCK

  /CS

  MOSI          MSB                                                                                                            LSB


  MISO          MSB                                                                                                            LSB




  SCK

  CS

  SI


                      Request
                                                                                         Response


  SO

                                 Phase 1                                       Phase 2




6.2.1 General Instruction Format

The used SPI instructions can be subdivided into two classes, acceleration and non acceleration commands.



6.3 Acceleration commands

These commands are used to request sensor data for channel X or Y. The format of these commands is
shown below.


                15 14 13 12 11 10                          9    8    7    6    5    4     3         2        1        0
  SCK

  CS

  MOSI          CH1 CH0 SEN         -        -       -      -   -    -    -    -    -     -          -       -        -


  MISO           0    CH1 CH0           P   ST1     ST0    D9   D8   D7   D6   D5   D4   D3         D2       D1       D0


Format of acceleration commands



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For acceleration commands the bit SEN is always set to ‘1’. The function of the individual bits of SI and SO
are shown in tables below respectively.



6.3.1 Function of SI bits for acceleration commands


 Name                Bit position             Description               Definition
 CH1:CH0             15:14                    Channel select            Defines sensor channel requested
 SEN                 13                       Sensor bit                Defines sensor data request (SE = 1), or non sensor
                                                                        data request (SE = 0)

 Bit      15         14          13           12 11 10 9                8   7    6   5   4         3    2     1     0

          CH1        CH0         SEN          -      -     -        -   -   -    -   -   -         -    -     -     -      Data
                                                                                                                           requested

          0          0           1            -      -     -        -   -   -    -   -   -         -    -     -     -      x-data
 SI                                                                                                                        CH1
          0          1           1            -      -     -        -   -   -    -   -   -         -    -     -     -      y-data
                                                                                                                           CH2
          1          0           1            -      -     -        -   -   -    -   -   -         -    -     -     -      Illegal
                                                                                                                           CH3
          1          1           1            -      -     -        -   -   -    -   -   -         -    -     -     -      Illegal
                                                                                                                           CH4




6.3.2 Function of SO bits for acceleration commands


Name                      Bit position Description                          Definition
CH1:CH0                   14:13                   Channel select            Identifies sensor channel source for data in D9:D0
                                                                            ( X or Y )
P                         12                      Parity                    Ensures odd parity for bits 15:0 of SO
ST1:ST0                   11:10                   Status                    Identifies contents in D9:D0
                                                                            (sensor data, self-test data, error response)
D9:D0                     9:0                     Data                      Sensor data / self-test data / error response



Bit     15          14          13       12         11         10                            9:0
         0        CH1 CH0                 P         ST1 ST0                     D9:D0 / error response                                Device
                                                                                                                                      status
         0           -           -        -         0          0                               -                                     Not used
         0           -           -        -         0          0                               -                                        **



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            0         0          0        P         0           1                       Sensor data for channel x

            0         0          1        P         0           1                      Sensor data for channel y
            0         0          0        P         1           0                   Self-test data for channel x                                Device in
So
                                                                                                                                                self-test
                                                                                                                                                mode or
                                                                                                                                                self-test
            0         0          1        P         1           0                   Self-test data for channel y                                switched
                                                                                                                                                off for t <
                                                                                                                                                   4ms
            0         0          0        P         1           1         1 0 0 0 0                 0           0        0            0       Request
                                                                                                                                              error if 1.
                                                                                                                               RE           command is
                                                                                                                                                 not
                                                                                                                                             wr_grange
            0         0          0        P         1           1         0    0    0     0    0    0        0           HE     0     0     Hardware
            0         0          1        P         1           1         0    0    0     0    0    0        0           HE     0     0       error
            0         0          1        P         1           1         0    0    0     0    0    0       CNC           0     0     0       455 - Ch2
                                                                                                                                             455/465-Ch3
            0         1          0        P         1           1         0    0    0     0    0    0       CNC           0     0     0
                                                                                                                                             455/465-Ch4
            0         1          1        P         1           1         0    0    0     0    0    0       CNC           0     0     0     (Condition not
                                                                                                                                               correct)
            0         0         0         P         1           1         0 0 0 0 0 ND                          0        0      0     0 No data
            0         0         1         P         1           1         0 0 0 0 0 ND                          0        0      0     0 available
            Z         Z         Z         Z         Z           Z         Z Z Z Z Z Z                           Z        Z      Z     Z EEPROM
                                                                                                                                          error
** Not used means that the slave does not send such a message




6.4 Non acceleration commands

These commands are used to write/read control and status registers.


                15 14 13 12 11 10 9                                 8     7        6      5    4    3       2       1    0
     SCK

  CS

     MOSI       OP1   OP0 SEN        A4     A3      A2    A1        A0    D7       D6     D5   D4   D3      D2      D1   D0


  MISO           0    OP1    OP0      P    ST1      ST0   ES1       ES0   D7       D6     D5   D4   D3      D2      D1   D0


Format of non acceleration commands




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The function of the individual bits of SI and SO are shown respectively.
Name                    Bit position              Description        Definition
OP1:OP0                 15:14                     Opcode             Defines operation read/write
SEN                     13                        Sensor bit         Defines sensor data request (SE = 1), or non sensor
                                                                     data request (SE = 0)
A4 : A0                 12:8                      Address            For read or write operation
D7 : D0                 7:0                       Data               For write operation


Bit         15          14              13        12 : 8             7:0

            OP1         OP0             SEN       A4 : A0            D7 : D0 / -                                    Request



SI          0           1               0         A4 : A0            D7 : D0                                        Write register

            1           0               0         A4 :A0             -                                              Read register




Function of SI bits for non acceleration commands
Name                          Bit position                  Description    Definition
OP1:OP0                       14:13                         Opcode         Identifies contents of Read or Write data in D9:D0
                                                                           Copied from SI if request is granted
                                                                           else Request Error RE
P                             12                            Parity         Ensures odd parity for bits 15:0 of SO
ST1:ST0                       11:10                         Status         Always ‘11’ for non acceleration commands
ES1:ES0                       9:8                           Exception      Always ‘10’ for non acceleration commands
                                                            status
D7:D0                         7:0                           Data           error response / slave status / read data /



Bit     15          14              13        12     11        10    9      8      7: 0

        0           OP1             OP0       P      ST1       ST0   ES1    ES0    D7: D0 / error / data                                Response

        0           0               0         P      1         1     1      0      0    0       0       0       0    0        RE      0 Request error
        0           0               0         P      1         1     1      0      0    0       0       0       0    SE       0       0 SPI error
SO
        0           0               1         P      1         1     1      0      Slave status                                         Write
                                                                                                                                        response
        0           1               0         P      1         1     1      0      Read data                                            Read
                                                                                                                                        response



        Z           Z               Z         Z      Z         Z     Z      Z      Z       Z        Z       Z       Z     Z       Z   Z EEPROM
                                                                                                                                        error




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Function of SO bits for non acceleration commands


Application Hint: It is recommended to evaluate requests of write accesses in the ECU. It can be ensured
that the write access was successfully executed.

6.4.1 Range selection

After release of reset, the device awaits the SPI command WR_GRANGE specifying the g-ranges of x-
(SMB455, SMB465) and y-channel (SMB465).
The g-range selection command shall be the first SPI command sent from the microcontroller after releasing
the reset. All other SPI commands at that phase are leading to an error message “request error” and are not
executed by the device.


6.4.2 Command WR_GRANGE

                                    OpCode OP1 OP0 SEN                            A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
                                      Bit   15 14 13                              12 11 10 9  8   7  6   5   4   3   2   1   0
                                     MOSI    0  1   0                             0  1  0  1  0 MY1 RY1 MY0 RY0 MX1 RX1 MX0 RX0
                                     MISO    0  0   1                             P   1 1  1  0 MY1 RY1 MY0 RY0 MX1 RX1 MX0 RX0

If WR_GRANGE command is received the device checks the correctness of range selection data
(comparison range bits to mirror range bits). If deviation is detected the command is not executed and the
device sends error message “request error”. DEVSTAT-Flag „GRANGE“ in DEVSTAT-REG1 will NOT be
set.
Upon receipt of a valid g-range selection SPI command the g-range selection bits are stored in 4 ‘range bits’
of the RAM (RX0/1, RY0/1) (see g-range selection table) and has to be copied to 4 ‘mirror range bits’ of
RAM (MX0/1, MY0/1).
Upon receipt of a valid g-range selection SPI command the sensor starts automatically initialization phase 3.
The content of the ‘range bits’ and ‘mirror range bits’ is accessible for the application via an SPI read
command.


6.4.3 Command RD_GRANGE


                                    OpCode OP1 OP0 SEN                            A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
                                      Bit   15 14 13                              12 11 10 9  8   7  6   5   4   3   2   1   0
                                     MOSI    1  0   0                             0  1  0  1  0   -  -   -   -   -   -   -   -
                                     MISO    0  1   0                             P  1  1  1  0 MY1 RY1 MY0 RY0 MX1 RX1 MX0 RX0


During normal operation the content of the ‘range bits’ is continuously (at rate 2MHz) compared against the
‘mirror range bits’. Any deviation sets the hardware error (HE). DEVSTAT-Flag „GRANGE“ in DEVSTAT-
REG1 will be set.

                                                           MY1 RY1 MY0 RY0 MX1 RX1 MX0 RX0
    Selection of g-range




                                                  70g       X   X   X   X   0   0   0   0
                                   Channel x




                                                  50g       X   X   X   X   0   0   1   1
                                                  35g       X   X   X   X   1   1   0   0
                                                  25g       X   X   X   X   1   1   1   1
                           Channel




                                                  70g       0   0   0   0   X   X   X   X
                                                  50g       0   0   1   1   X   X   X   X
                              y




                                                  35g       1   1   0   0   X   X   X   X



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               25g     1      1      1      1                     X     X        X         X
g-range selection table (X can be either 0 or 1)


6.4.4 EOI bit in Device Control Register

EOI is bit Nr. 5 in device control register.
Default value after reset: 0
The EOI bit is used for finishing initialization phase 4 and setting the sensor in normal mode

The EOI bit shall be set by the customer after a minimum fast offset cancellation time. If this minimum fast
offset cancellation time is neglected by setting EOI bit to early, remaining raw offset will occur in normal
sensor mode.
The EOI bit can only be reset to 0 by giving a low signal to the RESET pin or by under voltage reset.
If the master (microcontroller) requests EOI = 1 by using command WR_DEVCTL, bits 4:0 in this command
will be ignored and the following actions will be performed on device control register:

               o   EOI bit is set to 1 (EOI = 1) and can not be reset to 0 again using WR_DEVCTL
               o   in case of active self test : self test is permanently switched off (ST2:ST0 = 000) and offset
                   cancellation is switched on and set into slow mode
               o   If no self test active and offset cancellation in fast mode: offset cancellation is set into slow
                   mode (OFFC = 1) and self test is permanently disabled (ST2:ST0 = 000)
               o   If no self test active and offset cancellation in slow mode: offset cancellation stays in slow mode
                   (OFFC = 1) and self test is permanently disabled (ST2:ST0 = 000)
               o   linear interpolation: bit LIN holds its value and cannot be changed anymore

     If bit EOI in device control register is set to 1, further WR_DEVCTL commands are not executed and
     request error (RE) is sent.

         Bit       15     14      13      12      11    10    9    8    7    6       5         4       3         2         1       0
         SI        0       1       0       0       1     1    1    0    0    0       EOI       LIN   OFFC       ST2       ST1      ST0

      SO           0       0       1       P       1     1    1    0    0    0       EOI       LIN   OFFC       ST2       ST1      ST0




6.4.5 Offset cancellation

Offset cancellation starts automatically after g-range selection and runs continuously. Bit OFFC in device
control register controls the mode of the offset cancellation as following:

OFFC = 0: fast mode activated/retriggered
OFFC = 1: slow mode activated

After reset default value OFFC = 0
The sensor can be switched between fast and slow offset cancellation mode without limitations when (EOI=0
and ST=0).


Relation between offset cancellation and self test for EOI = 0

              It is not possible to enable self test in fast offset cancellation mode.

              If the master (microcontroller) requests enabling self test and setting offset cancellation in fast mode
               simultaneously by using command WR_DEVCTL the sensor will send request error (RE) and the
               command will not be executed.




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         If the master (microcontroller) requests enabling self test and setting offset cancellation in slow
          mode simultaneously by using command WR_DEVCTL the self test will be triggered and the offset
          cancellation will be set into slow mode and switched off temporarily during selftest.

         If the master (microcontroller) requests switching off the self test after a self test phase using
          command WR_DEVCTL the self test will be disabled. The OFFC bit in WR_DEVCTL command will
          be ignored and the offset cancellation will be switched on in slow mode. After disabling the self-test
          the sensor needs 4 ms to return to resting state.




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6.5 Error Management
The device replays with an error response if one of the following errors has occurred:
 EEPROM error EE,
 Hardware error HE,
 SPI error SE, Request error RE
 Condition not correct error CNC
 No data available error ND
 Table below shows the setting conditions of EE, HE, SE, RE, CNC, and ND


        Flag                                                   Setting condition

         EE            This flag is set for both acceleration and non acceleration commands.
                       It is sent if the content of the EEPROM has an error. This error is detected by cyclic
                       redundancy check (CRC). The EEPROM contains calibration data for the band gap,
                       oscillator frequency, fine gain for channel x and y, testsignal trimming, sensor type
                       selection and CRC

                       This flag is also set if connection AGND is interrupted (AGND pin lifted): SO will go
                       to high impedance
                       This flag is set for both acceleration and non acceleration commands.
         RE            It is set to ‘1’ if:
                            - the applied command codes are not used
                            - write/read test register commands (extended mode commands) have been
                              received in normal mode.
                            - the 1st command after reset is not WR_GRANGE
                            - Attempt to send WR_GRANGE more than 1 time
                            - the GRANGE bits and their correspondent mirror bits don’t match (coincide)
                            - If the EOI-bit in the device control register is set to 1 and the command
                              WR_DEVCTL is sent by the master. In this case WR_DEVCTL will not be
                              executed and RE is set to “1”.
                            - If the master (microcontroller) requests self test and sets the offset cancellation
                              in fast mode simultaneously by using the command WR_DEVCTL, the sensor
                              will send request error (RE) and the command will not be executed.
                       This flag is set in the 1st message after reset (no request).
                       Non acceleration commands are allowed during fast offset cancellation.
                       This flag is set for both acceleration and non acceleration commands. It is set to
         SE            ‘1’ for request (SI) frame violation (incorrect number of SCK pulses more or less
                       than 16 pulses). The Message includes SE has always the format of non
                       acceleration commands
                       This flag is set only for acceleration commands
         HE            It is set to ‘1’ if a hardware error has occurred; see table 7 and 8 for details.
                       If HE occurred, the sensor data cannot be read anymore. Also, a HE for one
                       channel X makes it impossible to read the data of the other channel.
                       This flag is set only for acceleration commands. It is set to ‘1’ if:
        CNC                 - sensor data for channel no. 3 or 4 has been requested (CH1 = 1, CH0 = 0 or
                              CH1 = 1, CH0 = 1) for SMB465 / SMB455 or
                            - channel no. 2 (channel y) for SMB455 (single channel)
         ND            This flag is set only for acceleration commands. It is set to ‘1’ if sensor
                       data for channel x or y has been requested during fast offset cancellation is
                       active.



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6.5.1 Error management for acceleration commands


During an acceleration command different errors EE, SE, RE, HE, ND and CNC can be detected.
The EEPROM error (EE) has the highest priority, hardware error (HE) has the lowest priority.
If an SPI error occurs during an acceleration command the device sends a non acceleration error response
including SE set to ‘1’.
Table below shows the device response for all possible combinations of EE, SE, RE, HE, ND and CNC.


If the slave sends HE, the microcontroller can request the device status registers. This registers gives
information about the reason of setting the HE flag. HE is set to ‘1’ if one or more of the bits in this device
status registers is set to ‘1’.


                 HE             ND             CNC             RE         SE         EE              Device response
               detected       detected       detected        detected   detected   detected
                  -               0               0             0          0          0       Normal response (sensor data)
                  -               -               -             -          -          1                EE response
                  -               -               -             -          1          0                SE response
                  -               -               -             1          0          0                RE response
                  -               -               1             0          0          0               CNC response
                  -               1               0             0          0          0               ND response
                  1               0               0             0          0          0                HE response



                      0: error not detected
                      1: error detected




register                  Bit         Name               Description

                                                         Set to ‘1’ if the offset cancellation of channel x out of range
                                                         (capture range  683 LSB (25g),  488 LSB (35g),  341 LSB (50g),
                          0           OC1                 244 LSB (70g) , maximum possible offset before cancellation).
                                                         Reversibility: HE will be cancelled and OC1 will be reset if the offset
                                                         returns within the capture range limits.
                                                         Set to ‘1’ if the offset cancellation of channel y out of range
                                                         (capture range  683 LSB (25g),  488 LSB (35g),  341 LSB (50g),
                          1           OC2                 244 LSB (70g) , maximum possible offset before cancellation).
                                                         Reversibility: HE will be cancelled and OC2 will be reset if the offset
DEVSTAT1_REG




                                                         returns within the capture range limits.
                          2           OCC1               Set to ‘1’ if the offset cancellation for channel x is in wrong mode
                                                         (fast instead of slow)
                          3           OCC2               Set to ‘1’ if the offset cancellation for channel y is in wrong mode
                                                         (fast instead of slow)




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                  4           No internal n/a
                              clock              No register update, SPI information will not change.
                                                 Change from non acceleration data to acceleration data and vice
                                                 versa is not possible. Change from x-axis data to y-axis data and
                                                 vice versa is not possible.
                                                 Error will not be written in DEVSTAT1_REG
                  5                              Set to ‘1’ if the device is in extended mode. In this mode some
                                                 read/write commands are defined for production relevant tests.
                              Extended           These commands are allowed only in this mode. If one of these
                              mode               commands has been received in normal mode (not in extended
                                                 mode) the flag RE will be set to ‘1’. The device can be set into
                                                 extended mode through a write register command
                  6           SPIEC              Set to ‘1’ if the multiplexer of sensor data has an error (selecting
                                                 channel x instead of channel y)
                  7           GRANGE             Set to ‘1’ if g-range failure occurs




register          Bit         Name               Description
                  0                n.a.                                             n.a

                  1              DGND            The connection of the digital (DGND) ground pads is monitored and
                                                 checked against interruption.
                                                 If the DGND loose connection to the ground
                                                 potential, the “DGND” failure flags in the Device Status Register 2
                                                 will be and made available over SPI
                  2

                  3

                  4
DEVSTAT2_REG




                  5

                  6

                  7




If the connection AGND is interrupted ( “AGND pin lifted” ) the same effect as for EEPROM Error (EE) takes
place: the SO pin will go high impedant.

When the failure modes in device status register are no longer effective the dedicated failure bits are reset
immediately. This will lead to reset the flag HE immediately.


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6.5.2 Error management for non acceleration commands


During a non acceleration commands EE, SE, RE can be detected.
EE has the highest priority, and RE the lowest one. The table below shows the device response for all
possible combinations of EE, SE and RE.


RE                  SE                    EE               Device response
detected            detected              detected
0                   0                     0                Normal response
-                   -                     1                EE response
-                   1                     0                SE response
1                   0                     0                RE response



6.6 SPI Instruction Set

6.6.1 RD_DEVICE_ID

The Device ID is defined unique to allow identification of different IC-typed by software.


    Bit   15        14       13       12       11     10     9    8      7    6    5        4       3       2       1          0
    SI        1     0        0        1        0      0      0    1      -    -    -        -       -       -       -          -
    SO    0         1        0        P        1      1      1    0      DEVICE-ID for SMB455 + 465


                  Device ID SMB465: 44 hex, 01000100 bin
                  Device ID SMB455: 42 hex, 01000010 bin




6.6.2 RD_REVISION_ID

The Device Revision number may be utilised to distinguish different revisions of the SMB465/SMB455. The
contents is divided into an upper 4 bit field (SWR) reserved to define revisions corresponding to specific
software releases and a lower 4 bit field (MSR) utilised to identify the actual mask set. Both (SWR and MSR)
will start with 0000b and are increased by 1 every time a modification affecting the respective field was
made.




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  Bit     15        14       13       12        11        10      9     8     7     6     5        4       3       2       1          0
  SI          1     0        0        1         0         0       1     0     -     -     -        -       -       -       -          -
  SO      0         1        0        P         1         1       1     0     SWR                          MSR




6.6.3 RD_DEVSTAT1_REG

This command is used to read the device status register 1.


  Bit     15        14       13       12        11        10      9     8     7     6     5        4       3       2       1          0
  SI          1     0        0        1         0         0       0     0     -     -     -        -       -       -       -          -
  SO      0         1        0        P         1         1       1     0     Device status register 1



6.6.4 RD_DEVSTAT2_REG

This command is used to read the device status register 2.


  Bit     15        14       13       12        11        10      9     8     7     6     5        4       3       2       1          0
  SI          1     0        0        1         0         1       0     0     -     -     -        -       -       -       -          -
  SO      0         1        0        P         1         1       1     0     Device status register 2



6.6.5 RD_SENSOR_DATA

Read 10 bits data from channel X or Y, for details see chapter 6.3.2


  Bit     15        14           13        12        11       10 9      8     7     6     5        4       3       2       1          0
  SI          0     cadr         1          -        -        -   -     -     -     -     -        -       -       -       -          -
  SO      0         0            cadr      P         0        1   Sensor data from sensor

or
  SO      0         0            cadr      P         1        0   Sensor selftest data


Cadr (channel address): used to address the selected channel
                                      0 : channel X
                                      1 : channel Y
Acceleration data is processed and transmitted as a signed 10 bits word (2’s complement). Zero g level is
000hex. The maximum acceleration word is +480 the minimum is – 480 LSB. If the result of the internal A/D
conversion is exceeding this range, the value is clipped to the limits. So the biggest (positive) acceleration
value corresponds to 1E0hex, the biggest (negative) deceleration value corresponds to 220hex:


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            Dec                     Hex                    Acceleration Data
            +511                    1FF                    Not used
            :                       :                      :
            :                       :                      :
            +481                    1E1                    Not used
            +480                    1E0                    Maximum positive value of acceleration
            :                       :
            +1                      001
            0                       000                    0g value
            -1                      3FF
            :                       :
            -480                    220                    Maximum negative value of acceleration
            -481                    21F                    Not used
            :                       :                      :
            :                       :                      :
            -512                    200                    Not used



If the device is set in self-test mode then, the slave sends self-test data instead of sensor data. If a hardware
or SPI error has occurred, the slave sends an error response as described in error management.



6.6.6 WR_DEVCTL

This instruction can be used to execute one or more of the following actions:


 1. Change offset compensation mode of both sensor channels
 2. Trigger the internal self-test function of the sensor
 3.     Switch off / on the linear interpolation


This command is allowed only after the initialization phase. If this command is received in the initialization
phase the slave responses with request error RE.


      Bit      15       14      13      12      11     10     9       8   7       6       5    4      3            2        1         0
      SI       0        1       0       0       1      1      1       0       0       0   EOI LIN OFFC             ST2 ST1 ST0
      SO       0        0       1       P       1      1      1       0       0       0   EOI LIN OFFC             ST2 ST1 ST0




ST2:ST1:ST0                 x x 0 Self-test disabled for both channels
                            0 0 1 Positive deflection for both channels
                            0 1 1 Negative deflection for both channels
                            1 0 1 Positive deflection for x-channel and negative deflection for y-channel
                            1 1 1 Negative deflection for x-channel and positive deflection for y-channel




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Switching off selftest is delayed 4ms in device control register.


LIN:              0: switch off linear interpolation of both channels
                  1: switch on linear interpolation of both channels


Default setting: linear interpolation switched on


If switched off, the sampling rate per channel is 7.8125 kHz, this is the base mode. If switched on, linear
interpolation on both channels is activated. The interpolation does a linear interpolation between every two
measurement samples (a new sample every 128µs at 7.8125 kHz). Increasing the update frequency of the
SPI output register to 2 MHz gives a new calculated sample every 0.5µs. The total signal run time will
increase 128µs compared to the signal conditioning without linear interpolation.


Action on device control register by command WR_DEVCTL


    Request from                                              Action on device control register
 microcontroller using
    WR_DEVCTL
 EOI     OFF       ST0
           C
  0        0        0                              Default after reset, fast offset cancellation active
  0        0        1                   Selftest in fast offset cancellation mode, not executed, Request error
  0        1        0                                          Slow offset cancellation active
  0        1        1                    Selftest triggered, Slow offset cancellation disabled during selftest
  1        0        0                Fast offset cancellation changed in slow offset cancellation OFFC = 1, ST0
                                                        = 0 accepted, Freeze DEVCTL register
   1              0         1         Fast offset cancellation changed in slow offset cancellation OFFC = 1; no
                                                  selftest triggered ST0 = 0, Freeze DEVCTL register
   1              1         0                OFFC = 1 and ST0 = 0 accepted, Freeze DEVCTL register
   1              1         1        OFFC = 1 accepted, no selftest triggered ST0 = 0, Freeze DEVCTL register


6.6.7 RD_DEVCTL

Instruction to read the device control register.
  Bit     15          14    13       12      11      10   9    8     7       6       5   4       3          2       1       0
  SI          1       0     0        0       1       1    1    0         0       0   -   -       -          -       -       -
  SO      0           1     0        P       1       1    1    0      0          0   EOI LIN     OFFC ST2           ST1 ST0




6.6.8 RD_READCNT

Instruction to read the device CLK counter register. The SMB465/SMB455 features an 8 bit internal counter
register (wrap around) which is increased every 256 cycles of the internal system clock (wrap around
counter frequency of 7.8125 kHz).



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     Bit        15         14       13       12        11        10        9       8       7        6            5            4            3            2             1           0
     SI         1          0         0        1        0         0         1       1       -            -            -            -            -            -             -           -
    SO          0          1         0        P        1         1         1       0       D7       D6           D5           D4               D3       D2            D1          D0

D0-D7: Device CLK count register


6.6.9 Electrical serial number

This command is used to read the 48bit serial number.

RD_SN0
     Bit              15        14       13       12        11        10       9       8        7       6            5            4            3        2              1          0
           SI          1        0        0        0         0         0        0       0        -           -            -             -            -           -             -           -

           SO          0        1        0        P         1         1        1       0       D7           D6           D5           D4           D3       D2            D1          D0

RD_SN1
     Bit              15        14       13       12        11        10       9       8        7       6            5            4            3        2              1              0
           SI          1        0        0        0         0         0        0       1        -           -            -             -            -           -             -           -

           SO          0        1        0        P         1         1        1       0    D15 D14 D13                               D12       D11         D10           D9          D8

RD_SN2
     Bit              15        14       13       12        11        10       9       8        7       6            5            4            3        2              1          0
           SI          1        0        0        0         0         0        1       0        -           -            -             -            -           -             -           -

           SO          0        1        0        P         1         1        1       0    D23 D22 D21                               D20       D19         D18           D17         D16

RD_SN3
     Bit              15        14       13       12        11        10       9       8        7       6            5            4            3        2              1          0
           SI          1        0        0        0         0         0        1       1        -           -            -             -            -           -             -           -

           SO          0        1        0        P         1         1        1       0    D31 D30 D29                               D28       D27         D26           D25         D24

RD_SN4
     Bit              15        14       13       12        11        10       9       8        7       6            5            4            3        2              1          0
           SI          1        0        0        0         0         1        0       0        -           -            -             -            -           -             -           -

           SO          0        1        0        P         1         1        1       0    D39 D38 D37                               D36       D35         D34           D33         D32

RD_SN5
     Bit              15        14       13       12        11        10       9       8        7       6            5            4            3        2              1          0
           SI          1        0        0        0         0         1        0       1        -           -            -             -            -           -             -           -

           SO          0        1        0        P         1         1        1       0    D47 D46 D45                               D44       D43         D42           D41         D40




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6.7 Timing Parameters




Timing Reference: 0.2 Vs – 0.8 Vs (Vs = VVDDD-DGND)

Num             Parameter                                      Symbol    Min.             Max.                 Unit
-               SPI Operating frequency                        fOP       -                8.08                 MHz

A               Clock (SCK) high time                          tWSCKlh   49               -                    ns

B               Clock (SCK) low time                           tWSCKl    49               -                    ns

C               SCK period                                     tSCK      123.7            -                    ns

D               Clock (SCK) fall time                          tf        5.5              25                   ns

E               Clock (SCK) rise time                          tr        5.5              25                   ns

F               Data input (MOSI) setup time                   tsu       37               -                    ns

G               Data input (MOSI) hold time                    thi       49               -                    ns

H               Data output (SO) access time                   ta        -                43                   ns

I               Data output (SO) valid after SCK               tV        -                35                   ns

J               Data output (SO) lag time                      tlag      0                -                    ns



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K               Data output (MISO) disable time                tdis      -                100                  ns

L               Enable (SS) lead time                          tlead     62               -                    ns

M               Enable (SS) lag time                           tlag      62               -                    ns

N               Sequential transfer delay                      ttd       2.1              -                    µs
O               Internal write cycle time                      --                         2.1                  us
P               Clock enable time (Tele)                       TCLE      50               -                    ns
Q               Clock delay time (Teld)                         TCLD     50               -                    ns




6.8 Recommendations

It is recommended to test following errors during power up of the ECU:


     - RE: The response while sending the first command after release of reset must be RE
     - CNC: condition not correct via requesting sensor data of Illegal channel (see Chapter 6.3)
     - ND: no data available via requesting sensor data during initialisation phase


It is recommended to test following commands during power up of the ECU:


     - RD-DEVICE_ID: Read Device ID via checking the response (see chapter 6.6.1)
     - RD_REVISION_ID: Read Revision ID via checking the response (see chapter 6.6.2)
     - RD_DEVSTAT1_REG: Read Device Status Register via checking the response (see chapter 6.6.3)
     - RD_SENSOR_DATA: Read Sensor Data via checking the response (see chapter 6.6.4); checking
          plausibility of transmitted sensor data. (e.g Selftest and offset value in initialization phase)
     - RD / WR_DEVCTL: Read/Write Device Control Register via checking the response including right
          status of linear interpolation (see chapter 6.6.5 and 6.6.6)


It is recommended to evaluate all possible error responses (acceleration and non acceleration commands)
all the time. After getting error responses the ECU has to start defined operations, like turn on a warning
lamp (depending on ECU-system).


6.9 Internal Counter
The SMB465/SMB455 provides an on chip count register. This counter register can be read out via specific
SPI command (see chapter 6.6.7 RD_READCNT ). The value is frozen by the slope of the CS signal. The
counter is an internal wrap around counter which is increased every 256 cycles if the internal system clock
(2MHz; +/-5%). The overflow is reached after 255 increments.
By reading the register two times with a well defined delay the second counter value can be calculated and
compared with the second register value. The difference between this values multiplied with the 128µs
(1/(2MHz/255)) gives the deviation of the internal clock frequency. This feature can be used in order to
control the internal clock frequency.



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6.10 Register Table




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7. Qualification

7.1 Life Expectancy

The product is designed for a life expectancy of 15 years and a maximum of 15000 hours of operation, and
its application is limited to environmental conditions as covered by AEC-Q100. The commercial warranty and
liability is governed separately by the delivery conditions.

The aforesaid information on lifetime for which the product has been construed shall in no case be a
guarantee regarding the condition or quality of the product


7.2 Solderprofile leadfree




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7.3 Handling Instruction
Micro-mechanical sensors are designed to sense acceleration with high accuracy even at lower amplitudes
and contain highly sensitive structures inside the sensor element. The micro-machined sensors can tolerate
mechanical shocks up to several thousand "g"s. However, these limits might be exceeded in conditions with
extreme shock loads such as e.g. hammer blow on or next to the sensor, dropping of the sensor onto hard
surfaces etc.
We recommend to avoid g-forces beyond 2000g during transport, handling and mounting of the sensors in a
defined and qualified installation process.

7.4 Leadfree
The SMB455/465 is a lead-free component according to RoHS “Restriction of the use of certain hazardous
substances” (DIRECTIVE 2002/95/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL
of 27 January 2003 on the restriction of the use of certain hazardous substances in electrical and electronic
equipment).


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