A 1.4 GHz2.7V Programmable Divider for DRRS Standard in by csd59447

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									         A 1.4 GHz/2.7V Programmable Divider for DRRS
                               µ
                Standard in 0.6µm CMOS process
                            Hossein Zarei, Omid Shoaei and S. M. Fakhraie
                       Electrical and Computer Depatrment of Tehran University

                                  Email : h-zarei@khorshid.ece.ut.ac.ir

                  Abstract                              [3,4]. In this paper, a gating method for
                                                        programmability is used. With improved
A 1.4 GHz programmable divider, whose                   timing of the divider, the divider can operate
modulus can be varied from 16 to 31 is                  in the 1.4 GHz frequency band with low power
presented with improved timing of multi-                consumption. Fig.1 shows the principle of its
modulus divider structure and high-speed low-           operation. The division value includes all the
voltage embedded logic D-Flip Flop.                     integers between 2k and 2k+1 -1, where k is the
Programmability is achieved by gating the               number of the output bits of the sigma-delta
feedback signal of the first latch of the divide-       modulator. Four control bits are used to
by-2 blocks. For high-speed operation, the first        swallow cycles at progressively lower
control stage, is implemented with a simple             frequencies. The qualifying logic embedded
pseudo-NMOS logic gate. The programmable                within each divide-by-2/3 block is used to limit
divider has been simulated in a 0.6µm digital           each stage to skip over one cycle per period of
CMOS technology with 13mW power                         the output signal (OUT4). Therefore in this
consumption at 2.7V power supply             and        structure, the division value is equal to 32+D0
1.4GHz maximum frequency.                               .20+D1.21 +D2 .22 +D3 .23 +D4.24 .

             I. Introduction                             CK
                                                               High Speed
                                                                   2/3
                                                                            OUT0
                                                                                        2/3
                                                                                               OUT1
                                                                                                           2/3
                                                                                                                  OUT2
                                                                                                                              2/3      OUT3



                                                                    D0*             D1*                D2*               D3*

Digital Radio Relay Systems (DRRS) [1], is a                   High Speed
                                                                 Control
                                                                                   Control
                                                                                   Quailfier
                                                                                                      Control
                                                                                                      Quailfier
                                                                                                                         Control
                                                                                                                         Quailfier
wireless data networking standard that operates                 Quailfier
                                                                    0
                                                                                     1                  2                  3

in 1.4 GHz frequency band. Depending on the                                        D1                 D2                 D3

application, the standard channel spacing may                  D0


be varied from 25 KHz to 3.5 MHz, with three
equipment classes, GMSK, 4-QAM or 16-                          Fig. 1. A 16 modulus divider architecture.
QAM. For a sigma-delta fractional-N
frequency synthesizer, designed with this               The divide-by-2/3 blocks can be implemented
standard, a 16-multi-modulus divider was                by augmenting a divide-by-2 circuit with
needed. In the following section, we discuss            gating logic. Fig. 2 demonstrates an example of
improved gating method, so that the divider             the gating approach. The setting of D0* leads
coulde operate at required frequency with low-          to the swallowing of a pulse from the output
power dissipation. In Section III, the detail of        signal. Fig. 3 illustrates the timing diagram of a
circuit design is described. Simulation result is       multi-modulus divider with three divide-by-2/3
given in Section IV.                                    stages, where the division value is equal to “9”.
                                                        As illustrated, each control bits of the divide-
             II. Architecture                           by-2/3 block becomes asserted, only when the
                                                        input bit is set and the outputs of this block and
Conventionally, a programmable divider is               the next blocks are all zero. Referring to Fig. 2
implemented using an extension of the dual-             and Fig. 3, the following equation should be
modulus divider in which the overall divide-            satisfied.
by-2 sections are replaced with divide-by-2/3
blocks [2]. In the presented design, the                             Tqf + Td + TFF < TCK                                            (1)
programmability is achieved by the phase
switching technique in which a multipelxer              where Tqf is the delay of the first qualifying
selects the appropriate phase of the D-Flip             control circuit, Td is the delay of an AND gate
Flop. For glitch free operation, several                and TFF is the time window in which D0* is
techniques have been reported, however, with            “high”.
these techniqus, the chip area of the divider
and its power dissipation would be increased
                     QA_0                           QB_0
                                                                    maximum speed of the divider is increased so
             D   Q                                          OUT_0
                                            D   Q
                                                                    that this structure can operate up to 1.4 GHz in
                 Q
                                                Q
  CK                                                                a 0.6µm CMOS process with 2.7V supply
                                                                    voltage.
                      D0*
                            first control
                                circuit
                                                    OUT_1
                                                    OUT_2                      III. Circuit Design
                     D0                             OUT_3




 Fig.2. The first stage of the divider using gating method          Realization of a high-speed frequency divider
                                                                    in mixed environments, requires careful
Therefore, the maximum operating frequency                          attention to certain aspects of the circuit design
of this structure is less than the simple divide-                   to contribute low-noise to sensitive analog
by-2 (or a T-Flip Flop), since the gating and                       circuit. Therefore, source coupled logic (SCL)
control circuits increase the propagation delay                     was used to implement the divider, where
from the output of the second D-Flip Flop (D-                       differential signals at both input and output
FF) to the input of the first D-FF.                                 reduce the coupling noise from supply and
                                                                    substrate lines. In the first stage, in order to
 Clk                                                                reduce the delay time of the logic (AND, OR
Out0                                                                gates), the logic is embedded within each
                                                                    succeeding flip-flops.
Out1
                                                                    For the first stage, a high-speed divide-by-2/3
Out2                                                                and control circuit is needed. The D-Flip Flop
D0 *                                                                proposed in [5], is used for the first stage
                                                                    divide-by-2/3. Since, an inverted output of this
           Fig.3. Conventional timing diagram                       D-FF does not exist, the first control circuit is
                                                                    designed with single-ended input and output.
Clk
                                                                    Fig. 5 shows a Pseudo-NMOS logic gate used
Out0                                                                for high-speed control circuit of the first stage.
Out1                                                                Also, a new embedded AND gate is used in the
                                                                    D-FF of the first stage.
Out2
D0 *                                                                                                        D0
             Fig.4. Improved timing diagram.
                                                                                                                         D0 *
For this reason, the designers have not
                                                                    Out0        Out1         Out2         Out3
previously used this technique for high-speed
programmable dividers [3]. However, for the
required frequency (at 1.4 GHz), we chose this
                                                                           Fig. 5. The first control qualifier circuit
structure with improved timing and the low-
delay circuits for logic and qualifying control
                                                                    Fig. 6 shows this new D-FF with single-ended
blocks. The advantage of this method is the
                                                                    input and output of the first control circuit.
simple and low-power qualifying control
                                                                    When D0* is “low”, the P1, that is a relatively
circuit, which leads to lower power
                                                                    large PMOS transistor, becomes “on” and the
consumption for the divider, compared to the
                                                                    drain voltage of P1 equal to Vdd, so that the
phase switching technique. The flip-flop
                                                                    output of the first latch (QA_0) becomes “low”.
proposed in [5,6], is a low-voltage high-speed
                                                                    Therefore, the input frequency is divided by
flip-flop, however, since the 25% duty cycle of
                                                                    “2”. When D0* is asserted, P1 becomes “off”
the output signals of this D-flip flop is
                                                                    and the division ratio of this block would be
undesirable, this topology has not been used,
                                                                    equal to “3”. Other control circuits are
for the phase switching technique.
                                                                    implemented with static logic gates for low
However, if this topology is used for the first
                                                                    power consumption and with differentially
stage divide-by-2/3 of the programmable
                                                                    inputs and outputs. Also the Pseudo-NMOS D-
divider, the constraint (1) is relaxed. Fig. 4
                                                                    FF in [4] enables high-speed operation while
illustrates the improved timing, where only the
                                                                    producing a large output swing. An embedded
first stage divide-by-2/3 is designed with this
                                                                    logic D-FF designed with this proposed
flip flop with 25% duty cycle of the output
                                                                    topology, is used for other divide-by-2/3
signal. Then the time window in which D0* is
                                                                    blocks (Fig. 7). Static CMOS inverters are
“high”, is increased to 3TCK /2. Also the TFF of
                                                                    used for interstage buffering in the divider
of this flip-flop is very small. Therefore, the
                                                                    path.
                                                                        Power    Process    Operation   Power
        IV. Simulation Results                                          supply              frequency   consumption
                                                     Perrott      [3]   3V       0.6µm      900 MHz     22 mW
The programmable divider was simulated in a          Craninkx    [7]    3V       0.7µm      1.75 GHz    24 mW
                                                     Krishnapura [4]    2V       0.25µm     5.5 GHz     60 mW
0.6µm technology with HSPICE simulator. The          This work          3V       0.6µm      1.4 GHz     13 mW
sizing of the divider, especially for the first                         2V                  900 MHz     4.6 mW
stage is very critical for high-speed low-power
                                                                 Tabel. 1. Recent divider designs
operation. Therefore, the maximum operating
frequency and the power consumption, at 2.7V
power supply, were observed to 1.4 GHz and
                                                                        References
13 mW, respectively. Also at 2V power supply
                                                    [1] “Low capacity point to point Digital Radio
voltage, the maximum frequency will be equal
                                                    Relay Systems (DRRS) operating in the 1.4
to 0.95 GHz with 4.6mW power dissipation.
                                                    GHz frequency band”, ETS 300 630, March
Fig. 8 shows the maximum speed and power
                                                    1997.
consumption versus supply voltage. Fig. 9
                                                    [2] T. Kamoto, N. Adachi, and K. Yamashita,
shows the outputs of the first control and the
                                                    “High-speed multi-modulus prescaler IC, ” in
divide-by-2/3 blocks at 1.4 GHz frequency.
                                                    Fourth IEEE International Conference on
                                                    Universal Personal Communication. Record
5. Conclusion                                       Gateway to the 21st Century, pp. 325-328,
                                                    1995.
A low power programmable divider for DRRS           [3] M. H. Perrott, T. L. Tewskbury, and C. G.
standard in 1.4 GHz frequency band has been         Sodini,      “A       27mW         fractional-N
presented. With 25% duty cycle of the output        synthesizer/modulator IC, ” in Proc. IEEE
of the first divide-by-2/3 blocks, the constraint   Solid-State Circuits Conf., San Francisco, CA,
for high-speed operation is relaxed. In order to    pp. 366-367, Feb. 1997.
reduce the delay time, a new embedded AND           [4] N. Krishnapura, P. Kinget, “A 5.3 GHz
gate in the D-FF, was also used in the first        Programmable Divider for HiPerLAN in
stage. Simulation results demonstrated the low-     0.25µm CMOS, ” IEEE 25th Europan Solid-
power consumption at the target frequency.          State Circuits Confrence, Duisburg, Germany,
Table. 1 presents recent publications on high-      pp. 142-145, Sep. 1999.
speed frequency dividers, designed with the         [5] B. Razavi, Kwing F. Lee, and Ran H. Yan,
phase switching technique. In comparison to         “Design of high-speed, low-power frequency
[3,7], the power dissipation has been very          dividers and phase-locked loops in deep
decreased. In [4], the divider was designed in      submicron CMOS, ” IEEE JSSC, Vol.30,
0.25µm process so that the maximum                  No.2, pp. 101-109, Feb. 1995.
frequency was increased to 5.5 GHz, however         [6] H. Wang, “A 1.8V 3mW 16.8GHz
the power consumption at 2V power supply            Frequency Divider in 0.25µm CMOS,” IEEE
and 950MHz operation frequency is nearly two        ISSCC, pp. 196-197, Feb. 2000.
times more than the power consumption of this        [7] J. Craninkx and M. S. J. Steyaert, “ A
work.                                               1.75GHz/3V dual–modulus divide-by-128/129
                                                    prescaler in 0.7µm CMOS, ” IEEE JSSC,
                                                    Vol.31, No.7, pp. 890-897, July. 1997.
       P1
D0*                                            CK                                                                              CK




                                                                                          QA_0                          QB_BAR_0
                                       QB_BAR_0                             QB_0


                                                                                                                                                                  QB_0


                                                                                                                                                                  QA_BAR_0



                                        CK_BAR                                                                     CK_BAR



                                       QA_BAR_0                             QA_0                         QB_BAR_0                                          QB_0




                                                    Fig. 6. The first divide-by-2/3 block with 25% duty cycle



                                                                                                                                                                 QB_1
                                              QB_BAR_1
                                                                              QB_1      D1*_BAR                         QA_1
                                                                                                                                QB_BAR_1

                                                   D1*                                                                                                        QA_BAR_1

                                                           OUT_0_BAR                                                                       OUT_0_BAR



                                                             OUT_0                                                                           OUT_0




                                          QA_BAR_1                               QA_1
                                                                                                                           QB_BAR_1                                QB_1




                                                              OUT_0
                                                                                                                                              OUT_0



                                                          OUT_0_BAR
                                                                                                                                           OUT_0_BAR



                                                         Fig. 7. Other divide-by-2/3 blocks with 50% duty cycle
                                        1.9                                                                              45
                                        1.8                                                                              40
            Maximum Frequency (GHZ)




                                        1.7
                                                                                              Power Dissapiation (mw)




                                                                                                                         35
                                        1.6
                                                                                                                         30
                                        1.5
                                                                                                                         25
                                        1.4
                                                                                                                         20
                                        1.3
                                                                                                                         15
                                        1.2
                                        1.1                                                                              10

                                           1                                                                              5

                                        0.9                                                 0
                                               2            2.5        3   3.5      4         2                                             2.5        3   3.5            4
                                                                                 Power Supply (v)
                                       Fig.8. Maximum frequency and power dissipation versus power supply
      3V

      0V
                                      V (c k )
      3V

      0V
                               V (Q B _ 0 )
      3V

      0V
                               V (O U T _ 1 )
      3V

      0V
                            V (O U T _ 3 )
      3V

      0V
            15ns                                                                                                                                                              45ns
              V (D 0 * )
                                                                Fig.9. Waveforms of the divider at 1.4 GHz

								
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