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									                      NRL SECCHI EEPROM
                      Issues & Resolutions

                                Amy Hurley
                              NRL CODE 8242
                               202-767-6620
                         ahurley@space.nrl.navy.mil


10/12/2005 EEPROM.1
                               SECCHI EEPROM HISTORY
       • NRL designed, fabricated, tested and delivered 2 Flight SECCHI Electronics Boxes (SEB) – FMA
         and FMB for the SECCHI instrument/STEREO mission
       • Each SEB contains:
               – Quantity 24, 128K X 8 EEPROM (Austin Semi part # 5962-3826718QNA (AS58C1001SF-
                 15/883C)) on the 1553 card for flight software application code
               – Quantity 3, 128K X 8 EEPROM (Maxwell part # 28LV010RPFS-20) on the RAD750 processor
                 board for boot code
               – Both use Hitachi die
       • To date NRL has not had problems with the EEPROM devices resident on the RAD750 card
               – BAE has delivered documents stating that some users have seen the intermittent behavior
       • During lab & TVAC testing we encountered problems that after much investigation were
         determined to be related to intermittent readout on some of our EEPROM devices on the 1553
         card
       • Summary of devices with problems:
               – U37 – LDC0249 – APRIL 2004 - FMA unit – data readout stability issue found in lab testing. Replaced and
                 no failures (APR 2004). Later found device manufacturing/quality issue.
               – U25 - LDC 0208 - MAY/JUNE 2004 – FMA unit – boot problems in TVAC with FMA. Testing with JTAG
                 isolates problem to a page area (intermittent readout just like U32). Once device written to as part of
                 testing the problem stops occurring (did days worth of 24/7 read back tests with zero failures). Later tested
                 by Austin as well. Part replaced.
               – U32 – LDC 0249 – JUNE 2004 – FMB unit - had issues in lab testing. Isolated to specific page of U32. Board
                 testing showed oscillatory nature of readouts – see SEI scope traces. Board inspected by QA – nothing
                 found. Part replaced and no failures. Later tested by Austin as well.
EEPROM 10/12/05.2
                                                                  SEB Block Diagram



                                     Spacecraft Decontam Heater Power




                                                                                                                                                                                                         Guide Telescope Gain/Red CMDs
                                                                                                    Operational/Decontam Heaters




                                                                                                                                                                              SCIP Door Motor Commands
                                                                        CCD, SCIP &HI Thermistors




                                                                                                                                                                                                                                         SCIP/HI Door Encoder Bits
                                                                                                                                                                                                         Guide Telescope Voltages




                                                                                                                                                                                                                                                                                                                          Spacecraft 1553 Bus B
                                                                                                                                                                                                                                                                                                  Spacecraft 1553 Bus A
                                                                                                                                                        MEB 2ndary Voltages
                                                                                                                                   GT 2ndary Voltages
                                                                                                    Calibration LEDs




                                                                                                                                                                                                         Serial I/F to MEB




                                                                                                                                                                                                                                                                                                                                                     JTAG Test I/F
                                                                                                    CEB Power




                                                                                                                                                                                                                                                                                 SCIP CEB
                                                                                                                                                                                                                                                                        HI CEB



                                                                                                                                                                                                                                                                                            GSE
            Chassis Cavity
             Power Supply                                    Power                                                                                                                                                                                                           Space
                                                                                                                                                                   House Keeping                                                                                                                                                                   RAD750
               Interface                                    Interface                                                                                                                                                                                                         Wire                1553
                                                                                                                                                                      Board                                                                                                                                                                       Processor
                 Board                                        Board                                                                                                                                                                                                           Board               Board
                                                                                                                                                                       (HKP)                                                                                                                                                                        Board
                 (PSIB)                                       (PIB)                                                                                                                                                                                                          (SWIC)
                                                                                                                        +3.3V, +5V,
                             Bus                                                                                                                                                                                                                                     cPCI
                                                                                                                        +/-15V
                             Power
                             Secondary                                                                       CMD/TLM/”Pass Throughs”                                                                                                                                        Proc Thermistor
                             Power

            Items Generated on PIB and Go Out Through HKP I/O
            Items Come in Through PIB I/O & Get Routed to HKP                                                                                                                                                                                                                    * SEB Is Single String
EEPROM 10/12/05.3
                                       Device History – U37
  • Resident in FMA unit - LDC0249 – problem first arose April 2004
  • APR 2004:
           – FMA has data read out issue on all bits with EEPROM during lab testing. Isolated to U37
             (LDC 0249). Board inspected & device replaced. Functioned properly thereafter. No other
             statistics are known.
  • JUN 2004:
           – U37 sent to Austin Semiconductor for testing in their in-house screening test fixture
                    - U37 is deemed non-functional. Several leads have continuity issues. Parts sent back to
                      NRL.
  • JUL 2004:
           – Failure analysis performed on U37 by OSC at Dulles facility (bond pull test performed per
             MIL-STD-883B, with pass/fail criteria per method 2011.7, paragraph 3.2, and a SEM
             performed per MIL-STD-883B, with pass/fail criteria per method 2018 paragraph 3.7.2)
                    - Failed gross leak test – seal voids were found – many leads corroded – see next slide
                    - Analysis shows internal contamination contains Chlorine – this would be found in
                      commonly used PWB cleaning agents/detergents. During cleaning the detergent
                      penetrated the voids
                    - Parts traceability paperwork reviewed – all required screening was performed on our
                      devices. Don’t know how this part got through
                    - This device taken out of intermittent signal investigation since problem was
                      manufacturing/quality issue
  • All EEPROM devices installed on boards were visually inspected to ensure no other parts had a
    similar flaw
EEPROM 10/12/05.4
                    U37 Failure Analysis Results

                    Void




                                  Green/white residue contained corrosive element chlorine




EEPROM 10/12/05.5
                                           Device History – U25
    • Resident in FMA unit - LDC0208 – problem first arose May 2004
    • MAY-JUNE 2004:
            – FMA has boot issues during TVAC testing. Insufficient insight into RAD750 operations in TVAC chamber to
              debug – completed cycles. No temperature relationship found to exist however.
    • JUNE 2004:
            – Post-TVAC FMA debug testing of FSW booting performed. Problem is isolated to 2 bits of a specific page
              on U25. Problem intermittent, identical to FMB U32 problem
            – Extensive testing performed:
                    - Special unique patterns written in order to try to isolate all failing bits and read back during 24/7
                      testing for days. No failures. [Didn’t realize problem would go away once we wrote to the memory
                      devices]
                    - Put FMA 1553 card on extender to assess the signals on the EEPROMs for noise, glitches, etc during
                      normal operations as well as power up/down
                        -   Everything nominal
                    - Attempted to recreate TVAC scenarios during test – ran for several days without read back failure
                    - Wrote all zeroes (believed to be best to use in detecting weak writes) to both lower and upper banks of
                      EEPROM on FMA, using the violated timing on page writes of 8ms, instead of the required 10ms, in an
                      attempt to simulate a “weak write”
                        -   Ran looping read back tests for several days – no failures
                    - Carefully used freeze spray on U25 device to see if being cold would cause a failure since the issue
                      started at cold during TVAC – no read back failures created by this
                    - Loaded special test pattern recommended by Aerospace white paper [1] and ran thermal tests (-23C to
                      +47C) but could not get read back failures. Several hours of soak, run over many days
    • Once device was written we could not recreate the page failure
    • Device replaced on flight board and recommendations in summary implemented

EEPROM 10/12/05.6
                                          Device History – U32
   • Resident in FMB unit - LDC0249 – problem first arose June 2004
   • JUNE 2004:
           – FMB has an intermittent read issue with EEPROM during lab testing. Isolated to a specific page of U32
             (LDC 0249). Board sent to FL for debug.
           – FMB-1553 board testing in FL – scope traces taken showing oscillatory nature of certain EEPROM data
             outputs on U32 during read cycle. Intermittent nature of problem due to this oscillation (see Greg’s charts)
           – FMB board received at OSC for inspection/cleaning. Nothing found so U32 was replaced. No failures
             afterwards.
           – U32 device sent to Austin Semiconductor for testing in their in-house screening test fixture
                    - U32 was tested successfully and was deemed w/in specs. Traces were taken to simulate our chip
                      access timing. Suggestion made to change the relationship of OE* to CS* to avoid the output switching
                      glitch visible on data outputs for brief period of time. We were not operating the part inconsistent w/
                      the data sheet, but our timing was thought early on to possibly be allowing/exacerbating the ringing
                    - Note: this part Was Re-Written Prior To Removal & shipping to Austin, during debug testing
           – Performed investigatory tests on FMB chassis by modifying both the page and word write time required by
             the EEPROM. Sometimes write was successful, sometimes only every other page would be written,
             sometimes certain bytes were skipped, depending on what you altered and how far from the required time
             you had deviated.
           – Numerous power on/off cycles performed while monitoring the EEPROM Reset and Write lines to monitor
             for any glitches. Nothing out of spec found.
   • JULY 2004:
       – U32 Installed on unused GLAST board for continued testing
       – Voltage Tests Were Conducted To See If Problem Could Be Recreated With Lower Vcc Voltage
       – Could Not Recreate The Page Failure



EEPROM 10/12/05.7
                                          Additional Investigations
    •    Found errata sheets/application notes on Maxwell’s site [2] related to these devices stating a bit flip/intermittent problem had been seen
         by a few users. Hitachi’s answers to questions posed by user’s are sketchy at best. In all cases the problem was resolved by re-writing
         and/or mapping around the problematic area
    •    Had telecon with Dr. Doug Sheldon, JPL parts engineer somewhat familiar with MER issues, but EEPROM in general. He sent 2 JPL
         internal white papers and recommended how they handled the problems they had with these devices: 1) use of the chip’s internal
         “software protection mode” which ensures the charge pump is good and ready for a write cycle, 2) perform many write cycles (500) to
         avoid “weak writes”, 3) use of redundant code locations – identical copies of code stored in multiple memory areas spanning unique
         devices
    •    Received email &voicemail from Yuan Chen, JPL parts engineer associated with MER and other programs. She recommends what they
         did to handle their problems with these devices: 1) redundancy of code – code stored in multiple locations, 2) the use of EDAC, 3) an
         “on-board” screening of the devices by reading from them 1000-2000 times (note: the overnight EEPROM read tests we have been
         looping on results in the EEPROMs having been read 10’s of thousands of times, so we are exceeding this recommendation), and 4)
         map around any parts that have had issues.
             –      Additional information from her white paper [3]: They determined that “weak cells” were their root cause, which they believe are
                    caused by either process induced defects or poor programming. They did a lot of testing on data retention, and modified the
                    charge pump voltage to simulate weak cells for study. They performed diagnostic write/read cycles to emulate weak cells and
                    demonstrated that weak cells can fail earlier than a properly programmed cell.
    •    Had phone discussion with Aerospace white paper “Experiences in Qualifying a Commercial MNOS EEPROM for Space” author, Elliot
         King [1]
             –      An intermittent failure was found with 2 devices during the testing being performed for qualifying EEPROMs. In 1 case the failure
                    resolved itself after a couple of hours, in the other case it lasted 2 days then resolved itself. They determined the failure was
                    sensitive to the device power supply, consistently failing at less than 5.00V. It was only specific addresses in the part that failed
                    not all. A screening plan was generated to weed out such early failing parts. One of the criteria important in forcing a failure they
                    found was the pattern programmed into the EEPROMs and the order in which you read it out. We have attempted to simulate this
                    pattern in the patterns being mentioned above as used during our overnight read tests.
             –      Mr. King stated that Hitachi was not forthcoming in helping them resolve this problem.
             –      He stated that the oscillations they saw on the outputs always died out on their own, given sufficient time, and that one of their
                    resolutions was to extend their Read time so that the sampling would occur after the oscillation had damped out
             –      Additional details about the intermittent problem they saw was that only a subset of addresses failed in the device (similar to our
                    page issues) and that the oscillations “suggest that there may be an occasional combination of degraded memory transistor and
                    sense amplifier that produces an instability of the overall data readout behavior.”
    •    Through Austin we attempted to get internal die connectivity/schematic and other detailed device information to attempt to determine
         root cause. Hitachi was unwilling to provide documentation or a POC to Austin




EEPROM 10/12/05.8
                                        Findings Summary
       • Our EEPROM intermittent problems were related to an oscillatory readout problem contained
         within a page of the device
       • Root cause of this oscillation never determined
       • A data value of “0” always failed to a “1”
       • We ran tests to try to determine a root cause or contributing factor but no problems found:
               – Temperature:
                    - Initial failures ran the gamut – failures occurred at hot, cold and ambient conditions
                    - Temperature cycling performed and cold spray used to try to re-create the problem to no
                      avail
               – POR Operations:
                    - Numerous on/off cycles performed - could not recreate the problem
               – Vcc:
                    - Configured special tests to lower Vcc - could not recreate the problem
               – Write timing:
                    - Performed many special write cycles violating various combinations of page/word write
                      timing and could not recreate the problem
       • This problem spans more than one LDC – not LDC related
               – Note: our parts as procured to SMD part # did have the data retention bake screen
                 performed 100%
       • Once the intermittent problem occurs, writing to the device “resolves” the problem for TBD
         days/months/years
EEPROM 10/12/05.9
            NRL Final Recommendations/Plan Implemented

       •       We reviewed many industry findings/recommendations. We applied that information to our findings and generated this list of recommendations to
               follow internally. Not all of these could be applied to the SECCHI design given the maturity of the hardware at the time


       •       NRL Recommendations when utilizing EEPROM:
       1.      Ensure that the CS* to OE* timing on the devices is such that no glitches are present on the data output pins
               when the outputs are switching and the part is enabled (make sure CS* is asserted sufficiently long enough
               before OE* is asserted so that this glitch does not get through) ^
       2.      If flight parts are already resident on a board, perform an on-board screening process which involves writing
               all zeroes to the memory and reading it back and verifying the data on the order of one to two thousand times
               ^
               –     Add something like this to device screening at vendor site before delivery in future
       3.      Have the capability to map around bad areas of memory
       4.      Extend the READ cycle as long as possible, as some saw the oscillatory nature of this problem decay,
               allowing for the completion of a successful READ if it was sufficiently delayed ^
       5.      Utilize the software protection mode feature of the EEPROM device
       6.      Have EDAC protection on the code in EEPROM ^ (SECCHI has SECDED which won’t help w/ a page problem)
       7.      Have redundancy in the code in EEPROM – multiple copies spread over the memory addresses, and over
               unique physical devices/pages ^
       8.      Write more than once when “loading” critical code to EEPROM to ensure strong cumulative charge in cell ^
       9.      Modularize flight software so that code can be more easily re-loaded on-orbit if a problem is determined ^
       10. Perform a periodic check sum on the EEPROM code, downlink that checksum, and if during the comparison
           on the ground any problems are found, re-load the effected/corrupt portion of memory ^



EEPROM 10/12/05.10
                                          References

       • [1] “Experiences in Qualifying a Commercial MNOS EEPROM for Space”, E.E. King, R.C. Lacoe,
         G. Eng, and M.S. Leung, The Aerospace Corporation, 2350 E. El Segundo Blvd., (310)336-7898,
         everett.e.king@aero.org
       • [2] “1 Mb EEPROM Single Bit Errors” and “Hitachi 1 Mb EEPROM – Hitachi Die HN58C1001”,
         Maxwell Technologies Application Note, www.maxwell.com
       • [3] “EEPROM Bit Failure Investigation”, Yuan Chen, Rich Kemski, Leif Scheick, Frank Stott, Duc
         Nguyen, Tien Nguyen, Richard Bennett, Ken Erickson, Jet Propulsion Laboratory, California
         Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109




EEPROM 10/12/05.11

								
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