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TM4C1231H6PM: RTC can't be saved

leo xue
Expert 1595 points
Part Number: TM4C1231H6PM

Hello,

   The RTC  of TM4C1231 can't be saved  When power up again during we test board function . About 30% failure rate for this. Would you please give your advice on this? thanks. 

  • 0
    TI__Guru 72500 points
    Can you give me some more information on the problem you are seeing? Is it that the Real Time Clock does not continue to run when main power is removed? What hardware are you using? Have you monitored the voltage on Vbat when you have this problem?
  • 0 in reply to Bob Crosby
    Expert 1595 points

    Hi Bob,

        Thanks for your support.

       System time can't be saved after several power on and down. So we suspect that the RTC can't work well.

    We tested the PIN 37 which the impedance reduce to 100Ω, but the good chip is about 1MΩ to this PIN.

    We also do the SWAP A-B, B-A, Fault Phenomenon Following Chip TM4C1231 . 

  • 0 in reply to leo xue
    TI__Guru 72500 points
    It is highly improbable that the parts are defective. It is more likely that the parts are not going into hibernation mode because of the battery voltage or the level on the WAKE pin and are then draining the battery. The levels on VBAT and WAKE must meet the datasheet minimum values. Once they drop below that value, some parts will detect a low voltage or level slightly before others.

    You did not answer my question about monitoring the VBAT voltage.
  • 0 in reply to Bob Crosby
    Expert 1595 points

    Hi Bob,

       After we installed a 3.3V battery on the circuit board, then the voltage of battery was pulled down to about 1V. The resistance of pin 37(VABT) reduce to about 100Ω.

    Now we are applying  the FA to verify this issue. thanks.