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Original question:

BQ76952: Using TS1 and TS3 of BQ76952 to connect NCP18XH103F03RB thermistor can not collect the correct temperature through...

BQ76952: BQ76952 enters shutdown mode abnormally

wu angus
Prodigy 30 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQSTUDIO

hello

        We are using BQ76952 and there is some doubt about power under low temperature. BQ79652 will enter shutdown mode. The phenomena are as follows: 1. BQ76952 works normally at room temperature of 25℃, then put the controller into the cryogenic box, adjust the temperature of the cryogenic box to -10℃ BQ76952 normal state Read and write register is normal. If the controller is powered on or off again and the BQ76952 is operated again, the register value cannot be read or written. It can be confirmed that BQ76952 has entered SHUTDOWN MODE at this time, and is awakened by charging detection. After connecting the charger, BQ76952 still does not wake up. The NORMAL MODE can be entered only after the BQ76952 is powered on and off again after the charger is connected.

       In the experiment, Power: Shutdown register is not set by default，On the actual controller, the Stack Voltage is 48V and the Cell Voltage is 3.2V.There is no low temperature in the data sheet to enter shutdown mode。BQ76952 TS2 pin is suspended, RST_SHUT pin is always in low level state.May I ask why? Will BQ enter shutdown mode after being powered on and off again at low temperature? Can you analyze it for me?

  • 0
    TI__Guru* 81034 points

    Hi Wu,

    From your description, I do not see an obvious reason why the device would go into Shutdown mode. Here are a few things you can try to help debug the issue.

    • Confirm the device is really in Shutdown mode by measuring the REG18 pin. In Shutdown mode, this pin should go to 0V. In all other modes it should measure 1.8V.
    • If the REG18 pin is measuring 1.8V, try to determine whether the device could be in "soft shutdown" (see TRM description of soft shutdown).
    • Check for the possibility of condensation causing Shutdown. Condensation could bridge the RST_SHUT pin (if forced high for 1 second, the device will shut down) or it could bridge one of the cell voltages - this could cause shutdown if the CUDEP or Shutdown cell voltage features are enabled.
    • Check your register settings for which measurements and Shutdown features are enabled. For example, is TS2 Config set to measure a temperature without a thermistor connected? Or is the Shutdown cell voltage threshold set?
    • A conformal coating can help with any issues caused by condensation on the board.
    • It is possible to record permanent fail conditions in OTP by setting the OTPW_EN and PF_OTP bits. It may be good to enable permanent fails on one device along with these bits to see if the reason for Shutdown gets recorded.
    • Or you can start a log file from BQStudio and lower the temperature until the Shutdown occurs. The log file may be able to capture why the Shutdown occurred since it monitors all of the status registers.

    Best regards,

    Matt