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BQ76905: FET control Issues

ArTzy
Genius 17485 points
Part Number: BQ76905

Tool/software:

Hi Experts,

Customer is trying to make a BMS system using the BQ76905 chip and have following query:

We have autonomous control of the FETs working but when  try to send a command to manually turn on/off a fet the device enters shutdown mode immediately, no delay.

For more context, we're using an STM32 as a host processor and powering out of the 3.3v REGOUT. We've set both the HOST_FETON/OFF bits, turned off the LFOWD bit to stop it from going into shutdown if there's an LFO fault. We've also set the STACK/CELL_SHUTDOWN voltages to 0 and the TEMP_SHUTDOWN to high.

Could it be an issue with me using manual and autonomous FETs at the same time? Any help would be appreciated.

Regards,
Archie A.

  • 0
    TI__Genius 17815 points

    Hello Archie,

    ArTzy said:
    try to send a command to manually turn on/off a fet the device enters shutdown mode immediately, no delay

    Does the REGOUT pin measure 0V? Are there any other faults triggering? What mode is the device in before? (NORMAL, DEEPSLEEP, SLEEP?)

    Also, just to make sure, there are two different temperature protections that could cause the device to enter SHUTDOWN mode. There is

    1) Power:Shutdown:Shutdown Temperature

    2) Settings:Configuration:Power Config[OTSD} 

    While it does not sound likely, the OTSD bit is set to 0 correct?

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    TI__Genius 17485 points

    Hi Alexis,

    Good day. Here is the result from Cx:

    The device is in NORMAL mode before we send the command, no other faults triggering, and the regout reads 0V. Interestingly, when we power the STM from an STLink after it goes into SHUTDOWN, we're able to read measurements again and it shows no faults. 

    We believe that sending the FETCONTROL command causes an overcurrent. When we power the STM externally, everything works perfectly and we are able to manually control the FETs. We're just going to make a buck converter to power the STM from our 20V battery as well.

    Thanks for your help.

    73,
    Archie A.