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BQ76920: BQ76920: disabling balancers from hw watchdog?

Gert Vierman
Prodigy 30 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQ76942

Our design has a hardware watchdog to reset the main CPU in case the software is not responsive. This watchdog also asserts the ALERT pin to make sure the BQ switches off the FETs, which is a nice extra safety feature.

However, we found that the ALERT pin does not disable any active balancers; this means that if the CPU becomes unresponsive for whatever reason the battery can end up with any cells deep discharged by the balancer resistors.

Is there any way to disable all balancer outputs "from hardware", other than configuring the appropriate registers over I2c?

Thank you,

  • 0
    TI__Mastermind 21460 points

    Hi Gert,

    The BQ76920 cannot disable balancing automatically by itself. The FETs must be turned off by the microcontroller. The device will turn off the balancing FETs during certain fault conditions described in the data sheet (below).

     

    The BQ76942 does have autonomous balancing and can also disable balancing after a specified time period. This might be a better battery monitor for this application.

    Regards,

    Max Verboncoeur