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BQ78350 disable ALERT signal on BQ769x0

Other Parts Discussed in Thread: BQ76940, BQ78350

Hi,

We are using the BQ78350 with the BQ76940 and the documentation for the BQ769x0 says that we need to write to the SYS_STAT register to clear the bit that set the ALERT pin.

The 0x58 SBS command from the BQ78350 does not work since it is a read-only register.


How would I reset the bits so the ALERT signal is cleared?

Regards

  • The bq78350 will automatically write the bq769x0 status register to clear the fault.  The ALERT is set with the CC ready signal also, the bq78350 clears this on its own timeline, so the dutycycle of ALERT will vary.

    If ALERT never clears, check the status and determine the cause of the permanent fault.  Also check that the pin does not have an excessive capacitance, the maximum recommended time constant on the pin is 250 us.

  • Indeed, the duty cycle varies. It goes from 0 to almost 100% over a 20 seconds period, duty cycle increasing at about each 250ms.
    It is stated in the BQ76940 datasheet to avoid leaving ALERT pin high since it drains the lower stack part (cells 1-5) only and can induce cells unbalance.
    What do you reckon?
  • Balancing would be good with this device version.