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BQ24780S: BQ24780S

Liangyu_Ge@asus.com
Prodigy 100 points
Part Number: BQ24780S
Other Parts Discussed in Thread: BQ24780

Hi,I am from ASUS SZ NB POWER Team.We have some questions about bq24780 now.Our protection use the independent comparator of bq24780(when CMPIN pull high,CMPOUT pin's output is low,our protect will be enable).We find independent comparator doesn't work at the second protection .

we can find COMPOUT pull  low when COMPIN is up to 2.3v at the first time.COMPOUT pull high only if COMPIN is under 2.3v.however,when COMPIN pull up to 2.3v again,COMPOUT doesn't

pull low.Can you give a reason for this? And we want to know the independent comparator's working conditions.

Thanks!

  • 0
    Prodigy 100 points

    The question happens after ACFET/RBFET  latch  off.There is a test waveform picture.

  • 0 in reply to Liangyu_Ge@asus.com
    TI__Genius 11850 points

    Hi,

    In normal operation, the independent comparator should continue working. One possible condition that can cause CMPOUT to stay fixed to the logic high voltage is ACOVP (input overvoltage), which has a rising threshold of 26 V. In the waveform below, I set VIN = 20 V and toggled CMPIN between 2 V and 3 V. CMPOUT behaved as expected until I set VIN = 27 V and entered ACOVP. At this point, ACFET and RBFET latch off, causing VSYS to decay to 0 V, and CMPOUT is fixed at logic high even though I continued to toggle CMPIN.

    I'm not entirely sure what your labels for the blue and pink waveforms mean, but if the blue waveform is VIN, then this would explain the CMPOUT behavior you're seeing. After the blue waveform rises above 26 V, CMPOUT is fixed at logic high.

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Prodigy 100 points
    Thanks for your answer