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BQ78350-R1A: Activation of protection lasts much longer than delay time.

Jakub Pykacz
Prodigy 10 points
Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hi, 

I have two problems that refer to overcurrent protection. The first one is that I set in bqstudio delay time to 5s (charging and discharging overcurrent protection - ODC, OCC) , but FETs are turned off after 6-7s after exceeding threshold value. The second problem is that I set threshold of overload in discharge protection (AOLD) to 5.5 A and delay to 160 ms, but pritection is triggered only after exceeding 5.9 A.In this protection, activation time is proper and FETs are turned off exactly after 160 ms. I found out that hardware protections like ASCD or AOLD have their own comparators, but in case of discharge and charge overcurrent (ODC & OCC) use the 16-bit modulator. What do you think about it?

Thanks in advance.

  • 0
    TI__Guru 56046 points

    The gauge runs the FW protection (OCD, OCC) in its one-second period processing loop so there will be up to 1 second additional delay as the processing loop isn't synchronized with your test timing. The data comes from the delta-sigma coulomb counter ADC.

    The ASCD and AOLD protection use a HW comparator (which checks the voltage on SRP-SRN) so these are much faster (160ms) but not as flexible (only a few fixed thresholds).

  • 0 in reply to Dominik Hartl11
    Prodigy 10 points

    Thanks for your reply. Do you have any clues what can causes triggering AOLD protection after a higher threshold (5.9A) than the one set in the cofiguration (5.5 A).

  • 0 in reply to Jakub Pykacz
    TI__Guru 56046 points

    The threshold is a voltage threshold. The current calibration doesn't apply to this threshold so the current will be off if your sense resistor isn't super precise.