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BQ20Z655-R1: What is the accuracy of setting the time of BQ20Z655-R1 protection delay time ?

Billy Xu
Intellectual 490 points
Part Number: BQ20Z655-R1


Hi Sir ,

When set the over current protection delay time ,for example ,the delay time is set to 2s ,What is the accuracy of setting the time?

The delay time  accuracy is 15.25us  ,is right?

The protection circuit propagation delay is always 50us ,Regardless of the protection status, this is determined by hardware.

thanks ！

  • 0
    TI__Mastermind 42535 points
    the fw based delays will have both the delay in the df plus any time the fw scheduler takes for internal processing, which may be an additional 1s. your fet turn off time depends on the rc of the fet path.
  • 0 in reply to Batt
    Intellectual 490 points
    Hi Batt，

    I used BQ20Z655-R1 for batterys , our sw setting the over current protection delay time 2s , but the test result is about 2.9~5.8 s .
    Different chip the delay time test results are different, what's the max delay time between chip and chip ?
    If we set the delay time is 2s ,how to define the test rang?
    attchement our delay time test result,
    SN delay times with 5A（Normal 2s ）
    20180827001 4.6106
    20180827002 3.5476
    20180827003 5.206
    20180827004 4.1293
    20180827005 4.2468
    20180827006 4.8293
    20180827007 4.4217
    20180827008 3.8093
    20180827009 3.243
    20180827010 3.4054
    20180827011 4.3799
    20180827012 7.5189
    20180827013 4.7442
    20180827015 4.8027
    20180827016 5.5874
    20180827017 3.6403
    20180827018 4.5985
    20180827019 4.8109
    20180827020 3.0242
    20180827021 3.7646
    20180827022 2.9564
    20180827023 4.0349
    20180827024 5.8147

    Thanks !
    Billy Xu
  • 0 in reply to Billy Xu
    TI__Mastermind 42535 points
    What you are using here is a fw based protection. Depending on what the fw scheduler sees, it can act on once the condition timer starts. Assuming the worst case scenario, where the gauge is doing IT calculations (max watchdog is 1s, assume 990ms, then fw adc/cc process delay is 1s, then your delay being 2s), your max delay can be as high as 4s+ your rc delay.