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BQ76952: Protection delay is over setting

Statham Su
Genius 4990 points
Part Number: BQ76952

Hello Sir:

We are testing the OCD function and we find that delay time is not match our setting.

We set the delay time is 127*3.3 + 6.6= 425.7ms.

And the tested result is 472ms.

Please refer the figure as below.

Test the OCC protection that delay time is matching our setting.

We set the delay time is 127*3.3 + 6.6= 425.7ms.

And the tested result is 422.5ms.

Please refer the figure as below.

The other we provide the gg file for you reference.

Please help to provide the recommendations for us and let us know how to meet the delay time?

Thanks a lot.20201225.gg.csv

  • 0
    TI__Expert 5090 points

    Hi Statham,

    This may be related to your CHG FET Protections A and DSG FET Protections A settings.  See the note below from p36 of the TRM:

    I see in your gg file that your settings do not match these cases.  You might try changing these values and see if it fixes the issue.

    Thanks,

    Terry

  • 0 in reply to -Terry
    Genius 4990 points

    Hi Terry:

    Thanks a lot your recommendations.

    We checked the gg file again and we saw that we setup DSG Protection A to A4.

    That A4 means except OCD2, the other protections has no delay time.

    And we setup Enable Protections A to BC, that BC means we disable the OCD2.

    According that two parameters we think that we have did right parameters. Am I right?

    Is the reason let delay time wrong that we setup the same protection values of OCD1 and OCD2 ? 

     

    Please provide your recommendations for us.

    Thanks a lot.

  • 0 in reply to Statham Su
    TI__Expert 5090 points

    Hi Statham,

    Here is what I tried to paste last time, it didn't show up then (from p36 of the TRM):

    For the CHG FET turnoff action to occur immediately when a fault is detected, the value of Settings:Protection:CHG FET Protections A should only be set to 0x18 or 0x98. Setting it to other values can cause FET turnoff action to be delayed by up to 250 ms in NORMAL mode or 1 second in SLEEP mode.

    For the DSG FET turnoff action to occur immediately when a fault is detected, the value of Settings:Protection:DSG FET Protections A should only be set to 0x80 or 0xE4. Setting it to other values can cause FET turnoff action to be delayed by up to 250 ms in NORMAL mode or 1 second in SLEEP mode.

    You might change these settings to these specific settings, to see if the delay is then as expected.

    These are separate from the value of the delay and threshold that you used.  It isn't typical to set the thresholds and delays the same, although I don't know that will cause any problem.

    Thanks,

    Terry