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BQ76952: Protection OCC Recovery Threshold

Part Number: BQ76952

Hi,

I set the OCC Threshold to 4mV (in my case is 2.1A), the delay to 3.3ms, the Recovery Threshold to 600mA and the PACK-TOS Delta 100mV (Stack Voltage = 57.02V and TOS Voltage = 3.656V).

The protection triggers correctly and opens the mosfets. I don't understand why the error disappears and closes the mosfets with the recovery delay (5s) after reducing slightly the charge current without having reached the recovery threshold. Is there any other recovery condition other than the Threshold or the PACK-TOS Delta?

Thank you in advance!

Mohamed

  • Hi Mohamed,

    The only two mechanisms for recovery should be the recovery threshold or the PACK-TOS delta. 

    In your description you say: (Stack Voltage = 57.02V and TOS Voltage = 3.656V). For TOS, did you mean the PACK voltage?

    If the CHG FET is open, the charge current should fall to 0mA which should cross the threshold and the device should recover because your threshold is set to a positive value. The default recovery threshold is -200mA which means a discharge current would be required to recover (or PACK-TOS delta). By setting a positive current, the device will always attempt to recover after the recovery delay because the charging current is zero.

    Best regards,

    Matt

  • Hi Matt,

    Thank you for your answer!

    TOS means Top-Of-Stack, that in my case is 3.656V because I have 16 cells and the Stack Voltage is 57.02V.

    Ok I understand. So the OCC Recovery Threshold does not work like the OCD Recovery Threshold (closing the FET DSG every X time and checking the discharge current if it is below the threshold). The OCC protection is recovered from the fault when the current is discharging and not charging. Right?

    Thank you!

    Best regards,

    Mohamed

  • Hi Mohamed,

    That is correct. I have seen some users set it to a positive current because they want to recover based only on the recovery time, so that is an option if you do not want to recover with a discharge current.

    Best regards,

    Matt