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BQ76952: OCC Delay is not matched

Emma Wang
Expert 5190 points
Part Number: BQ76952

Hi expert,

My customer used BQ76952 in a new design and they meet some issue on the OCC function.

OCC Threshold is configured with 6 (i.e. 12mV), the OCC Delay is configured with 1 (i.e. 10ms), and the sampling resistor we use is 5 0.5mΩ-1% (i.e. 0.1mΩ/1%).
The theoretical calculation of the above configuration should be that the OCC protection should be 120A/10ms. According to the set current test, it was found that the delay exceeded the specification, which is 20ms.

But it they increase the OC current to 130A. the delay time will be 10ms.

The setting is set as below, is there anything wrong with their setting?

I see from datasheet there is a board offset can be added, could it relate to this issue?

Look forward to your reply.

Emma

  • 0
    TI__Mastermind 25760 points

    Hi Emma,

    It could be that the recommended RC filters on the SRP and SRN pins are adding a slight delay when the current is very close to the threshold.

    I recommend taking a look at the voltage between the SRP and SRN pins (as close to the pins as possible) to get a better idea of what the device is seeing. This will give a more accurate look at when the delay timer should start and when the protection should trigger.

    Regards,

    Max Verboncoeur

  • +1 in reply to Max Verboncoeur
    TI__Expert 5190 points

    Max,

    I think I found the root cause, it is caused by the OCC error. It is due to the timer getting cleared when the current dips down below the threshold briefly during the delay period.  

    BR

    Emma