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BQ76930: OCD and SCD trigger at same time

Chen Alex
Prodigy 55 points
Part Number: BQ76930

Hello,

In our project we are measuring battery status with bq76930, but currently we found that

when Over-current in Discharge (OCD) is triggered, immediately Short-circuit Discharge (SCD) is also

triggered. Does anyone know why and has solution to this question?

Thank you.

  • 0
    TI__Guru 54715 points
    Hi Chen,
    If the current exceeds both the OCD and SCD thresholds, the SCD will cause DSG turn off. If the current persists for the OCD time, the OCD time will also be set.
  • 0 in reply to WM5295
    Prodigy 55 points
    Hi WM5295,

    Thanks for the reply.
    Our AFE settings for OCD and SCD are different, the threshold for OCD is 200A and for SCD is 220A. So we expect that when OCD threshold is reached, OCD shall cause DSG to turn off.
    But currently OCD and SCD are triggered at same time.

    Thank you.
  • 0 in reply to Chen Alex
    TI__Guru 54715 points
    Hi Chen,
    The accuracy of the OCD and SCD thresholds is expressed as with OCOFFSET and OCSCALEERR, so an overlap of the thresholds is not expected. The part responds to the voltage at the sense inputs. You might check the performance of the part with an applied voltage stepping the voltage slowly to observe the OCD and SCD thresholds. Be sure the part is working as expected and is not damaged.
    Also look at the response time from the applied voltage to the DSG off, the status register read comes much later of course.
    With the real currents check the voltage at the sense pins, be sure the sense resistor is not heating during the OCD event to raise the voltage to the SCD level. Checking the response time from current application to DSG and comparing to the results of the voltage test may indicate whether the OCD time is being terminated by a faster SCD.