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BQ76952: Is there a way to check if the bq76952 is reliable for current sensing?

seongcheon kim
Prodigy 60 points
Part Number: BQ76952

Tool/software:

hello.
I would like to inquire about the functions of bq76952.

Can bq76952 recognize that the current sensing input value is abnormal and activate PF or protection functions?
For example, when the overcurrent protection setting value is 20A,
In normal conditions, the protection function is activated by recognizing 20A, but if what should be recognized as 20A is recognized as 19A due to external factors,
Is there a function to recognize errors in current sensing values ​​and perform PF or protection operations?

Thank you as always for your kind answers.

  • 0
    TI__Mastermind 42060 points

    Hello Seongcheon,

    The part does have multiple PF and protective functions (all listed in the TRM), but not quite what you are asking for.

    That sounds like a strange test case here. The part will respond based on what the voltage on the SRP/SRN pins are, noise should be filtered by this point to get accurate measurements. 

    If you would like to have multiple cases of protections, just in case, that is possible. There is OCD1/2/3, all which can be adjusted to different thresholds and delays.

    OCD1/2 are comparator-based current protections, while OCD3 is a digital-based protection, meaning that it will protect based on the digitized CC1 current. 

    Since these are separate types of protections and you want some redundancy, you could potentially set OCD1 and OCD3 to the same protection value, so that each independently checks the currents to make sure a protection happens when it is supposed to. 

    Additionally, you could set OCD 2 to a different threshold and delay, for example you could set it at 18-A instead for a much longer delay time than what OCD1 would be.

    We also have the following FAQ that explains the differences between OCD1/2/3 and SCD, which may be useful:

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 60 points

    Thank you for your answer.
    So, what is the algorithm for the bq76952 to measure both ends of the sensing resistor and convert the received value into current?
    Do I convert the measured voltage value into current by dividing it by the internally calibrated resistance value?

    thank you

  • +1 in reply to seongcheon kim
    TI__Mastermind 42060 points

    Hello Seongcheon,

    For comparator-based current protections (OCC/OCD1/2 and SCD), the part looks at the voltage of the pins to make current protection decisions, you'll see the units of protections here are in mV. 

    For OCD3, which is a digital-based protection, it will look at the reported digitized CC1 value and use this for protective decisions, which is in units of userAmps. The current calculation is done automatically by the BQ76952 which by default is set to work with 1-mOhm sense resistors. If using a different value resistor, the current calibration values must be changed, this is described in Section 4.12 Current Calibration of the TRM.

    Best Regards,

    Luis Hernandez Salomon