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BQ76907-Q1: Accuracy Issues in Current Measurement.

Embedded Developer
Intellectual 345 points
Part Number: BQ76907-Q1
Other Parts Discussed in Thread: BQ76907

Tool/software:

Hello, 

We are facing issues in the current measurement using BQ76907. On flowing exactly 100 A of current through the sense resistors, we are getting some 120-125 A of reading even after current calibration. For sense resistor, we have connected ten 1mOhms resistors in parallel. The kelvin connections  of these resistors are as shown:

Could you please let me know if there is any problem in this layout, or like what could be other potential reason in our case. 

Please suggest what you think?

  • 0
    TI__Intellectual 850 points

    Could you get a voltage measurement of the kelvin connections to the SRP/SRN filter network? This would help isolate the inaccuracy between the sense resistors layout or the BQ76907.
    Ideally the SRP/SRN filter network should be seeing 10mV IR drop with your setup of exactly100A across ten1mOhms resistors in parallel.

  • 0 in reply to Gavin Long
    Intellectual 345 points

    Here is the kelvin connection voltages for each shunt for 95A continuous current, we have assumed the left most shunt as the shunt 1. 

    Shunt No. Voltage Across Shunt (mV)
    1 11
    2 10.1
    3 9.6
    4 9.7
    5 9.5
    6 9.6
    7 9.7
    8 9.8
    9 10.6
    10 10.2