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BQ79656-Q1: current sense calibration in Bq79656

S Naik
Prodigy 120 points
Part Number: BQ79656-Q1

Dear Ti Team,

We are using bq79656, in same we are using shunt based current sensing. we have observed that there is error in current reading above 20/30A, it is currently giving us error of 1 to 1.8 A on value above 100A.

from data sheet we have come across register cs_adc_cal1/2. but we didnt get any application note or section regarding the same. Can any one reach out and help to calibrate /error correction of cs adc?

  • 0
    TI__Expert 7000 points

    Hello Naik,

    What is the value of your Rshunt resistor? Does the error in current measurement only occur at high current measurement? Does your current multiplied by the Rshunt fall within the recommended values? 20-30A is a large value. Also 

    Before you write to the cs_adc_cal1/2, you must see if there is an offset between the SRP and SRN pins and calibrate it accordingly. 

    Best,

          Quentin

  • 0 in reply to Quentin Silic
    Prodigy 120 points
    Quentin Silic said:
    What is the value of your Rshunt resistor?

    100uOhms

    Quentin Silic said:
    Does the error in current measurement only occur at high current measurement?

    What we observed is it starts from 20/30 Amps, after 100Amps its like +/-2Amp in errors

    Quentin Silic said:
    Does your current multiplied by the Rshunt fall within the recommended values?

    Yes, for 100Amps its 10mV.

  • 0 in reply to S Naik
    TI__Expert 7000 points

    Hello Naik,

    100 uOhm should work well in this system. It sounds like you will have to use the cs_adc_cal1/2 registers to configure the gain and offset. You already know the offset you are seeing in the system. Please refer to the register map in the datasheet for what values correspond to what offset/gains for this ADC. After configuring you should be able to see a change in the accuracy of the current measurement.


    Best,

         Quentin