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BQ40Z50: Inaccurate current measurement after a calibrated BQ40Z50 DUT been discharged

Sheldon He
Expert 8585 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQPRODUCTION, BQSTUDIO

Hi expert,

We have completed the calibration of BQ40Z50 using the HPA495A+EV2300+BQPRODUCTION and have two questions after the calibration.

Firstly, We have calibrated the current using HPA495 and DUT and got the correct value already like this:

Then we have operation are as follows:

  1. Read Srec from device;
  2. Program another new DUT;
  3. Use electronic load as load;
  4. Discharge at -2000mA;
  5. I got incorrect current value:-1984mA.

So,Why is the current inaccurate when we use an electronic load to discharge?

Could the calibrated value be applied to other scenarios with different loads?

Secondly, We used the HPA495A+EV2300+BQPRODUCTION to calibrate two DUTs and then I checked the data Memory from two DUTs with bqStudio.

DUT1:

DUT2

Different DUTs got different values.

 So,How can I use only one "**.srec" file for mass production?

Thanks

  • 0
    TI__Mastermind 24870 points

    Hello Sheldon,

    This is within reason. Did you calibrate the sense resistor? Please use the calibration plug-in in bqStudio, calibrate the srec file over the boards, average out the CC Gain/Delta values and recreate golden image.

  • 0 in reply to Kang Kang
    TI__Expert 8585 points

    Hi Kangkang,

    Yes, we already calibrate the sense resistor.

    Do all of our products calibration value must use the calibration plug-in in bqStudio instead of HPA495+BQPRODUCTION for mass production?

    What can HPA495+BQPRODUCTION help us?

    We'd also like to know the meaning of “average out the CC Gain/Delta values”. How many DUTs we need for “average out the CC Gain/Delta values”? 

    Thanks

    Sheldon

  • 0 in reply to Sheldon He
    TI__Mastermind 24870 points

    Hello Sheldon,

    I would use bqStudio for a single DUT. For multiple DUTs, thats bqProduction.

    You could try averaging across 30, this is just a suggestion. Try to calibrate so that it reports 2000 mA when you apply 2000 mA.

  • 0 in reply to Kang Kang
    TI__Mastermind 24870 points

    It could also be that your sense resistor values are drifting. Please measure voltage drop across sense resistor and make sure the temp co is not changing the resistor value by too much.