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TIDA-01093: AFE used is not stable (Bq7693002)

smash Micheal
Intellectual 1000 points
Part Number: TIDA-01093

Dear all ,

I have implemented Tida-01093 in pcb , but AFE used Bq7693002 & Bq7693006 are not stable it seems.

I think some problem is their in AFE it self.

Because after 24 hours of operation, AFE adds offset to Cell voltage readings.

Same offset is getting zero, if cell is removed and mounted again.

Why such behaviour? 

Is it AFE issue? or Hardware or Software?

Some one please comment.

Rohit

  • 0
    TI__Guru* 78803 points

    Hi Rohit,

    I have not heard of this behavior before. Can you determine if the cell voltage readings are showing variation during cell balancing? If so, you might want to try changing the cell input capacitors from 1uF to 0.22uF to reduce the time constant. 

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Intellectual 1000 points

    Balancing circuitry is not populated in pcb presently.

    Rohit

  • 0 in reply to smash Micheal
    TI__Guru* 78803 points

    Hi Rohit,

    Can you share any more details or clues about this issue. The BQ7693002 should not report a different result after removing and re-connecting the cells. Could it be a software issue in the host controller?

    Matt

  • 0 in reply to Matt Sunna
    Intellectual 1000 points

    Hi,

     

    Yes software could be an issue.

    But how to ensure who is at problem Hardware or AFE or Software?

    In order to have answer for that , i removed & remounted a cell C19 , but if software might had issue , i may not get decreasing value of Cell C19 after its removal in Debigging. But that was not the case. In Debugging i found decreasing value of Cell C19. So i confirmed software might not creating issue.

     

    But still am not sure if software is responsible or not ?

     

    Also to share with , after remounting cell C19 microcontroller read without offset value. Means before removing a cell, microcontroller was reading cell C19 with 30mv approx. offset, but after remounting cell offset vanished away.

    Attaching Excel Sheet for reference.

    time-1:40 PM 3-11-2020  
    cell Voltage by FLUKE Voltage by Capacitor Voltage by LCD Voltage by Software Delta = FLUKE - Software
    C1 3.575 3.571 3.52 3.53 0.045
    C2 3.573 3.573 3.57 3.572 0.001
    C3 3.582 3.582 3.57 3.579 0.003
    C4 3.576 3.575 3.57 3.575 0.001
    C5 3.581 3.580 3.57 3.575 0.006
    C6 3.572 3.575 3.56 3.565 0.007
    C7 3.578 3.577 3.57 3.572 0.006
    C8 3.574 3.573 3.57 3.572 0.002
    C9 3.575 3.574 3.56 3.569 0.006
    C10 3.568 3.568 3.56 3.565 0.003
    C11 3.528 3.526 3.54 3.545 -0.017
    C12 3.516 3.515 3.5 3.509 0.007
    C13 3.546 3.546 3.54 3.542 0.004
    C14 3.553 3.552 3.54 3.545 0.008
    C15 3.557 3.556 3.54 3.549 0.008
    C16 3.554 3.556 3.57 3.571 -0.017
    C17 3.553 3.553 3.57 3.574 -0.021
    C18 3.543 3.542 3.56 3.565 -0.022
    C19 3.545 3.544 3.56 3.566 -0.021
    C20 3.546 3.543 3.56 3.566 -0.02

    Also U7 I2C Isolator used in Tida-01093 design is permanently powered ON as I have used different AFE parts.

    Bq7693003 & Bq7693006

    RohitCell Voltage measur result sharing.xlsx

  • 0 in reply to smash Micheal
    Intellectual 1000 points

    Hi,

    I found problem from software itself.

    Now working perfectly.

    Now only problem remains is of Upper AFE Fast Discharge compared to Lower Afe in Tida-01093 Design.

    So no problem of AFE found .

    Thanks.

    Rohit