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BQ79614-Q1: Testing the Evaluation Board with capacitors

Marzieh Karami
Prodigy 170 points
Part Number: BQ79614-Q1
Other Parts Discussed in Thread: BQ75614-Q1

Is there any issues with testing the evaluation board for BQ75614-Q1 with capacitors as cells and a DC power supply connected to the series string of capacitors?

  • 0
    TI__Intellectual 2710 points

    Hi Marzieh,

    No there should be no issues with this approach. As long as the voltage at the input pins (VCx pins) of the BQ75614 device show proper measurement, our device will measure the same voltage.

    Regards,

    Viktor.

  • 0 in reply to Viktor Tasevski
    Prodigy 170 points

    I tested the boards with capacitors in the range of uF. The voltage was almost evenly distributed in the capacitors before connecting them to the board. Voltage was distributed evenly after connecting it to the board. But once I pressed "wake up", voltage at capacitors with higher number of pins started going up and lower pins were dropping. 

    I tested the caps with the resistor string connected and this time the voltage stayed even on the capacitors. My question is that what happens internally in the IC that it discharges some caps and overly charges the others?

    Thanks,

    Marzieh

  • +1 in reply to Marzieh Karami
    TI__Intellectual 2710 points

    Hi Marzieh,

    I don't believe that the device is doing anything bad to the capacitors. There will be current flowing to the device in order to supply it through the capacitor string, while also some small amounts of leakage current (in the low uA range) to each cell monitoring pin. At the same time the power supply you have connected to the capacitor is trying to charge them, so there will be multiple currents superimposed at each capacitor in the string which will most likely cause voltage shifts.

    Regards,

    Viktor.

  • 0 in reply to Viktor Tasevski
    TI__Intellectual 2710 points

    Maybe try to simulate this in some simulation software, like PSpice.

  • 0 in reply to Viktor Tasevski
    Prodigy 170 points

    Hi Viktor,

    I think as the IC starts polling voltages, it pulls a small amount of leakage current from each cell which can drain a uF level cap. I tested with 1 F capacitors and it seems like it is working.

  • +1 in reply to Marzieh Karami
    TI__Intellectual 2710 points

    Hi Marzieh,

    Yes the current leakage on the Vc and Cb pins is <10uA so some of that current can possibly discharge the state of the caps.

    I am glad you got it working.

    Regards,

    Viktor.