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Original question:

bq29709 Sampling?

BQ2970: BQ29707 , protection circuit

Hyukjun Im
Prodigy 100 points
Part Number: BQ2970
Other Parts Discussed in Thread: TIDA-00669, LP3988, TPS63051

I made a test board by TIDA-00669 schematic.

I measured the voltage and got V_ab :-2.8 , V_ac : 1.15, V_bc : 3.95.

I connected a regulator lp3988 at point d and it did not work.

I expected V_ac or V_ad  to be 3.95V , but it was 1.15V.  What am I doing wrong?

If I connect 3.3v buck/booster TPS63051, will it work OK?

Thanks in advance.

  • 0
    TI__Guru* 76230 points
    Hi Hyunkjun
    A regulator is not a battery. You ought to have a battery at Vad. This is a voltage and current protector for batteries and not just an over voltage protector.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    Thanks a lot Onyx.

    I put a bare Li pol battery at V_bc like schemetic. Am I wrong about the position?

    I thought a,d points (V_ad) are the both ends of battery pack with protection circuit.

    and I expected V_ad 3.9V.

    So I connected a regulator as a starting point of load.

    Thanks.

    Hyukjun

  • 0 in reply to Hyukjun Im
    TI__Guru* 76230 points

    Hi Hyunkjun
    Sorry i misunderstood your schematic. I looked at it again and i get a clearer picture. The fact that you have Vab to be 2.8V means that one or both  fets are not fully turned on. Can you capture the gate pins of the fets on a scope to see if they are fully functional. make sure the images look like those on page 22 of the data sheet. Then check the electrical characteristics of your fets to make sure the voltages are sufficient to turn them fully on.

    thanks
    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    Hi Onyx.

    Thanks for your advice and support. Problem was solved. Thank you so much.

    Hyukjun