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BQ29700 Wrongly Tripping

I have an application with a Li-Ion Poly battery soldered to my board.  I put BQ29700 on my circuit board to provide protection against over current (act as a resettable fuse) and undervoltage damage to the battery.  

So far I've been powering on a bench supply with 3.4V.  The BQ29700 appears wrongly not to assert DOUT to turn on the FET.  It only happens about half the time.  Am I doing something wrong with my circuit:

  • In none of my tests I've been drawing any high current.
  • Shorting across R10 with tweezers does not get it out of this mode.  
  • Pulling DOUT high sometimes gets it out of the mode, as if once current starts flowing and developing voltage across Pin 6 and Pin 4, it turns on the FET.  It could also be that pulling up DOUT has some other effect, such as briefly tripping current limit on my supply, which I've been setting in the 150mA range.  
  • Replacing the part does not work.  I've seen this behavior on three boards.  Changing out the BQ29700 didn't help.  I can't detect any shorts, and I believe there is sufficient solder on all pads.  

Can someone suggest some things to look for?

  • Charles Gervasi said:
    Shorting across R10 with tweezers does not get it out of this mode.

    Shorting across the transistor Q2 does get it out of this mode.  It's as if I must get the current flowing to jump start it.  

    I'm eager to hear any ideas or suggestions.

  • There is a Caution note in the datasheet that covers this:

    This also applies for a battery that is deeply discharge and the device gets powered off because of it. A charger would need to be connected to turn it back.

    I understand that this is an older post, but I have come across the same issue with one of my customers and I thought I could help you out as well.

  • Joe Howard said:
    This also applies for a battery that is deeply discharge and the device gets powered off because of it. A charger would need to be connected to turn it back.

    We have discovered all this, and I agree completely.  We have this part on our board as additional protection beyond the battery's protection circuit.  We really like this part.

  • Have same problem. I think the main reason i that when connecting battery, MOSFET is turned off so there is voltage difference between BAT- and GND sensing on V- pin, so BQ assumes that there is an fault state. Probably MOSFET does not turn on before pre-programmed delay. In my application i am using another MOSFET than suggested in datasheet (with less total gate charge), but i think the main problem is that gate signal in my PCB design is too long (i have not confirmed that on oscillogram yet). For now system works with 200 kOhm resistor placed beteween BAT- and GND, what forces unfortunately current flow at the MOSFET turn-off state.