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BQ2970: Design review help needed, circuit not functioning

Martin Labrecque
Prodigy 50 points
Part Number: BQ2970

Hi,

I implemented the following circuit. I noticed that DOUT is not high so the battery is cut-off. I tried with fresh battery and with a power supply, same behavior. I'm not concerned with the current or voltage protection features at this point, I just need the circuit to turn on, but it doesn't. I assembled 2 boards and both aren't working. I feel like I must be doing something wrong but I'm not sure what. Your help would really be appreciated. 

 

thank you very much, 

Martin L.

  • 0
    TI__Guru* 76230 points
    hi Martin,
    Did you try to compare your schematic to the reference schematic?

    The other side of R13 ought to be connected to vss. Even though you have S1 written on that branch connected to vss, are you sure there is indeed a connection in the layout?

    thaanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 50 points

    Hi Onyx, 

    Thank you for your reply. Yes, I based my schematic on the reference schematic. If there is a difference, I don't see it unfortunately. 

    Yes, the layout and the schematic match, so I don't know where the issue is coming from. 

    Can it be because of the specs of the n-fet that DOUT is low? There is no load on the circuit so I don't see why DOUT wouldn't be high...

    best regards, 

    Martin L.

  • 0 in reply to Martin Labrecque
    Prodigy 50 points

    Yellow line is the power supply ramp up. Blue line is DOUT. There is no activity on it. COUT goes high although it seems to be pulsating.... please the plot below, this looks strange. 

    Yellow line is the power supply ramp up. Blue line is COUT. This looks strange. 

    best regards, 

    Martin

  • 0 in reply to Martin Labrecque
    TI__Guru* 76230 points
    Martin
    Can you bypass that fuse on your board so we see if it resolves your issue. I feel the impedance of the fuse is interfering with the power going into the chip, ie the chip is not getting enough power to drive to the gates of the fets.

    thanks
    Onyx