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TPS3700: Low logic level asserted, trouble shooting

StDenits
Prodigy 30 points
Part Number: TPS3700

Hello.

When I turn on my device, the TPS3700 is set to a low level each time.

My scheme is attached to the message.
Q8 is de-soldered and wire-shorted.
Q14 is OFF. I also tried to de-solder it - no effect.

How to solve this problem?

  • 0
    TI__Genius 9375 points

    Hi StDenits,

    Do you have scope shots of the circuit? They would help diagnose the issue.

    Thanks,
    Abhinav.

  • 0 in reply to Abhinav.Sharma
    Prodigy 30 points

    @Abhinav.Sharma

    Hello.

    No, I did not make oscillograms.

    What points are you interested in?

  • 0 in reply to StDenits
    TI__Genius 9375 points

    Hi StDenits,

    I think isolating the device here to find the issue is the best course of action. As you mentioned, you tried disabling Q8 and Q14. I would then try to probe the nodes at your resistor divider outputs to see where we are still detecting an active voltage. The device seems to be detecting a low voltage. Also, why do you have an inductor connected on the Vdd line?

    Thanks,
    Abhinav,

  • 0 in reply to Abhinav.Sharma
    Prodigy 30 points

    @Abhinav.Sharma

    >Also, why do you have an inductor connected on the Vdd line?

    This is part of a 5V power filter.

    It appears that the problem was the power sequence of the 5 V and 3.3 V DC voltage regulators. Small changes need to be made and power logic revise.

    The TPS3700 works great in the case of UV (3.3 V -> 2.5 V): a high logic level is going low. Did not check OV, but should be the same.

    That's my fault. Thanks for the help.