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TPS61200: TPS61200

Andrew Tyson
Prodigy 10 points
Part Number: TPS61200
Other Parts Discussed in Thread: TPS62100, TPS61299

Tool/software:

Hi,

We are using the TPS61200 to regulate a 3V7 Lithium Polymer pouch cell (VBATT) to 3V3 to power a microcontroller.

We also have a USB-C connection for flashing the microcontroller and to recharge the cell through an MCP73831 charge controller.

The issue is when you unplug the USB-C the TPS61200 shuts down and won't power back up.

Power cycling the battery allows the TPS62100 to turn on and function correctly, however plugging and unplugging the USB-C returns the IC to an off state.

Using a bench top power supply (in place of the cell) and dropping the power by 0.2V rapidly replicated this problem.

Any thoughts would be greatly appreciated.

  • 0
    TI__Genius 9165 points

    Hi Andrew,

    thanks for reaching out. Let me understand the application firstly. The input is 3.7V, and output is 3.3V.

    In this way, the converter doesn't work under boost mode. See the reference in datasheet: If the input voltage reaches or exceeds the output voltage, the converter automatically changes to a Down Conversion mode. In this mode, the control circuit changes the behavior of the two rectifying switches. While continuing switching, it sets the voltage drop across the rectifying switches as high as needed to regulate the output voltage. This means the power losses in the converter increase. This must be taken into account for thermal consideration.

    Anyway, the current limit will be lower and you should check the load current and see how much the inductor current  is . I doubt it is because it trigger current limit.

  • 0 in reply to Nini Zhong
    Prodigy 10 points

    Thank you for the quick response.

    Under normal use (slow discharge from device use), the TPS61200 performs as expected, it switches from Down conversion to boost mode (ULVO is set to approx 2V9).

    When running the benchtop supply at 4V1 and unplugging the USB, the device stays powered. 4V or under unplugging the USB will shut the device down.

    The inductor being used is a LQM21PN4R7MGHL with a 1.2A current rating

  • 0 in reply to Andrew Tyson
    TI__Genius 9165 points

    Hi Andrew,

    could you check the inductor current, Iout and SW waveform as I mentioned, which will be more helpful to locate the root cause.

  • 0 in reply to Nini Zhong
    Prodigy 10 points

    Measuring current across the inductor at 14.5mA.

  • 0 in reply to Andrew Tyson
    TI__Genius 9165 points

    Hi Andrew,

    How did you measure the inductor current ? From the waveform the device work in downmode, the current limit is lower than normal boost mode. That should be taken into account. Do you have any waveform for the inductor, normally it's a triangle shape.

  • 0 in reply to Nini Zhong
    Prodigy 10 points

    We measured the voltage drop across the inductor as we only have fabricated boards to work with.

    No waveform of the inductor.

    Is it looking like I have under specified the inductor, or is our load too low?

  • 0 in reply to Andrew Tyson
    TI__Genius 9165 points

    Hi Andrew,

    I suppose the inductor current isn't such low, just want to double check it. I suspect it's because current limit. Any chance to alter to other device such as TPS61299?