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TPS563210A: Part is going in short circuit and feedback resistors are getting >100C.

vinicius albanas marcis
Prodigy 70 points
Part Number: TPS563210A

Hello team!

I'm having with TPS563210A finding the route cause of my issue and hope you can give me an idea of what I could have missed. Below is the schematic and PCB design.

This buck converter is feed with an input voltage range of 10.6V to 12.6V from a lithium-ion battery pack. The EN pin is direct connect (no series resistors) to an GPIO of an Arduino Mega 2560, which it is used to turn on and off. Also, the PG is direct connected to a GPIO of the same Arduino. The purpose of this power supply is to feed only an cellular modem 2G/3G. There is another TPS563210A to feed the Arduino, with 5V output voltage. The Arduino is flashed through USB connection.

I have tested the power supply (PS) with load transient, steady-state load and everything is looking fine. Moreover, when the system is integrated, it works fine, flashing and communicating through SMS with the network, all good.

However, for an unknown reason the PS stop working and the feedback resistors go very high temperature >100C, and the only solution for it to start working again is replacing the IC. Then, again after some time, some flashing of Arduino it smokes again and the same thing happen.

I'm out of ideas to tackle the issue, anyone has faced this problem or have any comments on it?

thanks,

Vinicius

  • 0
    Genius 3030 points

    Hi Vinicius.

    My first suspicion is the inductor. You should be aware of your inductor's current rating and current saturation.

    Take a look at the image below ( TPS563210A datasheet P14)

    Please do the related calculations and see whether the heating current (RMS current rating) of your inductor (from its datasheet) is sufficient more than calculated RMS current or not?

    Hossein

  • 0
    TI__Genius 10070 points

    Hi,

    The SS capacitor is a little large, why do you use 100nF? The schematic and layout is fine.

    I think you should solve this issue from system lever of the product.

    How many time does this issue appeared?

    Shawn

  • 0 in reply to Hossein Forouzani
    Prodigy 70 points

    Hossein, thank you for taking you time to analyze my issue. Those calculations were done before the prototype built.

    Please follow my calculations below within the inductor specs, they are under the maximum values.

  • 0 in reply to Shawn Nie
    Prodigy 70 points

    Hello Shawn, first of all thank you for your time.

    There are 2 Tantalum capacitor of 100uF at the power inputs of the modem, which are located 4 inches from the PS.

    So, I have calculated 10ms for the softstart in order to avoid inrush current. Please let me know if that is wrong.

    Yes, I think something is going wrong with the EN and PG pins, thus resulting in IC damage. It has happened 3 times and I needed to resolder new ICs with it (Soldering iron set to 360C).

    Vini

  • 0 in reply to vinicius albanas marcis
    Genius 3030 points

    Vinicius, your calculation is fine and the inductor chosen correctly. And the problem is not related to this side (inductor spec).

    Based on my experience, it's better to use an electrolytic capacitor added to ceramic one in the input filter circuit (between Vin and GND).

    For more details, take a look at this application note.

    Hossein

  • 0 in reply to vinicius albanas marcis
    TI__Genius 10070 points

    Hi,

    From the schematic, PG is connected to Vout via a100kohm pullup resistor. Is it not like that for your bosrd？

    A resistor should be used to pull up PG high.

    Shawn

  • 0 in reply to Hossein Forouzani
    Prodigy 70 points

    Hello Hossein, again thank you for your insights.

    Indeed the input capacitors play a major role on the over voltage with transients. Thank you for sharing the application note.

    This design has the input direct connected to a 12.6V battery which will keep the input capacitors charged after first cycle. Moreover, the issue seems to be happening without any change on the input voltage, since my battery is always connected.

    Vini

  • 0 in reply to Shawn Nie
    Prodigy 70 points

    Hello Shawn,

    The PG is being pulled up by a 100kohm R54. I suspect that a transient on PG is happening during the flashing of arduino, causing it to go over 6.5V thus damaging the circuit.

    The issue is not appearing anymore and we are still mitigating it.

    Thank you for your help,

    Vinicius