TPS2117: Short circuit between IN1 and OUT

Ser

Part Number: TPS2117

Tool/software:

Hello,

Some of the pcbs we have are having the issue of short circuit between IN1 and OUT pin after assembly and simple testing of powering on the pcb.

We believe that the issue is the voltage ripple on IN1 going more than 6V during switch from IN2 to IN1. We don't see this ripple in every board. In the same board, we see it sometimes.

IN1 (5V_BUCK) is supplied through a long cable (around 1 meter), and there is only 0.1uF between the cable and the input of the mux. Also note that 5V_BUCK voltage can be as high as 5.45V by our design. So it's not simply 5.0V.

We are adding more caps on IN1 to see if it'll fix the issue. Can you also give any suggestions about this solution or any other possible solutions?

Thanks,

Blue: 5V_BUCK , purple: Vout , green: 5V_USB

3 months ago

0 Kunal Goel 3 months ago

TI__Guru* 79001 points

Hi Ser,

You can use tvs diode also on in pin and increase ceramic cap near to pin.

Regards

Kunal Goel

0 Ser 3 months ago in reply to Kunal Goel

Prodigy 70 points

Hello,

TVS diode did not help. Ceramic caps are helpful sometimes but not always.

One thing we noticed is that: Without the caps, the voltage spike happens on IN1 when OUT is between 1-2V. If the out is lower (around 0V) or higher (around 4-5V), we don't see the spike.

Any idea why would that happen?

Thanks,