LM5116: Low Side MOSFET burns after shorting out output.

Pawel Staszewski

Part Number: LM5116

Im trying to do some tests with LM5116 (basically DC/DC buck converter 24-48V input to 12V-24V Output)

Below is schematic used - adopted from Wbench.

After connecting to 48V input DC and setting freq to 182kHz switching / and 12V output + shorting out output - low side mosfet is instantly damaged.

Currently connecting to osciloscope to check what i can catch on gate input/sw input lo and ho outputs.

Calculated by wbench to limit current to 20Amps.

0 Pawel Staszewski over 5 years ago

0 Ankit Gupta95 over 5 years ago in reply to Pawel Staszewski

Hello Pawel,

Can you please provide the scope-shot capture of the failure. That would help to debug the issue. Thanks!

Best Regards,

Ankit Gupta

Application Engineer

0 Pawel Staszewski over 5 years ago in reply to Ankit Gupta95

Thank You for reply.

It looks like all problems was caused by wrong pcb design and mistake - where top copper area was VCC_IN and bottom GND

After shorting output there is huge voltage spike like >150V DC on output and between fets (at inductor input)

Changed layout and now without mistake VCC_IN ad top copper area - and all is working no voltage "spikes" at VCC_IN and between FET's.

Paweł

0 Ankit Gupta95 over 5 years ago in reply to Pawel Staszewski

That is great news Pawel.

Can you please close this thread so that TI won't keep track of this query anymore. Thanks!

Best Regards,

Ankit Gupta

Power management forum