LM5069: Chip sometimes burns on startup

Joshua Feist

Part Number: LM5069

Tool/software:

Hi,

I've had a couple of these chips burn when connected to a ~55VDC source and am not sure why, as the same board works once I replace the burnt chip. I'm attaching an image of one of the burnt chips, the relevant portion of the schematic, and the layout.

3 months ago

0 Rakesh 3 months ago

TI__Guru** 102641 points

Hi Joshua,

Welcome to E2E

Are you hot-plugging 55V. ?

Can you replace C8 with 60V TVS Diode and check

Rakesh

0 Joshua Feist 3 months ago in reply to Rakesh

Prodigy 10 points

Hi,

I was hot-plugging 55V when I saw the failure. What should I check after replacing C8 with the TVS? The board seems to be working after replacing the LM5069 chip, but I'm worried about reliability, so I'd appreciate a way to confirm what was causing them to sometimes fail.

Thanks,

Joshua

+1 Rakesh 3 months ago in reply to Joshua Feist

TI__Guru** 102641 points

Hi Joshua,

The LM5069 device fails if voltage between VIN-GND or VIN-SENSE exceed the abs max voltage ratings during hot-plugging 55V. Please measure these nets close to the LM5069 pins and check.

Best Regards,

Rakesh

0 Joshua Feist 3 months ago in reply to Rakesh

Prodigy 10 points

Hi,

Thanks for your help - it looks like that was the issue, I saw transients of ~93V and will add the TVS diode.

Thanks,

Joshua

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LM5069: Chip sometimes burns on startup