LM5022: LM5022 in SEPIC, IC fails, runs hot

Joseph St. Amour

Part Number: LM5022

I have an LM5022 in SEPIC configuration, that I can vary from 5-35VDC. Maximum continuous current is about 1.5A, and pulsed current is as high as 5A for short durations. The output is connected to an LED current source circuit to drive power LEDs.

Problem I have is that occasionally (about 1 out of every 10 or so) assemblies, the LM5022 appears to fail immediately (upon power up, or when the load is first connected). The LM5022 body will become very hot and draw large amounts of current. Replacing it generally will fix the issue.

I am not sure what could be causing this intermittent issue and I have not been able to replicate when or how this fault occurs.

over 3 years ago

0 Joseph St. Amour over 3 years ago

Prodigy 180 points

1832.Driver.pdf

Circuit diagram attached

0 Stefan Schauer over 3 years ago in reply to Joseph St. Amour

TI__Guru 58641 points

Hi Joseph,

thank you for using the E2E forum.

To ensure we investigate on the right side, it would be good to check a few things first.

Have you already checked the soldering on the failing boards?

Have you tried to swap the device on a failing and a passing board? - Does the issue stick with the device?

Best regards,

Stefan

0 Joseph St. Amour over 3 years ago in reply to Stefan Schauer

Prodigy 180 points

Stefan
Thanks for the input. Upon closer inspection, I found the sense resistor (R6) and MOSFET (Q1) are damaged. The resistor is browned and shows some surface damage and the MOSFET appears to have shorted across D-S. The surrounding connected copper is darkened, so it's clear that there was a very high current draw event that heated these components up significantly.

Board solder quality is good.

0 Stefan Schauer over 3 years ago in reply to Joseph St. Amour

TI__Guru 58641 points

Hi Joseph,

thank you for the info. So I will close this thread.

If you have any additional Question, just reply to reopen this thread or start a new one for another topic.

Best regards,

Stefan

Power management

Power management forum

LM5022: LM5022 in SEPIC, IC fails, runs hot