LMR14030-Q1: LMR14030-Q1: the overshoot of the SW waveform is too large

Sherry Liang

Part Number: LMR14030-Q1
Other Parts Discussed in Thread: LMR14030

Dear team,

My customer is using the LMR14030-Q1 in several projects, now they encountered a problem when testing as below, the overshoot of the SW waveform(marked by red circle) is too large(2.5V), their schematic is the second picture. Could you please help give me the reason why the overshoot is so large?

Thanks & Best Regards,

Sherry

over 6 years ago

0 Andy Chen over 6 years ago

TI__Mastermind 33935 points

Hi Sherry,

Did ctm test it on Diode or SW pin to GND pin? did ctm test it with shortest probe ground? can you send me PCB layout for double checking?

The Abs Max negative voltage is -3V between SW and GND per data sheet spec.

0 Sherry Liang over 6 years ago in reply to Andy Chen

TI__Genius 10255 points

Hi Andy,

thanks for your reply! I have asked ctm to do the test under your requirements, and he will send the results and the PCB layout to me next Monday.

Thanks & Best Regards,
Sherry

0 Sherry Liang over 6 years ago in reply to Andy Chen

TI__Genius 10255 points

Hi Andy,

Below is the waveform which ctm test on SW pin to GND pin with the shortest probe ground. The overshoot(marked by red) reduces but still too large.

The PCB layout is as below:

Thanks & Best Regards,

Sherry

0 Andy Chen over 6 years ago in reply to Sherry Liang

TI__Mastermind 33935 points

Hi Sherry,

The two R/C snubber are not placed close to Diode, all other external components layout are good enough.

pls remove one R/C snubber to see if any improvement on negative spike.

-1.68V(peak) negative spike is acceptable for LMR14030 operation.

0 Sherry Liang over 6 years ago in reply to Andy Chen

TI__Genius 10255 points

Hi Andy,

I will let custom try it, thank you!

Best Regards,

Sherry

Power management

Power management forum

LMR14030-Q1: LMR14030-Q1: the overshoot of the SW waveform is too large