UCC28780: UCC28780 PWMH issue

Hi Lawrence,

Thanks for your interest in UCC28780. May I ask how are you probing the PWMH pin? From the waveforms you shared, it looks like switching noise is coupling onto the PWMH probe. Have you tried using a tip and barrel probe to measure PWMH?

Best Regards,
Ben Lough

Hi, Ben

our client was fixed issue QR mode was can work.

but we find the switching noise affect  high side GaNFET active abnormal , result in high low side FET active in the meantime , and triger OCP.

If any suggestion, Please advise me.

Thanks,

Best regards,

Lawrence.

Hi Lawrence,

I understood your statement to be the high side and low side FETs occasionally turn on at the same time due to noise. Is this what you are seeing? How are you probing PWMH?

Best Regards,

Ben Lough

Hi, Ben

 

This issue happened at only when start up and the first PWM of burst mode.

 

At these condition below, device work well:

1. Work in active clamp mode

2. After removed buffer IC

 

The gate signal can’t be measured due to high low side shorted while probe touched (GND is shortest loop)

But we can measure the gate signal before buffer IC, it’s normal.

 

Could you please advise that what signal we should measure for your reference, thank you.

 

Best regards,

 

Lawrence.