UCC28950 / waveform of SS pin

K.Yaita

Guru 29720 points

Other Parts Discussed in Thread: UCC28950

Hi,

My customer evaluate UCC28950 in test board, and asked about SS pin waveform (channel 2).

It seems voltage ripple about 100mV, and the ripple frequency is about 1.4Hz.

It seems that after startup of the device, the ripple is high frequency and gradually go slower.

My customer changed the device, but occured the same.

Do you have any advice about that behavior?

Regards,

Yaita

over 12 years ago

0 Mike O' over 12 years ago

TI__Guru* 86106 points

Is the test board the EVM?

0 K.Yaita over 12 years ago in reply to Mike O'

Guru 29720 points

Mike,

No, The test board is customer's board.

Please ask if you need more information(check another waveform, etc).

Regards,

Yaita

0 Mike O' over 12 years ago in reply to K.Yaita

TI__Guru* 86106 points

Hello Yaita,

I had not seen this issue on the EVM. You might want to order one and send it to the customer so he can verify it.

This issue he is having could be do to layout or just were they are probing the soft start pin. You might want to check to see if they have the scope ground connected as close to the IC ground. If it is a distance away they might just be measuring a large dv/dt in the return path caused by a large step in load.

Regards,

Mike

0 K.Yaita over 12 years ago in reply to Mike O'

Guru 29720 points

Hello Mike,

OK, I will do that.

I appreciate your support.

Yaita

Power management

Power management forum

UCC28950 / waveform of SS pin