UCC28950 / Operation of CS pin

Ryuji

Guru 20090 points

Other Parts Discussed in Thread: UCC28950

Hello,

I have the question about CS pin operation of the UCC28950.

Please see the attached file.

3463.0841.UCC28950 CS pin voltage.pdf

UCC28950 became pulse skip mode when dynamic load resoponse.

Thus, our customer decrease the CS pin bottom resistor.

As a result, CS pin voltage became attached waveform.

Is this waveform correct ?

If there are any concern please let me know.

Best Regards,

Ryuji Asaka

over 11 years ago

0 Mike O' over 11 years ago

TI__Guru* 86286 points

Hello,

You most likely are operating in voltage mode control. If you had the controller setup in peak current mode control it would not do this. I am guessing that you have too much filtering on the CS pin. Note some customers have over filtered the CS pin believing that it is caused by noise. A little bit of jitter is normal and the cause is explained in the application note http://www.ti.com/lit/pdf/slua560 .

There is an excel design tool that goes along with this application note as well http://www.ti.com/lit/zip/sluc222.

There is an evaluation module that you can order and evaluate the topology as well. http://www.ti.com/tool/ucc28950evm-442

Regards,

Power management

Power management forum

UCC28950 / Operation of CS pin