UCC28950 / Working Error Problem

Kuramochi Tadahiko

Guru 28715 points

Other Parts Discussed in Thread: UCC29950

Hi,

Following wrong waveforms are observed on the my customer's circuit.

Followings are another information;

- Frequency of this error working is increase as load power.

And it also depends on the resistor during TMIN pin and GND.

Frequency increases the more the resistance is large.

- Waveform of OUTA/B is correct.

Could you tell me the reason of this error working and corresponding?

Please send me the e-mail if you need their circuit.

kuramochi@fujiele.co.jp

Best Regards,

Kuramochi

over 8 years ago

0 Brian Johnson96 over 8 years ago

TI__Expert 3200 points

Hi Kuramochi,

I will forward your question to an AE.

0 Colin Gillmor over 8 years ago in reply to Brian Johnson96

TI__Mastermind 25570 points

Hello Kuramochi-san

You are correct that there is a similar issue at DMAX when the UCC29950 is operating at current limit. In your case the system seems to be operating at Dmax but not at the current limit point and I think the problem is due to noise coupled onto the CS pin during switching which terminates the 'missing' cycle immediately it starts.

Could you send me the PCB Gerber files and I'll review them to see if there are any things we could suggest to help diagnose and solve this issue ? You can send them to me directly at colingillmor@ti.com - they will of course be treated as confidential information and won't be shared.

BTW

Is this the same issue as the one at https://e2e.ti.com/support/power_management/isolated_controllers/f/188/p/558338/2048463#2048463 ?

Regards
Colin

Power management

Power management forum

UCC28950 / Working Error Problem