UCC21750-Q1: Ucc21750 desat issue

Xinchao Liu

Part Number: UCC21750-Q1
Other Parts Discussed in Thread: UCC21750

I would like to ask a question about UCC21750Q1:

In our application, UCC21750 is used to drive SiC FET. We used the Desat function and configured the circuit as shown below, we have also done a lot of verification but we currently facing a serious problem:

the Fault signal (FLT) of UCC21750 will be pulled down to low unexpectedly and will be latched unless a reset signal is received from RST/EN ,but at the same time, we also tested the Desat signal, Vdesat, but surprisingly, Vdesat was always low and there was no sign of being triggered. we cannot understand this phenomenon, which violates the logic defined in the specification.

What is the mechanism by which the FLT of UCC21750 is pulled down? Under what circumstances will FLT signal be actively and pulled down to low ?

9 months ago

0 Andy Robles 9 months ago

TI__Genius 13650 points

Hi Xinchao,

By design the FLT pin should only go low when the voltage on the DESAT pin exceeds the thershold(9V) for longer than the de-glitch filter (140ns). We will need to further investigate what is causing the FLT signal to go low if the voltage on the DESAT-pin is not exceeding the threshold for longer than the de-glitch filter.

Questions:

What is your application?
Do you have waveforms that show FLT-pin going LOW while DESAT pin voltage remains lower than the threshold voltage (9V)?
Does the FLT-pin going LOW only happen in specific test conditions?
- I would like to understand the test conditions in which this happens to help investigate the root cause. Be as detailed as possible.
Does this issue occur in multiple drivers on the same board? Does this issue occur on the same driver location on multiple boards?
- I would like to know if this is random and happens to multiple drivers in your system or if the issue has a pattern such as it happening to the same driver location in multiple boards

Best regards,

Andy Robles

0 Xinchao Liu 9 months ago in reply to Andy Robles

Prodigy 120 points

Hello,Andy：

could you share your work email address? I can share more information that will hopefully help us analyze the problem .thank you !

0 Andy Robles 9 months ago in reply to Xinchao Liu

TI__Genius 13650 points

Hi Xinchao,

The TI field application support for Bosch has also reached out through some of our internal forums about this same issue. I will go ahead and close this thread so we can continue this investigation over email.

Best regards,

Andy Robles

0 Xinchao Liu 9 months ago in reply to Andy Robles

Prodigy 120 points

Hello,Andy:

I think you have seen my detailed description of this issue through email, but I have not received a reply from TI experts. Are there any latest analysis results?

0 Andy Robles 9 months ago in reply to Xinchao Liu

TI__Genius 13650 points

Hi Xinchao,

I have sent the latest update via email to your TI Field Application Engineering support. Let's continue this conversation via email.

Best regards,

Andy Robles

0 Xinchao Liu 9 months ago in reply to Andy Robles

Prodigy 120 points

Dear,Andy:

Could you share the email to my email ,FAE has not responded to any messages since last week.

0 Xinchao Liu 9 months ago in reply to Andy Robles

Prodigy 120 points

Hello,Andy:

0 Andy Robles 9 months ago in reply to Xinchao Liu

TI__Genius 13650 points

Hi Xinchao,

FAE has booked a meeting for us to talk about the issue in a couple hours. Looking forward to talking with you.

Best regards,

Andy Robles

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UCC21750-Q1: Ucc21750 desat issue