UCC21737-Q1: capacitor of SiC gate

Jay wang

Part Number: UCC21737-Q1

hi expert

when I use UCC21737-Q1 to driver SiC. According to the following information from <SLUUBX2B.pdf>. I remove a 20np capacitor in my own PCB.

BUT SiC supplier advice to add this 20np capacitor.

Pls share your valuable comments.

over 1 year ago

0 Don Dapkus over 1 year ago

TI__Guru**** 189399 points

Hi, Jay,

C26 is a simulated load for evaluation purposes. It is intended to provide a load for the driver when no power device is connected.

A small capacitor, like you have, is fine, and can help ringing on the gate.

Let us know if you have further questions, Jay.

Best regards,

Don

0 Jay wang over 1 year ago in reply to Don Dapkus

TI__Intellectual 1501 points

hi Don

whether can i think that R and C of gate both can affect ringing on the gate.

we can use large R or/and large C of gate to reduce EMI.

what is different between the two ways?

thanks.

0 Sasikala Thangam over 1 year ago in reply to Jay wang

TI__Expert 4515 points

Hi Jay,

As the timeconstant is RC, so R and C both directly proportional to rise time of the Gate voltage. But its not jsut the external Gate and external capacitance in the system, you need to consider all the R [Rint of the driver, R gate external, Rint of the FET] and C [Ciss of the FET+ external cap] of the system.

In case of higher R, we are limiting the current - but with higher C, it takes more time to charge to the required voltage.

It will be good to balance RC based on the FET's recommendation.

Here is a technote about how to choose the optimum external gate resistance.

Hope it helps.

Please press "Resolved" button if it answers your question.

Thanks

Sasi

0 Jay wang over 1 year ago in reply to Sasikala Thangam

TI__Intellectual 1501 points

thanks for your detailed answer

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UCC21737-Q1: capacitor of SiC gate