UCC21530: SiC FET Gate-Source Diodes?

stomp

Part Number: UCC21530
Other Parts Discussed in Thread: TIDA-01605, UCC21520

Hi,

We have a 3 phase inverter, built with SiC MOSFETS being driven from UCC21530 in a setup similar to TIDA-01605.

During some test cases where we had our controller's PI loop become unstable and oscillated wildly. We have randomly damaged some of the low side FET's, which always exhibit a Gate-Source short circuit.

So, somehow I feel we have exceeded a limit on the Gate of the FET, and logical assumption is to place a Schottky diode between the source and gates of the FET's.

Other customers using the same driver have diodes in their designs:

Link 1

Link 2

I am wondering if it is practical to implement a diode with the UCC21530 and can TI recommend the placement of a Gate-Source diode?

Thanks.

over 1 year ago

0 Krystian Plaskota over 1 year ago

TI__Expert 4065 points

Hi, it is practical to have this diode here, I believe you are referring to this one, Dclamp:

Also note that this is supposed to be a Zener diode.

The UCC21530 is in the same family as the UCC21520 and the same best practices are applicable to the UCC21530. You can copy the customer schematic you linked for application. As for placement, I recommend keeping the diode not too far away from the driver or the FETs to minimize the inductance of the traces, generally it's in parallel with RGS.

0 stomp over 1 year ago in reply to Krystian Plaskota

Genius 4655 points

Thanks Krystian,

Is this also applicable for when I have VSSB = -4V and VDDB + 15V as in TIDA-01605?

Thanks

+1 Krystian Plaskota over 1 year ago in reply to stomp

TI__Expert 4065 points

It wouldn't work with using a bipolar supply since the negative supply will cause the diode to conduct and will not keep the gate negative.

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UCC21530: SiC FET Gate-Source Diodes?