Gate drive IC needs protection schottky diodes?

[cupoftea]

Hi,
Just bringing up a 24VIN, 24VOUT, 48Wout, 60kHz flyback.
Controller has only 5V gate drive, and weak, so used a UCC27517 gate drive IC from this
PWM controller to the NFET.

The UCC27517 gate drive IC was, I believe, ESD killed. I replaced it and now the flyback works, but the controller's
current sense pin is blown...(no doubt from the high current from when the FET was held perma-ON putting a too-high voltage across the source
sense resistors.)

Anyway, we have now got a Schottky connected from UCC27517 output to rail, and also another Schottky connected from UCC27517
output to ground (anode to ground, cathode to rail)

Do you believe this is a necessary precaution for this sensitive gate drive chip?

Gate drive ICs, often seem to get blown or ESD damaged, sensitive things they seem to be.

UCC27517
UCC27517

 

[dick_freebird]

If the failure mode is powered latchup then clamping the output against hard below-ground undershoots could be a patch. But seems you have not pinned the tail on the responsible donkey yet.

But seems you are putting Band-Aids on things based on guesswork. Some test-to-fail applying likely faults to a collection of socketed driver & controller parts until you can provoke the failure signature at will, to know why / what and then the fix.

 

[cupoftea]

Thanks, this UCC27517 was soldered on the PCB alone...then that PCB was left on the side for 3 months, and regularly handled by people, then eventually the whole board was built up...and i think the UCC27517 had gotten some ESD damage....the UCC27517 driving the two transistor forward fets (one via GDT) is fine, and that had the double schottky protection.