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Original question:

UCC21710: UCC21710 CLAMPI pin connections for 2 parallel SiC MOSFETs (with CM choke at the gate circuit).

UCC21710: Driving 2 parallel SiC mosfet with UCC21710

Hariprasad Sunilkumar
Prodigy 20 points
Part Number: UCC21710


Hai TI team, I would like to get insight about the clamp circuit connection when driving 2 mosfets in parallel. I have read the forums and in there it is mentioned to use a pnp transistor with clamp pin and then connecting to the gate,the resistor value(10ohm) given on the clamp pin and before the transistor(100ohm) can be used for UCC21710 as well? Also, if iam using current booster, the turn on and turn off gate resistors are placed after or before the NPN-PNP transistor for the parallel connection? how is R8  choosen ? 

ucc21710e2e.jpg

Furthermore , while doing the layout, I know an isolation barrier (Clearance) is necessary between primary and secondary part of the IC but is it necessary with the DC/DC converter also? in the reference evalboard design TI has also done the same (making it a single line)but when it comes to paralleling connecting from same driver IC to 2 gate of mosfets its getting harder for layout with the isolation barrier for DC/DC converter, could you please check the image if i could break the isolation barrier for DC /DC and pour it like this ? (iam using Vincotech's internally paralleled halfbridge powermodule 30-EP232PB004ME01-PR09F07T )

 

Kind regards

Hariprasadimage.pngimage.png

  • 0
    TI__Intellectual 1016 points

    Hi Hariprasad,

    Yes, the 10-ohm resistor from the CLAMP pin helps to isolate and slow down the clamp signal so it doesn't create noise, and the 100-ohm resistor limits the base current into the transistor to avoid overloading the CLAMP pin. The resistor values should work but you should still confirm and check with how much miller current your MOSFETs generate.

    Regarding the gate resistors, the gate turn-on and turn-off resistors should be placed after the NPN-PNP transistor at each MOSFET gate. 

    Also, I can't really make out the components in your attached layout image. Can you send another one with labelled components.

    Best regards,

    Muiz