UCC27517A: Why do both the High-side and Low-side gate driver use the bootstrap cap and diode?

LIN YU MING

Part Number: UCC27517A
Other Parts Discussed in Thread: UCC23511, UCC23513

Hi, everyone. I use gate driver have some questions need to help. Below design often used to driving BLDC. The bootstrap Cap and diode are used to supplying the voltage to High-side MOSFET.

Why does the Low-side gate driver of the second picture use the bootstrap Cap and diode? Are there any advantage?

over 3 years ago

0 Mamadou Diallo over 3 years ago

TI__Genius 13445 points

Hello Lin,

Thanks for reaching out.

From your schematic, R32 and D11 on the low-side are not part of the bootstrap circuitry. These components accomplish 2 things:

1. R32 will protect the driver IC against large inrush current on VDD pin.

2. R32 will dampen overvoltage surges from the supply.

3. D11 will protect the supply rail against reverse currents/voltage in the event of oscillations and/or ringing at the OUT pin which will couple back to VDD through internal body diodes.

Side note: we can help you replace your optocouplers U12 and U10 with our opto-emulated gate drivers UCC23513 or UCC23511 without changes to your PCB.

Regards,

-Mamadou

0 LIN YU MING over 3 years ago in reply to Mamadou Diallo

Prodigy 80 points

Hello Mamadou,

Thank you for your reply.

Best regards,

YUMING

0 LIN YU MING over 3 years ago in reply to Mamadou Diallo

Prodigy 80 points

Hello Mamadou,

It occurred to me why everyone wasn't put R32 and D11 on the MOSFET's low-side?

Best regards,

YUMING

0 Mamadou Diallo over 3 years ago in reply to LIN YU MING

TI__Genius 13445 points

Yuming,

Did you have additional questions?

Regards,

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UCC27517A: Why do both the High-side and Low-side gate driver use the bootstrap cap and diode?