PMP20588: PMP20588 - Purpose of D5 and D6 and Snubber?

Phillip Karls

Part Number: PMP20588

Can anyone explain what the purpose of parts D5, D6, C20 and R21 is on the PMP20588 reference design? I have circles the components in the image below.

Thanks,

Phillip

over 4 years ago

0 Robert Taylor1 over 4 years ago

TI__Expert 6670 points

Hi Phillip,

Sorry for the very long delay here. I have asked the original designer to take a look.

That circuit is not a snubber, I believe it is used for soft start on the output.

Thanks,

Robert

+1 David Strasser over 4 years ago

TI__Intellectual 2530 points

Yes, this is a soft-start circuit to prevent output voltage over-shoot at turn-on. C20 charges slowly through R21, which slowly ramps up the feedback voltage through D5. D6 discharges C20 when the supply is turned off to reset the circuit.

Thanks,

David

0 Phillip Karls over 4 years ago in reply to David Strasser

Prodigy 80 points

Awesome, thanks for the clarification David.

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PMP20588: PMP20588 - Purpose of D5 and D6 and Snubber?