UCC2897A: EVM modification for 2.5V output

Barrett Bryan

Intellectual 1010 points

Part Number: UCC2897A

What modifications would I need to make to the UCC2897A-EVM to adjust output from 3.3V to 2.5V?

over 7 years ago

0 John Griffin1 over 7 years ago

TI__Mastermind 34465 points

Hello Barrett,
What you need to do is change the divider resistor R26 from 28.7k to 17.4k.
This will set the output voltage to about 2.5V

Regards
John

0 Barrett Bryan over 6 years ago in reply to John Griffin1

TI__Intellectual 1010 points

Hi John,

I think I may run into issues with synchronous rectification at a lower output voltage. Is there another similar reference design / EVM that you'd recommend for 48V to 2.5V isolated?

0 John Griffin1 over 6 years ago in reply to Barrett Bryan

TI__Mastermind 34465 points

Hi Barrett,
That's is something that you certainly need to check for. At low line the synchronous rectifier may not have enough gate voltage to turn on the FETs. If this is so and synchronous rectification is required then the transformer needs more secondary turns. The EVM will still operate because the body diodes of FETs will act as rectifier diodes but the efficiency will not be optimized.
Alternatively the FETs can be replaced with Schottky diodes.

Regards
John

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UCC2897A: EVM modification for 2.5V output