LM3424: Buck-Boost Application current flow

Carlos Philipp

Part Number: LM3424

Hey Guys,

on page 53 in the datasheet there is an example of a buck-boost aplication. I wonder how the current flows through the LEDs.

It flows after D1 through the LED's and over Rsns back to Vin?

Is it possible to buck-boost and get the cathode of the last LED to ground?

over 2 years ago

0 Tuan Tran74 over 2 years ago

TI__Genius 17640 points

Hello Carlos,

This is a Buck Boost that is floating relative to VIN or another way to look at it is Boost to Vin. Note that the design is such that Vin can be higher or lower than the output (VLED) voltage. It's not possible to get the cathode of the last LED to ground for this design.

Thanks Tuan

0 Carlos Philipp over 2 years ago in reply to Tuan Tran74

Prodigy 30 points

Hey Tuan,

thanks for your reply!

OK I see. Instead of using Buck-Boost circuit, I could use a Sepic one?

With sepic i should be able to step down or step up with the cathod to ground?

+1 Tuan Tran74 over 2 years ago in reply to Carlos Philipp

TI__Genius 17640 points

Hi Carlos,

Yes, you can use a SEPIC for grounded cathode application.

Thanks Tuan

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LM3424: Buck-Boost Application current flow