LM5181-Q1: SAMPLED FEEDBACK

Yuto Kitamura

Expert 4330 points

Part Number: LM5181-Q1

Dear team,

I have a question regarding "SAMPLED FEEDBACK" block on the functional block diagrams.

This block is positioning between comparator of Vref and FB-pin.

1. What is the function of this block?

D/S says that PSR is using "sampled valued of primary winding voltage", thus I guess it maybe doing just sample the FB values.

But if it is I have no idea how Vin is used.

2. Could you please tell me also how Vin is used?

Best regards,

Yuto

over 2 years ago

0 Marshall_Beck over 2 years ago

TI__Mastermind 30430 points

Hello Yuto,

The reflected output voltage is seen across the primary winding and the voltage seen at sw would thus be: ~Vin + Nps*Vout, so, to extract the sampled vout information, you can Vin voltage has to be involved.

0 Yuto Kitamura over 2 years ago in reply to Marshall_Beck

TI__Expert 4330 points

Hi Marshall,

Thank you for your comment.

That means "SAMPLED FEEDBACK" block is used to extract the sampled vout information.

Vin is also used to extract the reflected output from the equation, Vref ~ Vin+Nps*Vout.

Is my understanding correct?

Yuto

+1 Marshall_Beck over 2 years ago in reply to Yuto Kitamura

TI__Mastermind 30430 points

Hello Yuto, your understanding is correct.

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LM5181-Q1: SAMPLED FEEDBACK