LM27402: Problem with adding constant current limit

Eching Cheung

Prodigy 10 points

Part Number: LM27402

Hi Team,

I have some LM27402 module on hand, which works well on 12V input and 5V output up to 20A.

Here is the module circuit

Here is the module circuit.

I am trying to add a CV/CC function to limit the output within 0.6-5V, 0-10A.

Here is the new circuit with opamp added.

However, the module get oscillation if opamp output connected to FB pin. How could I solve this problem?

Thank you all.

over 1 year ago

0 Athos Zhao over 1 year ago

TI__Expert 7320 points

Hi Eching,

Our US team will reply you next Monday.

+1 David_Daniels over 1 year ago

TI__Mastermind 21665 points

Based on your description of an issue with the addition the op amp circuit, it seems the CC loop is interacting with the CV loop. Typically, the loop bandwidths are significantly apart to minimize the interaction between the cc and cv loops. An addition of an 10uF capacitor from pin 4 to pin 1 of the opamp will add a pole to the loop and slow the cc loop down and should improve the performance.

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LM27402: Problem with adding constant current limit