LM5141QRGEVM: A question about input capacitor

Grey Guo

Part Number: LM5141QRGEVM

C1 is the input electrolytic capacitor, why put R1=1Ω in series with C1?

Isn't this equivalent to increasing the ESR of C1 and increasing the losses?

over 2 years ago

+1 Timothy Hegarty over 2 years ago

TI__Guru* 76682 points

Hi Ray,

The inpout filter requires damping so that it doesn't affect regulator stability, the rule of thumb being Cbulk = 4*Cin_ceramic and Rdamp = SQRT(Lf/Cin_ceramic). See part 10 of this article series for more detail: http://www.how2power.com/other/EMI_Guide.php.

Regards,

Tim

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LM5141QRGEVM: A question about input capacitor