LM2941 LDO Regulator output capacitor ESR

Robert E

Prodigy 20 points

Other Parts Discussed in Thread: LM2941

Hello,

I need a little info so I decided to join the forum and give it a shot.

To maintain a stable output the LM2941 regulator gives very specific ESR values for the 22uF+ output capacitor.

My question is, ESR at what frequency? 100kHz as listed on most cap datasheets? or some other, ripple frequency etc.

over 12 years ago

0 Donald Jones over 12 years ago

TI__Mastermind 22610 points

Technically, at some frequency that falls at least a decade below the 0dB cross-over frequency of the control loop.

In reality, stability (short of out-and-out oscillation) is a bit subjective. If you have a cap where ESR is specified only at the self-resonant frequency, or only at 100kHz, that's good enough.

0 Robert E over 12 years ago in reply to Donald Jones

Prodigy 20 points

Thank you for the quick reply.

I suppose, to be safe, I could always go with a ceramic and add in series resistance.

Then even if the ESR might quadruple from 100KHz to 10KHz the difference will be negligible, .002->.008

0 Donald Jones over 12 years ago in reply to Robert E

TI__Mastermind 22610 points

Yes, MLCC with a series R to simulate ESR is becoming preferred method when operating across the full temp range.

One caution: make sure that you have the MLCC 'capacitance vs. applied voltage' de-rating curves.

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LM2941 LDO Regulator output capacitor ESR