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LM317A: ESR Range for LDO Output Stability

miho komatsuda
Prodigy 10 points
Part Number: LM317A

Tool/software:

I have a question regarding the ESR of the output capacitor for the LDO. My customer is considering LM317A.

The datasheet mentions "An optional output capacitor can be added to improve transient response and can be replaced with a ceramic and appropriate ESR.",

but could you please provide the acceptable ESR range?  This information is necessary to ensure output stability.

Regards,

Komatsuda

  • 0
    TI__Expert 5150 points

    Hi Komatsuda,

    We do not have a specified or characterized acceptable ESR range for the LM317A. The frontpage description implies that one should choose an ESR value that overlaps with something that can be found in ordinary tantalum or Al electrolytic capacitors. However, since the device is stable with no output capacitors, I would expect it to work with any common ceramic value (I typically find the ESL of small package ceramics is high enough to make the impact of too-low ESR negligible everywhere in the neighborhood of the gain crossover point).

    Best,

    Gregory Thompson