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About use case of Electrolytic capacitor for LP38513

Satoshi
Guru 19575 points
Other Parts Discussed in Thread: LP38513

Please let me know about output capacitor use case of Electrolytic capacitor for LP38513 below.

※Datasheet written that ceramic capacitor is recommended.

①If output capacitor using 22μF ceramic and 680μF Electrolytic, is there any risk? 

②When Electrolytic capacitor is very low ESR, is it no problem?

③If there information of recommended Cout's ESR spec, please let me know.

Best regards,

Satoshi

  • 0
    TI__Mastermind 22610 points

    Q1) If output capacitor using 22μF ceramic and 680μF Electrolytic, is there any risk?

    A1) The primary risks with a huge Cout value (680uF) are : A) reverse current through the PMOS body diode causing damage; and B) in-rush current pulling down the input supply. Secondary risk would be longer start-up times, different PSRR behavior, dynamic performance not matching any expectations set by the Typical Characteristics curves.

    Q2) When Electrolytic capacitor is very low ESR, is it no problem

    A2) No problem.

    Q3) If there information of recommended Cout's ESR spec, please let me know

    A3) General recommendations : MLCC; X5R/X7R; 10uF minimum includes de-rating for applied DC voltage, initial tolerance, and operating ambient temperature..

    Two questions for you:

       1) When you call out "... Electrolytic ...", is that Aluminum, Tantalum, or some other?

       2) Why is such a large value needed for Cout?