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LM1117: Regarding input and output capacitors

Kyohei
Expert 1440 points
Part Number: LM1117

Tool/software:

Hi team,

The datasheet recommends using tantalum capacitors for input and output capacitors, but is it acceptable to use ceramic capacitors instead?

Best regards,

Kyohei

  • 0
    TI__Genius 13670 points

    Hi Kyohei,

    Input capacitors do not have an impact on the stability of the loop. We recommend that they be used as they can improve the transient performance of the LDO's. Although we recommend that a Tantalum capacitor be used, a ceramic cap may also be used at the input.

    For the output, the reason for recommending a tantalum capacitor (with relatively high ESR) is because such LDOs are internally compensated with a zero to account for the high frequency pole of the LDO's pass element.

    You can use a dummy resistor in series with the ceramic capacitor at the output. As long as you maintain the minimum amount of capacitance and ESR values specified in LM1117 datasheet which are 10uF and ESR between 0.3 - 22 Ohms in the fixed Vout version of the device and 22uF for the adjustable Vout version, the LDO will be stable. I recommend a dummy series resistor of 1 Ohm.

    Regards

    Ishaan