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Original question:

LM1117: output capacitor type

LM1117: Stability of fixed LDO LM1117MPX-5.0

Igor Slobodnik
Prodigy 70 points
Part Number: LM1117

Hello,

I use LM117MPX-5.0 in following conditions:

- Input cap is MLCC 47uF

- Output cap is MLCC 47 uF

- Load current is 200 mA

- Vin is 6.5V

- Vout is 5V (fixed LDO)

The ESR graph for  capacitors shows ESR of about 70-80 mOhm at low frequencies, decreasing to about 5  mOhm at 100kHz.

May I consider these values to provide stability?

Thanks

  • 0
    TI__Guru 55940 points

    Hi Igor,

    ESR specifications for linear regulators are given at the resonant frequency for the capacitor. This is the lowest point on the capacitor impedance curve.

    Please be sure to check your intended capacitor specifications from the capacitor manufacturer's datasheet to ensure that they meet the ESR requirements stated in the LM1117 datasheet.  You may need to add a series resistor in order to meet the ESR specification since you are using ceramic capacitors.

    Very Respectfully,

    Ryan