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TPS7A63-Q1: About Cin value

Junya Kato
Expert 1635 points
Part Number: TPS7A63-Q1

Hello Team,

The recommended value of Cin in the data sheet is stated as follows.

　・Cin = 10～22uF (300mAmax)

Is it necessary to use the same Cin even when Iout=100mA(max)?
Currently, 4.7uF x 2 is used. Is there a problem?

Best regards,
Kato

  • 0
    Guru 140200 points

    Hi Kato,

    if the datasheet does not mention, that the input capacitance may be decreased if the output current is only 100mA, then I would not decrease the input capacitance. This input cap is used for the stability of the regulator. Allthough the output of a regulator looks stable, there's a fast acting control circuit in every regulator, which has to be stabilized by caps at the input and output. It's wise to follow the datasheet recommendations quite precisely. Esepecially if it is a LDO!

    What kind of input cap do you use? Is it a X7R or X5R? Take care, these caps can show a drastical decrease of capacitance when applying higher DC voltages. Do you have a datasheet of this cap?

    Kai

  • 0 in reply to kai klaas69
    TI__Expert 7015 points
    Hi Junya,

    As this is an NMOS ldo it can be very sensitive to changes in the input capacitance. I would not decrease the input capacitor with the load current as that could cause the LDO to go unstable. If you use a good X7R capacitor with less than 50% derating you should be able to use a 10uF, if your capacitor derates more than 50% I would recommend using the 22uF capacitor.

    Best Regards,
    Mark