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TPS62801: output cap range

Part Number: TPS62801

The TPS62801 datasheet states an effective output capacitance of up to 26uF.  Is this referring to the nominal value of the output cap or should I be derating the output cap for DC Bias and other similar effects first?

Also, what if I have other bulk caps (or other devices) in my design connected to this voltage?  Do I need to include these when determining if I am less than 26uF or is it only the output cap(s) that are physically close to the power supply IC?

Regards,

Matt

  • Hi Matt,

    Yes, effective means the real, actual capacitance present. This is lower than the nominal (in most cases, with DC bias).

    All caps on the output net of the PCB are 'seen' by the device. The IC can't tell which page of your schematic the caps are on.

    I'm very curious why you would have so much output cap with such a small, fast device? Why do you use so much?
  • The amount of output cap was based from a previous design that was using a much slower power supply.  So it appears with this new power supply I can reduce the capacitance.  Just for my own understanding, is the limit on capacitance to ensure stability of the power supply or is it for some other reason?

    -Matt

  • Thanks for confirming. Yes, most newer supplies are faster and this requires less capacitance.

    The main limit on the maximum capacitance is indeed stability.