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TPS65916: LDO Output Capacitors

Stephen Turner
Genius 3556 points
Part Number: TPS65916


The datasheet says in Sec. 6.2.2.5 that

"Using a 2.2-μF capacitor for each LDO output is recommended. Note, this requirement
excludes any capacitance seen at the load and only refers to the capacitance seen close to the device.
Additional capacitance placed near the load can be supported, but the end application or system should
be evaluated for stability."

 

1. How does one "evaluate for stabilty"?.

2. What happens if I put a 10uF on the LDO output?.  Will the LDO oscillate?.

thanks

  • 0
    TI__Genius 10000 points

    Stephen,

    Hi, we usually recommend measuring stability though a Bode100 or Venable machine that can measure the phase margin in a system. That said, stability is usually more of a concern for SMPS rails, than LDOs. Also, for stability, we usually worry about not enough capacitance, rather than too much. I don't see any concern with using a 10uF cap for the LDO outputs.

    Thanks,

    Nastasha

  • 0 in reply to Nastasha
    Genius 3556 points

    Hi Natasha,

    OK, so just to be clear, even though the TPS65916 datasheet says the mx capacitance on the LDO outputs is 2.7uF, you are now saying that 10uF should be OK.

    OK, we'll give it a shot and see what happens.

    thanks!

  • 0 in reply to Stephen Turner
    TI__Genius 10000 points

    Stephen,

    by going outside out maximum capacitance, we don't guarantee the performance specs of the LDO. This doesn't mean the LDO won't work. Since this is not an absolute max spec (first table of the specs in the datasheet), there is no risk of damaging the device either. We would recommend that with the higher capacitance value, you validate in your system that voltage ripple, transient, etc. meet your requirements.

    Thanks,

    Nastasha