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TPS62085 / Output capacitor

S.Satoshi
Guru 21685 points

Hi,

Please let me know the output capacitor selection. I know that the recommended inductor and output capacitor value is listed in Table 3, then can we use larger output capacitor than 150uF? Is there maximum limitation if we can use larger than 150uF?

Best Regards,

Sonoki / Japan Disty

  • 0
    TI__Guru**** 150950 points
    It is best to stay within the range in the D/S, but it depends on if the application allows this. Why do you want to use larger output caps? How much do you want to use?

    With larger output caps, there is a stability and startup question. Stability is generally ok with DCS-Control, but the startup can limit the total Cout allowed due to the hiccup current limit protection. But this depends on the Vout, load, etc.
  • 0 in reply to Chris Glaser
    Guru 21685 points

    Hi Chris,

    Thank you for your comment. My customer is reviewing datasheet right now and they are asking if they can use Cout larger than 150uF to improve transient response and reduce output ripple.

    I understand that the stability will not be problem but there is possibility of large inrush current at start up. Then I have following question.

    1. Does current limit protection work during startup?
    2. I think that there is possibility of startup issue due to continuous current limit working with excessive large Cout. Is my understanding correct?

    Best Regards,

    Sonoki

  • 0 in reply to S.Satoshi
    TI__Guru**** 150950 points
    Yes, current limit works during startup. And that is the risk: to trip the hiccup current limit because more Cout draws excessive current.

    I don't think Cout above 150uF helps transient response or lowers ripple. You have reached the point of diminishing returns long before this. But they can always test it and see for themselves.