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TPS61185: TPS61185 Cout series resistor

tateo yamashiro
Guru 10890 points
Part Number: TPS61185

Hi,

We got a question from customer about TPS61185.
Could you help us?

[Question]
- They consider solution for mosquitone of Cout ceramic capacitors. So they will try to add series resistor on Cout.
  If they use these way, is there any concerns? Especially they have concern about phase margin.

Best Regards,
tateo

  • 0
    TI__Expert 3370 points

    Hi Tateo,

    Thanks for interesting of TPS61185! I am not sure I understand your question correctly, why does the customer want to add a series R at Cout? it will increase the output voltage ripple a lot!

    -Sheng

  • 0 in reply to Sheng Jin
    Guru 10890 points

    Thank you for your reply.
    They are considering solution for audible noise from output capacitor under the following condition.

     fpwm=120Hz
     Duty=10%

    When they used other IC, they were able to reduce audible noise by series resistor. So they want to adopt series resistor for TPS61185.
    Is there any concerns about this usage? They have concern about phase margin.

    Best Regards,
    tateo

  • 0 in reply to tateo yamashiro
    TI__Expert 3370 points

    okay, seems they want to add a damping factor to stop singing cap. I don't think it will cause a stability issue, but would recommend customer to perform a quick load transient test with THEIR BOARD, again it will increase the output ripple.did they try different sw frequency?