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TPS62170: Feedback resistor

Julian Chen
Expert 2550 points
Part Number: TPS62170
Other Parts Discussed in Thread: TPS62172, TPS62177, TPS62125

Dear TI member,

I use TPS62170 . For some IQ issue and cusomer's demand, Feedback resistor values need to increase to RTOP=620K, RGND=200K.

Could I use this values? What do I modify the circuit?

Thanks!

  • 0
    TI__Expert 8420 points
    Hi Julian,

    Yes you can use R173=620k and R174=200k for the feedback resistor value. You can find more details in section 9.2.2.2 of the datasheet. It is recommended not to exceed 400k for the bottom resistor.

    What is the customer's Iq requirement?
  • 0 in reply to Sabrina
    Expert 2550 points
    Hi Sabrina,

    They just want to increase the feedback resistor to reduce the feedback current for lower IQ.

    They don't have any SPEC about Iq.

    Thanks!
  • 0
    TI__Guru**** 150950 points
    Hi Julian,

    This app note explains more about selecting these FB resistor values: www.ti.com/.../slyt469.pdf

    This one discusses Iq: www.ti.com/.../slyt412.pdf

    I believe you want to reduce the 'no load' input current consumption, since the Iq cannot be changed. As SLYT469 shows, the FB resistor values have a small impact on the light load efficiency--your actual system load is dominant.

    As the D/S notes, for lowest current consumption, please use the fixed 3.3Vout TPS62172 device.

    Finally, the TPS62125 and TPS62177 are similar ICs which have lower Iq. The TPS62125 is also pin to pin with TPS62170.