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TPS7A47: Feedback-divider resistance

Atsushi Takahashi
Expert 1070 points
Part Number: TPS7A47

Hi Team,

Usage conditions: TPS7A4701, Vin=24V, Vout=22V
I'd like to lower value of Feedback-divider resistance(R1 and R2) in order to avoid Vout reduction.

1) Is it OK to R2 is 1kΩ?
*10kΩ is recommended in the data sheet but 1kΩ can keep the current through R2 over 35uA.
*R2 ≥ 1.4V/35uA = 40kΩ

2) Is there lower limit of R2?

Best Regards,

  • 0
    TI__Mastermind 45815 points

    Hi Atsushi-san,

    1. 1kΩ for R2 is no problem. Sizing the feedback resistors smaller basically just adds a small load to the LDO. Note that the inequality you mentioned is not quite correct. It should be:
      R2 ≤ 1.4V/35uA = 40kΩ
      This inequality comes from the recommendation that the current through the feedback resistors be at least 100x I_FB (100 x 350nA = 35uA) to avoid output accuracy issues. 
    2. There is no lower limit that I'm aware of. There is normally only an upper limit.

    Regards,

    Nick