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Resistors selection for TLV1117

Eric Tian61
Intellectual 890 points

Hi,

I want to convert 3.3V to 1.8V using TLV1117-18.

Q1:

How to size R1 & R2?

(a) R1=10k, R2=4.4k

(b) R1=1k, R2=0.44k

(c) R1=0.1k, R2=0.044k

All selections above can achieve 1.8V at output, how to judge which is the best?

Q2. I have got a PCB designed as(no R1 & R2):

With input =3.3V, output is already 1.8V, are R1 and R2 not nessary?

Thanks,

Eric

  • 0
    TI__Mastermind 24975 points
    Eric,

    For the fixed output voltage version you don't need any output resistors as there are internal resistors to set the output voltage.
    You just need the input and output capacitors.

    Note that the output capacitor needs to meet a certain requirement for ESR so that the output voltage is stable. This information is in the typical applications section.

    Best,
    Michael