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TPS717: Calculating the output voltage of an LDO.

SunBae Yim
Prodigy 70 points
Part Number: TPS717

Hi,

I am trying to design an output voltage of 2.8V using TPS71701DCKR.
However, I have read through the datasheet but I don't understand your explanation.
The data sheet doesn't clearly set Vfb and I can't determine R1 and R2.

I would appreciate it if you could determine R1 and R2 for an output voltage of 2.8V.

thank you.

 

  • 0
    TI__Prodigy 60 points

    Hello, 

    I believe it says it in the datasheet on page 6 which is 0.793V. Then in the functional block diagram for adjustable on page 13 it has a .8V. That being said plugging these values into the provided equation on page 17 does not yield resistance values that agree with the table on page 18. I derived my own below.

     

  • 0 in reply to Eduardo Munoz
    TI__Mastermind 18466 points

    Hey Eduardo,

    VOUT = (1+(R1/R2))Vref

    Your equation is correct. The datasheet is incorrect and I will make a note of it so our team can correct it.

    Best,

    Juliette

  • 0 in reply to Eduardo Munoz
    Prodigy 70 points

    I knew Vfb = 0.793V. However, when I calculated it by substituting it into the formula in the data sheet, I got a completely wrong value.
    So I asked for a clear Vfb.

    In the end, it was because the formula in the data sheet was not correct.

    If I substitute Vfb into the new formula, I get the normal value.

    Thank you.