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TPS717: adjustable output voltage calculation

ajayt
Genius 9555 points
Part Number: TPS717

HI Team, this does not look right section 8.2.1.2 :-   the denominator will be negative?

  • 0
    TI__Guru 55940 points
    You are correct that Equation 3 has a typo and should be R1 = R2 x ((Vout / VFB) - 1). This has been noted and will be updated in the next datasheet revision.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Genius 9555 points
    Also, I forgot to mention table 3 resistor values do not make sense on the lower voltage outputs, seem to be OK for the higher? Does Vref change for the lower voltage settings? thx
  • 0 in reply to ajayt
    TI__Guru 55940 points

    Hi ,

    Keep in mind that R2 must be within the range of ~160 k to ~320 k.  You will note that R2 for table 3 was chosen to be on the higher end of this range.  This will reduce the current flowing through the resistor divider and therefore yield better efficiency.

    If you take the recommended resistors in Table 3 and use them to calculate for Vout, you will find that they all do yield the stated output voltage.

    Vout = Vref x (1+ (R1/R2))

    Very Respectfully,

    Ryan