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TPS40200: SwitcherPro V3.17 calculates very different values for L and C than the Datasheet example P35

Part Number: TPS40200
Other Parts Discussed in Thread: SWITCHERPRO

SwitcherPro V3.17 calculates very different values for L and C than the Datasheet example P35

Vin: 18V to 52V, Vout=16V @ 1A

L1=100uH, C2 = 22uF

Datasheet P35 Example:

L1 = 220uH, C9 = 330uF

  • Hello,
    The resulting values will depend on switching frequency desired fro specific application.
    Values shown on page 35 of datasheet are calculated for switching frequency of ~200kHz (Rrc=100k, Crc=470pF). For calculation see equation 1 in datasheet.
    If you choose to operate at higher switching frequency values for L and C will be smaller.
    However in this case , care must be taken, not to violate tmin parameter values (see datasheet).
    Regards
    Brani
  • Brani,
    No matter what I input for the design,, L1 is always 100uH, C2 is always 22uF, even if I input 200kHz for Fsw
    I try differen Imax of 0.5A, 1A, 2A but those values remain the same, very different from the 330uF and 220uH of the Page 35 example

    I am trying to verify that SwitcherPro calculates close o the same values that the example has.

    Is there any other way to do this?

    Regards
  • llo,

    Im not familiar with SwitcherPro software you are using.

    For calculation purposes use application note

    www.ti.com/.../slva477b.pdf

    There is also simple spreadsheet for basic calculations for buck regulator

    buck (2).xls

    Regards

    Brani