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Minimum Duty Cycle Flag

TimothyDarling
Intellectual 2310 points

Hello Team,

I have Vin min of 5.75V and Vout of 5V at 1.3A.

When I run Switcher Pro I am getting a maximum duty cylce flag for min Vin.

The minimum duty cylce of the parts I am looking at is 90% so for the above condtions I should not get flagged since the 5/5.75 is 87%

 

  • TI__Intellectual 1280 points

    The calculations we use for duty cycle in SwitcherPro have more terms than Vo/Vin.   We use a more complicated version.

    D=(Vout+(Iout*(RdsLow+Ri)))/(Vin-(Iout*(RdsHigh-RdsLow)))

    Where

    RdsonLow is the low side resistance (FET or Diode)

    RdsonHigh is the high side resistance

    Ri is the DC resistance of the Inductor