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limitation of minimu output voltage

Question asked by Tarzan on Sep 30, 2011
Latest reply on Oct 12, 2011 by Tarzan

In asynchronous step-down regulator, drop down of the diode has an impact on duty cycle.
Especially, we need to consider when input voltage is much higher than output voltage.

For example, ADP2300 datasheet says that
the lower limit of the output voltage is estimated by follwing fomula.

Vout(min)=Tmin-on × fsw(max) × ( Vin(max) + Vd(max)) - VD

But the value of Vf depends on If.
I'm wonder what the appropriate VD value is on this fomula because an output load current varies.

I think  it's better to set  VD as a lower voltage when we estimate limit output voltage.


What do you usually do ?


*As a reference, I've attached a datasheet of SBD which is recommended on the datasheet.
Please see fig1,2.