UNIVERSAL DC/DC CONVERTER
FSP34063
DESIGN FORMULA TABLE
Calculation
Step-Up
Step-Down
Voltage-Inverting
ton/toff
VOUT +VF
in(min) −Vsat −VOUT
VOUT +VF −V
VOUT +VF
in(min)
V
Vin(min) −Vsat
V −Vsat
in
(ton+toff)
toff
1/f
1/f
1/f
ton + toff
ton + toff
ton + toff
ton
+1
toff
ton
+1
toff
ton
+1
toff
ton
CT
(ton + toff ) −toff
4.0×10−5 ton
(ton + toff ) −toff
4.0×10−5ton
(ton + toff ) −toff
4.0×10−5ton
IPK(switch)
RSC
2Iout(max) (ton /toff +1)
0.3/ IPK (switch)
2Iout(max)
2Iout(max) (ton /toff +1)
0.3/ IPK (switch)
0.3/ IPK (switch)
L(min)
V
in(min) −Vsat
V
in(min) −Vsat −Vout
Vin(min) −Vsat
t on(max)
t on(max)
t on(max)
Ipk (switch)
Ioutton
Ipk(switch)
Ipk(switch) (toff + ton)
8Vripple( pp)
Ipk(switch)
Ioutton
Co
9
9
Vripple( pp)
Vripple( pp)
Vsat=Saturation voltage of the output switch.
VF=Forward voltage drop of the output rectifier.
The following power supply characteristics must be chosen:
Vin-Norminal input voltage
Vout-Desired output voltage, |vout|=1.25(1+ R2/R1)
Iout-Desired output current
fmin-Minimum desired output switching frequency at the selected values of Vin and Io
Vripple(pp)-Desired peak-to-peak output ripple voltage, In practice, the calculated capacitor value will need to be
increased due to its equivalent series resistance and board layout. The ripple voltage should be kept to a low value
since it will directly affect the line and load regulation.
2007-1-25
10/10
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