DC-DC Converter Control Circuits
MC34063A
Design Formula Table
Calculation
Step-Up
Step-Down
Voltage-Inverting
Vout + VF - Vin(min)
Vin(min) - Vsat
Vout + VF
|Vout| + VF
Vin + Vsat
ton/toff
Vin(min) - Vsat
1
fmin
1
fmin
1
fmin
(ton/toff)max
4.0 X 10-5 ton
4.0 X 10-5 ton
4.0 X 10-5 ton
CT
ton
ton
Ipk(switch)
Rsc
2Iout(max)
+ 1
2Iout(max)
2Iout(max)
+ 1
(
)
(
)
toff
0.3 / Ipk(switch)
toff
0.3 / Ipk(switch)
0.3 / Ipk(switch)
Vin(min) - Vsat
Ipk(switch)
Vin(min)-Vsat-Vout
Vin(min) - Vsat
)
Ipk(switch)
x ton(max)
L(min)
x ton(max)
x ton(max)
(
)
(
)
(
Ipk(switch)
Iout ton
Vripple(pp)
Iout ton
Ipk(switch)(ton + toff)
8Vripple(pp)
Co
9
9
Vripple(pp)
TERMS AND DEFINITIONS
Vsat - Saturation voltage of the output switch.
VF - Forward voltage drop of the output rectifier.
The following power supply characteristics must be chosen:
Vin - Nominal input voltage.
Vout - Desired output voltage.
Iout - Desired output current.
fmin- Minimum desired output switching frequency at the selected values of Vin and IO.
Vripple(p-p) – Desired peack-to-peack 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.
May. 2009 - Rev. 1.2
HTC
− 11 −
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
