KGM34063AS
DC-TO-DC CONVERTER CONTROL CIRCUITS
Calculation
Parameter
Step-Up
(Discontinuous mode)
Vout +VF-V in(min)
Vin(min) - Vsat
Step-Down
(Continuous mode)
Vout +VF
Voltage Inverting
(Discontinuous mode)
⎢Vout ⎢+ VF
ton/toff
Vin(min) - Vsat - Vout
1/fmin
Vin - Vsat
(ton + toff)max
1/fmin
1/fmin
CT
4.5x10-5ton
4.5x10-5ton
4.5x10-5ton
IPK(switch)
RSC
CO
2Iout(max)
2Iout(max)[(ton/toff)+1]
0.3/IPK(switch)
2Iout(max)[(ton/toff)+1]
0.3/IPK(switch)
Ioutton
0.3/IPK(switch)
IPK(switch) (ton + toff)
8Vripple(p-p)
Ioutton
≡
≡
Vripple(p-p)
Vripple(p-p)
L(min)
Vin(min) - Vsat
IPK(switch)
Vin(min)-Vsat-Vout
Vin(min) - Vsat
IPK(switch)
ton(max)
ton(max)
ton(max)
IPK(switch)
NOTES:
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
V
out = Desired output voltage, ⎢Vout ⎢ = 1.25(1+R2/R1)
I
out = Desired output current
fmin = Minimum desired output switching frequency at the selected values of Vin and
lo
Vripple = Desired peak to peak output ripple voltage. In practice, the calculated
capacitor value will and 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.
Step-up With External NPN Switch
8
VOUT
1
S Q
+
Q1
R
2
7
RSC
Ipk
Oscillator
3
VIN
Comparator
6
5
1.25V
Reference
Regulator
+
-
4
6
А4
ESTEK [ Estek Electronics Co. Ltd ]
