MC34063A, MC33063A, NCV33063A
8
7
6
1
S
R
Q
Q2
Q1
2
I
pk
R
0.33
sc
C
T
OSC
1N5819
3
V
in
25 V
V
CC
L
220 mH
C
+
T
100
1.25 V
Ref
Reg
+
−
Comp.
470
pF
5
4
1.0 mH
V
R2
out
5.0 V/500 mA
V
out
3.6 k
+
+
R1 1.2 k
100
470
C
O
Optional Filter
Test
Conditions
= 15 V to 25 V, I = 500 mA
Results
Line Regulation
Load Regulation
Output Ripple
V
in
V
in
V
in
V
in
V
in
V
in
12 mV = 0.12%
3.0 mV = 0.03%
120 mVpp
1.1 A
O
= 25 V, I = 50 mA to 500 mA
O
= 25 V, I = 500 mA
O
Short Circuit Current
Efficiency
= 25 V, R = 0.1 W
L
= 25 V, I = 500 mA
83.7%
O
Output Ripple With Optional Filter
= 25 V, I = 500 mA
40 mVpp
O
Figure 10. Step−Down Converter
1
2
8
7
6
1
2
V
8
7
V
out
R
R
sc
sc
V
in
V
in
6
Figure 11. External Current Boost Connections for IC Peak Greater than 1.5 A
11a. External NPN Switch 11b. External PNP Saturated Switch
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7
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