MC33063A
MC34063A
SLLS636L –DECEMBER 2004–REVISED DECEMBER 2009
www.ti.com
1
8
Q2
S
R
Q
Q1
2
7
6
1N5819
I
R
SC
pk
0.33 Ω
C
T
Oscillator
3
V
IN
V
CC
25 V
L
C
T
220 µH
1.25-V
Reference
Regulator
470 pF
+
+
_
100 µF
Comparator
4
5
1.0 µH
100 µF
R2
V
OUT
R2
R1
V
OUT + 1.25 (1 )
)
5 V/500 mA
3.8 kΩ
+
+
R1
1.2 kΩ
C
O
470 µF
Optional Filter
Figure 8. Step-Down Converter
TEST
CONDITIONS
VIN = 15 V to 25 V, IO = 500 mA
VIN = 25 V, IO = 50 mA to 500 mA
VIN = 25 V, IO = 500 mA
RESULTS
12 mV ± 0.12%
Line regulation
Load regulation
Output ripple
3 mV ± 0.03%
120 mVPP
1.1 A
Short-circuit current
Efficiency
VIN = 25 V, RL = 0.1 Ω
VIN = 25 V, IO = 500 mA
83.7%
Output ripple with optional filter
VIN = 25 V, IO = 500 mA
40 mVPP
1
2
8
7
1
2
8
7
V
OUT
V
OUT
R
SC
R
SC
6
V
IN
6
V
IN
a) EXTERNAL npn SWITCH
b) EXTERNAL pnp SATURATED SWITCH
Figure 9. External Current-Boost Connections for IC Peak Greater Than 1.5 A
8
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