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