Datasheet
HG
BOOT
I
SEN
LG
PGND
FB
V
CC
SD
PWGD
FREQ
SS
SGND
EAO
PGND
+
+
V
IN
= 5V
Vo = 1.8V@3A
100 PF
10V, 1.9A
1 x 220 PF
4V, 55 m:
2.2 PH
6.1A, 12 m:
R
fb2
R
fb1
C
c1
C
c2
R
C1
R
cs
Css
R
FADJ
R
IN
C
IN
C
c
Q1/Q2
+12V
4.99k
2.49k
2.7k
12n
43.2k
10
2.2P
0.1P
10p
560p 51.1k
C
IN1
Co1
L1
LM2742
LM2742
HG
BOOT
I
SEN
LG
PGND
FB
V
CC
SD
PWGD
FREQ
SS
SGND
EAO
PGND
+
+
V
IN
= 5V
Vo = 1.2V@10A
3 x 5600 PF
10V, 3.1A
18 m:
1.5 PH
15A, 4 m:
R
fb2
R
fb1
C
c1
C
c2
R
c1
R
CS
C
SS
R
FADJ
R
IN
C
IN
D1
C
BOOT
Q1
Q2
1.2 PH
8.2A, 6.9 m:
0.1P
1.5k
10
2.2P
88.7k
12n
270p
4.7p
229k
4.99k
4.99k
Co1-3
L
IN
L1
2 x 5600 PF
10V, 2.35A
C
IN
1,2
2x1 PF
10V
C
IN
x1, 2
LM2742
www.ti.com
SNVS266C –MARCH 2004–REVISED MARCH 2013
Figure 32. 5V to 1.2V, 10A, 300kHz
This circuit design, detailed in the Design Considerations section, uses inexpensive aluminum capacitors and off-
the-shelf inductors. It can deliver 10A at better than 85% efficiency. Large bulk capacitance on input and output
ensure stable operation.
Figure 33. 5V to 1.8V, 3A, 600kHz
The example circuit of Figure 33 has been designed for minimum component count and overall solution size. A
switching frequency of 600kHz allows the use of small input/output capacitors and a small inductor. The
availability of separate 5V and 12V supplies (such as those available from desk-top computer supplies) and the
low current further reduce component count. Using the 12V supply to power the MOSFET drivers eliminates the
bootstrap diode, D1. At low currents, smaller FETs or dual FETs are often the most efficient solutions. Here, the
Si4826DY, an asymmetric dual FET in an SO-8 package, yields 92% efficiency at a load of 2A.
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