Datasheet

HG
BOOT
ISEN
LG
PGND
FB
Vcc
SD
PWGD
FREQ
SS
SGND
EAO
PGND
+
+
+5V
Vin = 3.3V
Vo = 0.8V@5A
1 x 5600 uF
10V, 2.35A
2 x 4700 uF
16V, 2.8A
1 uH
11 A, 3.7 m:
Rfb2
Rfb1
Cc1
Cc2
Rc1
Rcs
Css
Rfadj
Rin
Cin
D1
Cboot
Q1
Q2
1uF
10V
1 uH
4.5 A, 7.5 m:
4.99k
3.3k
14.9k
147k
4.7p
680p
12n
49.9k
2.2u
10
0.1u
Co1,2
Cin1
Cinx
Lin
L1
LM27x7
HG
BOOT
ISEN
LG
PGND
FB
Vcc
SD
PWGD
FREQ
SS
SGND
EAO
PGND
+
+
Vin = 5V
Vo = 1.8V@3A
100 uF
10V, 1.9A
1 x 220 uF
4V, 55 m:
2.2 uH
6.1A, 12 m:
Rfb2
Rfb1
Cc1
Cc2 Rc1
Rcs
Css
Rfadj
Rin
Cin
Cc
Q1/Q2
+12V
4.99k
2.49k
2.7k
12n
43.2k
10
2.2u
0.1u
10p
560p 51.1k
Cin1
Co1
L1
LM27x7
LM2727, LM2737
www.ti.com SNVS205D –AUGUST 2002–REVISED MARCH 2013
Figure 27. 5V to 1.8V, 3A, 600kHz
The example circuit of Figure 27 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.
Figure 28. 3.3V to 0.8V, 5A, 500kHz
The circuit of Figure 28 demonstrates the LM2727 delivering a low output voltage at high efficiency (87%) A
separate 5V supply is required to run the chip, however the input voltage can be as low as 2.2
Copyright © 2002–2013, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Links: LM2727 LM2737