Step-Down Controllers with
Synchronous Rectifier for CPU Power
____________________________________________Application Circuits (continued)
INPUT
V+
VL
SHDN
4.7μF
BST
DH
Q1
Q2
OUTPUT
3.3V 1.8%
L1
LX
SKIP
R
SENSE
MAX797
REMOTE
SENSE
POINT
DL
PGND
CSH
CSL
FB
SS
0.01μF
R1
63.4k
0.1%
51k
5%
GND
SYNC
REF
51k
5%
R1
= VREF (1 + –––)
V
OUT
TO
VL
R2
ADJUST RANGE = 2.5V TO 4V AS SHOWN.
OMIT R2 FOR V = 2.5V.
R2
200k
0.1%
200k
5%
0.33μF
1000pF
10k
OUT
USE EXTERNAL REFERENCE
MAX495
(MAX872) FOR BETTER ACCURACY.
Figure 18. High-Accuracy Adjustable-Output Application
INPUT
4.5V TO 25V
1N4148
V+
FB
VL
BST
DH
LX
0.1μF
4.7μF
Si9410
22μF
22μF
SHDN
1N5819
-5V AT 1.5A
L1
MAX797
Si9410
CSH
CSL
150μF
150μF
0.025Ω
DL
GND
PGND
SKIP
SYNC
REF
0.33μF
L1 = DALE LPE6562-A093
Figure 19. Negative-Output (Inverting Topology) Power Supply
______________________________________________________________________________________ 29
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
