Step-Down Controllers with
Synchronous Rectifier for CPU Power
____________________________________________Application Circuits (continued)
33μF, 35V
V
(8V TO 18V AS SHOWN)
102k, 1%
IN
100k, 1%
10
2
11
+5V
AT
1N4148
4.7μF
MBR0502L
V+
SECFB
VL
14
500mA
BST
DH
T1
1:1.5
6
16
15
ON/OFF
SHDN
Q1
Q2
47μF
+3.3V
AT 2A
0.1μF
10μH
LX
25mΩ
1N5819
13
12
MAX796
Q3
DL
330μF
PGND
1N5817
102k
1%
1
8
9
SS
CSH
CSL
33.2k
1%
7
0.01μF
(OPTIONAL)
FB
SYNC
5
GND
4
REF
3
Q1-Q2 = Si9410 or EQUIVALENT
Q3 = Si9955 or EQUIVALENT (50V) PC40EEM 12.7/13.7 - A160 CORE
BEM 12.7/13.7 BOBBIN
T1 = TDK 1:1.5 TRANSFORMER
49.9k
1%
0.33μF
PRIMARY = 8 TURNS 24 AWG
SECONDARY = 12 TURNS 24 AWG
DESIGN FOR TIGHT MAGNETIC COUPLING
Figure 12. +3.3V/+5V Dual-Output Application (MAX796)
V
(9V TO 18V)
IN
22μF, 35V
107k, 1%
1000pF
221k, 1%
1μF
-5.5V OUT
(-5.5V AT 200mA)
3
11
VL
2
1N4148
22μF
10V
EQ11FS1
REF
SECFB
10
V+
DH
4.7μF
5
16
14
SYNC
1/2
Si9936
BST
0.1μF
+5V OUT
15
T1
15μH
1:1.3
(+5V AT 1A)
LX
50mΩ
220μF
1N5819
13
12
8
1/2 Si9936
MAX799
10V
DL
6
ON/OFF
PGND
SHDN
CSH
9
7
CSL
FB
GND
SS
T1 = TRANSPOWER TTI5926
4
1
0.01μF
(OPTIONAL)
Figure 13. 5V Dual-Output Application (MAX799)
26 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
