Step-Down Controllers with
Synchronous Rectifier for CPU Power
____________________________________________Application Circuits (continued)
0.01Ω
VIN
4.75V TO 6V
L1
5μH
CSH
CSL
C1
220μF
+12V AT 2A
SYNC
D1
Q1
REF
DH
LX
MAX797
0.33μF
4.7μF
GND
SKIP
PGND
C2
C3
150μF 150μF
V+
SHDN
FB
191k
BST
VL
SS
49.9k
L1 = 2x SUMIDA CDRH125-100 IN PARALLEL
D1 = MOTOROLA MBR640
0.01μF
Q1 = MOTOROLA MTD20N03HDL
C1 = SANYO OS-CON 220μF, 10V
C2, C3 = SANYO OS-CON 150μF, 16V
Figure 16. 5V-to-12V PWM Boost Converter
INPUT
OUTPUT
+5V AT 500mA
33mΩ
CMPSH-3A
3V TO 6.5V
T1
CSH
CSL
100μF
BST
VL
220μF 220μF
Q1
DH
LX
4.7μF
MAX797
DL
Q2
PGND
HI EFF
LOW IQ
SKIP
V+
SHDN
200k
200k
FB
GND
SYNC
REF
Q1, Q2 = Si9410DY
T1 = COILTRONIX CTX 10-4
10μH PRIMARY, 1:1
0.33μF
START-UP SUPPLY VOLTAGE = 3.5V TYP
Figure 17. 90% Efficient, Low-Voltage PWM Flyback Converter (4 Cells to 5V)
28 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
