Rainbow Electronics MAX786 - Manual (Page 9)

MAX786
Dual-Output Power-Supply
Controller for Notebook Computers
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A synchronous rectifier at LX3 keeps efficiency high by
clamping the voltage across the rectifier diode.
Maximum current limit is set by an external low-value
sense resistor, which prevents excessive inductor cur-
rent during start-up or under short-circuit conditions. Programmable soft-start is set by an optional external
capacitor; this reduces in-rush surge currents upon
start-up and provides adjustable power-up times for
power-supply sequencing purposes.
P
+5V LDO
LINEAR
REGULATOR
V+
VL
REF
SHDN
GND
+3.3V
REFERENCE
ON
3.3V
5V
4V
2.8V
SYNC
300kHz/200kHz
OSCILLATOR ON
STANDBY
4.5V
FAULT
ON
3.3V
PWM
CONTROLLER
(SEE FIG. 3)
FB3
CS3
BST3
DH3
LX3
DL3
SS3
FB5
CS5
BST5
DH5
LX5
DL5
SS5
PGND
ON3
5V
PWM
CONTROLLER
(SEE FIG. 3)
ON
D1
D2
1.65V
1.65V
ON5
VH
Q1
Q2
Figure 2. MAX786 Block Diagram