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www.semtech.com
SC1404
Mobile Multi-Output PWM Controller
with Virtual Current Sense
TM
POWER MANAGEMENT
Description
The SC1404 is a multiple-output power supply controller designed
to power battery operated systems. The SC1404 provides syn-
chronous rectified buck converter control for two power supplies.
An efficiency of 95% can be achieved. The SC1404 uses
Semtech’s proprietary Virtual Current Sense
TM
technology along
with external error amplifier compensation to achieve enhanced
stability and DC accuracy over a wide range of output filter compo-
nents while maintaining fixed frequency operation. The SC1404
also provides two linear regulators for system housekeeping. The
5V linear regulator takes its input from the battery; for efficiency,
the output is switched to the 5V output when available. The 12V
linear regulator output is generated from a coupled inductor off
the 5V switching regulator.
Features
6 to 30V input range (operation possible below 6V)
3.3V and 5V dual synchronous outputs
Fixed-frequency or PSAVE for maximum efficiency over
wide load current range
5V/50mA linear regulator
12V/200mA linear regulator
Virtual Current Sense
Accurate low-loss current limiting
Out-of-phase switching reduces input capacitance
External compensation supports wide range of
output filter components for reduced cost
Programmable power-up sequence
Power Good output
Output overvoltage & overcurrent protection with output
undervoltage shutdown
4μA typical shutdown current
6mW typical quiescent power
Applications
Typical Application Circuit
Control functions include: power up sequencing, soft start, power-
good signaling, and frequency synchronization. Line and load
regulation is to +/-1% of the output voltage. The internal oscilla-
tor can be adjusted to 200 kHz or 300 kHz or synchronized to an
external clock. The MOSFET drivers provide >1A peak drive cur-
rent for fast MOSFET switching.
The SC1404 includes a PSAVE# input to select pulse skipping
mode for high efficiency at light load, or fixed frequency mode for
low noise operation.
for
enhanced stability
Notebook and Subnotebook Computers
Automotive Electronics
Desktop DC-DC Converters
Revision 4, July 2003
U4
SC1404
CSH3
1
CSL3
2
COMP3
3
12OUT
4
VDD
5
S
6
ON5
7
G
8
REF
9
P
1
RESET
11
COMP5
12
CSL5
13
CSH5
14
SEQ
15
DH5
16
PHASE5
17
BST5
18
DL5
19
PGND
20
V
2
V+
22
SHDN
23
DL3
24
BST3
25
PHASE3
26
DH3
27
RUN/ON3
28
L1
+
4.7uF
10
+
+
T1
0.1uF
C7
0.1uF
0.1uF
0.1uF
3V O N /O F F
S C 1404 O N /O F F
IN P U T + 6V to + 30V
+
0.1uF
5V O N /O F F
+ 2.5V R E F
P O W E R G O O D
+ 3V O U TP U T
+ 5V A LW A Y S O N
+
4.7uF
+
2.2uF
+ 12V O U TP U T
+ 5V O U TP U T
S C 1404 O N /O F F
C11
0.22uF
0.1uF