SC1404 Datasheet, PDF (1/27 Pages) Semtech Corporation – Mobile Multi-Output PWM Controller with Virtual Current Sense

SC1404
Mobile Multi-Output PWM Controller
with Virtual Current Sense^TM
POWER MANAGEMENT
Description
Features
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.
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.
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 ^TM for enhanced stability
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
Notebook and Subnotebook Computers
Automotive Electronics
Desktop DC-DC Converters
Typical Application Circuit
IN P U T + 6V to + 30V
S C 1404 O N /O F F
10
0.22uF
S C 1404 O N /O F F
+3V O U TP U T
+
0.1uF
L1
3V O N /O F F
5V O N /O F F
0.1uF
U4
22 _V+
23 _SHDN
3 _COMP3
C7
25 _BST3
27 _DH3
26 _PHASE3
24 _DL3
SC1404
1 _CSH3
2 _CSL3
28 _RUN/ON3
7 _ON5
12OUT ⁴
VDD ⁵
COMP5 ¹²
C11
BST5 ¹⁸
0.1uF
DH5 ¹⁶
PHASE5 ¹⁷
DL5 ¹⁹
PGND ²⁰
CSH5 ¹⁴
CSL5 ¹³
SEQ ¹⁵
REF ⁹
RESET ¹¹
+5V A LW A Y S O N
0.1uF
+
4.7uF
+12V O U TP U T
+ 4.7uF
0.1uF
+
2.2uF
T1
+5V O U TP U T
+
+
0.1uF
+ 2.5V R E F
POW ER GOOD
Revision 4, July 2003
1
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