SC1403 Datasheet, PDF (1/30 Pages) Semtech Corporation – Mobile Multi-Output PWM Controller with Virtual Current SenseTM

SC1403
Mobile Multi-Output PWM Controller
with Virtual Current Sense^TM
POWER MANAGEMENT
PRELIMINARY
Description
Features
The SC1403 is a multiple-output power supply controller
designed to power battery operated systems. The
SC1403 provides synchronous rectified buck converter
control for two (3.3 V and 5 V) power supplies. An effi-
ciency of 95% can be achieved for the two supplies. The
SC1403 uses Semtech’s proprietary Virtual Current
Sense^TM technology along with external error amplifier
compensation to achieve enhanced stability and DC ac-
curacy over a wide range of output filter components
while maintaining fixed frequency operation. The SC1403
also provides a linear regulator for system housekeep-
ing. The 5 V linear regulator takes its input from the
battery; for efficiency, the output is switched to the 5V
output when available.
Control functions include: power up sequencing, soft
start, power-good signaling, and frequency synchroniza-
tion. Line and load regulation is to +/-1% of the output
voltage. The internal oscillator can be adjusted to 200
kHz or 300 kHz or synchronized to an external clock.
The MOSFET drivers provide >1A peak drive current for
fast MOSFET switching.
The SC1403 includes a PSAVE# input to select pulse
skipping mode for high efficiency at light load, or fixed
frequency mode for low noise operation.
‹ 3.3V and 5V dual synchronous outputs, resistor
programmable to 2.5V
‹ Fixed frequency or PSAVE for maximum efficiency
over wide load current range
‹ 5V / 50mA linear regulator
‹ Virtual Current Sense ^TM for enhanced stability
‹ Accurate low loss current limiting
‹ Out of phase switching reduces input capacitance
requirements
‹ External compensation supports wide range of
output filter components
‹ 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
Revision 3, August 2002
SHDN# V+ SYNC VL
4 _COMP3
COMP5 ⁵
BST3
BST5
DH3
DH5
L1
L2
PHASE3
PHASE5
DL3
DL5
PGND
CSH3
CSH5
CSL3
CSL5
FB3
FB5
SEQ
ON3
REF
ON5
PSAV#
RST#
GND
1
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