SC1403
Mobile Multi-Output PWM Controller
with Lossless Current Sense
POWER MANAGEMENT
Description
The SC1403 is a multiple-output power supply controller
designed to power battery operated systems. The
SC1403 provides synchronous buck converter control
for two (3.3V and 5V) power supplies. An efficiency of
95% can be achieved for the two supplies. The SC1403
uses Semtech’s proprietary Virtual Current Sense™ tech-
nology along with external error amplifier compensation
to achieve enhanced stability and DC accuracy over a
wide range of output filter components while maintain-
ing fixed frequency operation. Lossless current sensing
can be used to eliminate current sense resistors and
reduce cost. The SC1403 also provides a 5V linear regu-
lator for system housekeeping. The 5V linear regulator
is derived from the battery; for improved efficiency, the
output is switched to the 5V output when available.
Control functions include power-up sequencing, soft start,
power-good signaling, and frequency synchronization. Line
and load regulation is to +/-1%. The internal oscillator
can be set to 200kHz, 300kHz, 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 skip-
ping mode for high efficiency at light load, or fixed fre-
quency mode for low noise operation.
Features
3.3V and 5V dual synchronous outputs, resistor
programmable to 2.5V
Fixed frequency or PSAVE operation for maximum
efficiency over wide load range
5V / 50mA linear regulator
Virtual Current Sense™ for enhanced stability
Lossless current limiting
Out of phase switching reduces input capacitance
External compensation supports wide range of
output filter components
Programmable power-up sequence
Power Good output
Output overvoltage and overcurrent protection with
output undervoltage shutdown
6µA typical shutdown current
6mW typical quiescent power
Applications
Notebook and subnotebook computers
Tablet PCs
Embedded applications
Typical Application Circuit
Revision 5, April 2004
1
United States Patent No. 6,377,032
www.semtech.com