SC1403_04 Datasheet, PDF (1/31 Pages) Semtech Corporation – Mobile Multi-Output PWM Controller with Lossless Current Sense

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