Mobile Multi-Output PWM Controller
with Virtual Current Sense
TM
POWER MANAGEMENT
Description
The SC1404 is a multiple-output power supply controller designed
for battery operated systems. The SC1404 provides synchronous
rectified buck converter control for two power supplies. An effi-
ciency 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 components while
maintaining fixed frequency operation. The SC1404 also pro-
vides two linear regulators for system housekeeping. The 5V lin-
ear regulator takes its input from the battery; for efficiency, the
output is switched to the 5V output when available. The 12V lin-
ear 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 current
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.
SC1404
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
TM
Virtual Current Sense 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
Revision: May 19, 2004
1
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