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SC194B
Selectable 3.6V/3.3V/3.0V/2.5V
1A Synchronous Buck Converter
POWER MANAGEMENT
Description
August 24, 2006
Typical Application Circuit
Applications
PDA
Pocket PC and Smart Phones
USB Powered Modems
CPUs and DSPs
PC Cards and Notebooks
xDSL Applications
Standard 5-V to 3.3-V Conversion
The SC194B is a synchronous step-down converter with
integrated power devices. Four selectable output voltages
suitable for portable device interface, memory function
blocks, and 5V to 3.3V voltage conversion are available.
Automatic selection of Power Save Mode (PSAVE) is
supported which enhances ef
fi
ciency. A 100% duty cycle
mode allows operation for input voltages close to the
required output voltage.
The need for external components is minimized by
providing internal feedback compensation, and allowing
selection of the required output voltage by hard wiring VID
code inputs. The maximum current rating of the internal
MOSFET switches allows a DC output current of 1A.
The switching frequency is nominally set to 1MHz, allowing
the use of small inductors and capacitors. A
fl
exible
clocking scheme is used that allows synchronization to an
external oscillator or control by the internal oscillator.
The device can operate in either forced PWM mode or
in PSAVE mode. If PSAVE mode is enabled the part will
automatically enter PSAVE at light loads to maintain
maximum ef
fi
ciency across the full load range. For noise
sensitive applications, PSAVE mode can be disabled by
synchronizing to an external oscillator, or pulling the SYNC/
PWM pin high. Shutdown turns off all the control circuitry
to achieve a typical shutdown current of 0.1
μ
A.
Up to 95% ef
fi
ciency
PSAVE operation to maximize ef
fi
ciency
Output current — 1A
Input range — 2.7V to 5.5V
Four selectable output voltages
Quiescent current — 17
μ
A in PSAVE
Dynamic voltage positioning capability
Fixed 1MHz frequency or 750kHz to 1.25MHz syn-
chronized operation
Current mode operation for excellent line and load
transient response
100% duty cycle in dropout
Soft-start
Over-temperature and short-circuit protection
Lead-free package — 3mm x 3mm MLPD
Features
SC194B
VIN
EN
SYNC/PWM VOUT
VID0
VID1 PGND
MODE GND
LX
C
IN
L1
C
OUT
22
μ
F
10
μ
F
4.7
μ
H
V
IN
3.6V to 5.5V
V
OUT
3.3V
1A