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SC194B

Selectable 3.6V/3.3V/3.0V/2.5V

1A Synchronous Buck Converter

POWER MANAGEMENT

August 24, 2006

Typical Application Circuit

Applications

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 efficiency. 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 flexible

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 efficiency 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 0.1μA.

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

Up to 95% efficiency

PSAVE operation to maximize efficiency

Output current — 1A

Input range — 2.7V to 5.5V

Four selectable output voltages

Quiescent current — 17μA 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

Description

Features

SC194B

VIN

LX

EN

SYNC/PWM

VOUT

VID0

VID1

PGND

MODE

GND

L1

22μF

10μF

4.7μH

3.6V to 5.5V

3.3V

1A