SC194B Datasheet, PDF (1/17 Pages) Semtech Corporation – Selectable 3.6V/3.3V/3.0V/2.5V 1A Synchronous Buck Converter

POWER MANAGEMENT
Description
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.
SC194B
Selectable 3.6V/3.3V/3.0V/2.5V
1A Synchronous Buck Converter
Features
‹ 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
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.
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
Typical Application Circuit
V_IN
3.6V to 5.5V
C_IN
10μF
SC194B
VIN
LX
EN
SYNC/PWM
VOUT
VID0
VID1
PGND
MODE
GND
L1
4.7μH
V_OUT
3.3V
1A
C_OUT
22μF
August 24, 2006
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