MAX1920 Datasheet, PDF (1/9 Pages) Maxim Integrated Products – Low-Voltage, 400mA Step-Down DC-DC Converters in SOT23

19-2296; Rev 1; 7/02
Low-Voltage, 400mA Step-Down
DC-DC Converters in SOT23
General Description
The MAX1920/MAX1921 step-down converters deliver
over 400mA to outputs as low as 1.25V. These convert-
ers use a unique proprietary current-limited control
scheme that achieves over 90% efficiency. These
devices maintain extremely low quiescent supply current
(50µA), and their high 1.2MHz (max) operating frequency
permits small, low-cost external components. This combi-
nation makes the MAX1920/MAX1921 excellent high-
efficiency alternatives to linear regulators in space-
constrained applications.
Internal synchronous rectification greatly improves effi-
ciency and eliminates the external Schottky diode
required in conventional step-down converters. Both
devices also include internal digital soft-start to limit
input current upon startup and reduce input capacitor
requirements.
The MAX1920 provides an adjustable output voltage
(1.25V to 4V). The MAX1921 provides factory-preset
output voltages (see the Selector Guide). Both are
available in space-saving 6-pin SOT23 packages.
Applications
Next-Generation Wireless Handsets
PDAs, Palmtops, and Handy-Terminals
Battery-Powered Equipment
CDMA Power Amplifier Supply
Features
o 400mA Guaranteed Output Current
o Internal Synchronous Rectifier for >90%
Efficiency
o Tiny 6-Pin SOT23 Package
o Up to 1.2MHz Switching Frequency for Small
External Components
o 50µA Quiescent Supply Current
o 0.1µA Logic-Controlled Shutdown
o 2V to 5.5V Input Range
o Fixed 1.5V, 1.8V, 2.5V, 3V, and 3.3V Output
Voltages (MAX1921)
o Adjustable Output Voltage (MAX1920)
o ±1.5% Initial Accuracy
o Soft-Start Limits Startup Current
Ordering Information
PART
MAX1920EUT-T
MAX1921EUT_ _-T
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
6 SOT23-6
6 SOT23-6
Note: The MAX1921 offers five preset output voltage options.
See the Selector Guide, and then insert the proper designator
into the blanks above to complete the part number.
Typical Operating Circuit
INPUT
2V TO 5.5V
C_IN
IN
LX
MAX1921
AGND
PGND
4.7µH
OUTPUT
1.5V UP TO 400mA
4.75kΩ
5600pF
4.7µF
ON
SHDN
OUT
OFF
Pin Configuration
TOP VIEW
IN 1
6 LX
MAX1920
AGND 2 _MAX1921 5 PGND
SHDN 3
4 OUT (FB)
SOT23-6
( ) ARE FOR MAX1920 ONLY
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