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MAX1921EUT25-T Datasheet, PDF (1/11 Pages) Maxim Integrated Products – Low-Voltage, 400mA Step-Down DC-DC Converters in SOT23 | |||
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19-2296; Rev 3; 8/05
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. The
MAX1920 is also available in a 6-pin TDFN package.
Applications
Next-Generation Wireless Handsets
PDAs, Palmtops, and Handy-Terminals
Battery-Powered Equipment
CDMA Power Amplifier Supply
Typical Operating Circuit
INPUT
2V TO 5.5V
CIN
IN
LX
MAX1921
AGND
PGND
4.7µH
OUTPUT
1.5V UP TO 400mA
4.75kâ¦
5600pF
4.7µF
ON
SHDN
OUT
OFF
Features
⦠400mA Guaranteed Output Current
⦠Internal Synchronous Rectifier for >90% Efficiency
⦠Tiny 6-Pin SOT23 Package
⦠Available in 6-Pin TDFN Package (MAX1920)
⦠Up to 1.2MHz Switching Frequency for Small
External Components
⦠50µA Quiescent Supply Current
⦠0.1µA Logic-Controlled Shutdown
⦠2V to 5.5V Input Range
⦠Fixed 1.5V, 1.8V, 2.5V, 3V, and 3.3V Output
Voltages (MAX1921)
⦠Adjustable Output Voltage (MAX1920)
⦠±1.5% Initial Accuracy
⦠Soft-Start Limits Startup Current
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX1920EUT-T
MAX1920EUT+T
MAX1920ETT-T
MAX1920ETT+T
MAX1921EUT_ _-T
MAX1921EUT_ _+T
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
6 SOT23-6
6 SOT23-6
6 TDFN
6 TDFN
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.
+Denotes lead-free package.
Pin Configuration
TOP VIEW
IN 1
6 LX
65 4
MAX1920
AGND 2 MAX1921 5 PGND
MAX1920
SHDN 3
4 OUT (FB)
12 3
SOT23-6
TDFN
( ) ARE FOR MAX1920 ONLY
A "+" sign will replace the first pin indicator on lead-free packages.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maximâs website at www.maxim-ic.com.
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