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Part: MAX1920EUT-T
Category:
Power Management
-> Battery Management
Description: MAX1920, MAX1921 Low-Voltage, 400mA Step-down DC-DC Converters in SOT23
Company: Maxim Integrated Products
Datasheet: Download MAX1920EUT-T datasheet File size : 649 kB
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Datasheet text preview:
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 converte r s use a unique proprietary current-limited control s c h e m e 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 combination makes the MAX1920/MAX1921 excellent highe f f i c i e n c y alternatives to linear regulators in spaceconstrained applications. Internal synchronous rectification greatly improves effic i e n c y 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 o u t p u t voltages (see the Selector Guide). Both are available in space-saving 6-pin SOT23 packages. 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
Features
MAX1920/MAX1921
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
Applications
Next-Generation Wireless Handsets PDAs, Palmtops, and Handy-Terminals Battery-Powered Equipment CDMA Power Amplifier Supply
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 IN CIN LX 4.75k 5600pF 4.7µF 4.7µH OUTPUT 1.5V UP TO 400mA
Pin Configuration
TOP VIEW
IN 1 6 LX
MAX1921
AGND PGND
AGND 2
ON SHDN OFF OUT
MAX1920 MAX1921
5
PGND
SHDN 3
4
OUT (FB)
SOT23-6
( ) ARE FOR MAX1920 ONLY
________________________________________________________________ Maxim Integrated Products
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For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Low-Voltage, 400mA Step-Down DC-DC Converters in SOT23 MAX1920/MAX1921
ABSOLUTE MAXIMUM RATINGS
IN, FB, SHDN to AGND . . . . . . . . . . . . . . . . . . . . .-0.3V to +6V OUT to AGND, LX to PGND . . . . . . . . . . . .-0.3V to (IN + 0.3V) AGND to PGND . . . . . . . . . . . . . . . . . . . . . . . . . .-0.3V to +0.3V OUT Short Circuit to GND . . . . . . . . . . . . . . . . . . . . . . . . . . .10s Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23-6 (derate 8.7mW/°C above +70°C) . . . .695mW Operating Temperature Range . . . . . . . . . . . . . .-40°C to +85°C Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . .+150°C Storage Temperature . . . . . . . . . . . . . . . . . . . .-65°C to +150°C Lead Temperature (soldering 10s) . . . . . . . . . . . . . . . . .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = 3.6V, SHDN = IN, TA = 0°C to +85°C. Typical parameters are at TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER Input Voltage Range Startup Voltage UVLO Threshold UVLO Hysteresis Quiescent Supply Current Quiescent Supply Current Dropout Shutdown Supply Current Output Voltage Accuracy (MAX1921) IOUT IIN IIN IS H D N No switching, no load SHDN = IN, OUT/FB = 0 SHDN = GND IOUT = 0, TA = +25°C IOUT = 0 to 400mA, TA = -40°C to +85°C IOUT = 0 to 200mA, TA = -40°C to +85°C OUT BIAS Current Output Voltage Range (MAX1920) FB Feedback Threshold (MAX1920) FB Feedback Hysteresis (MAX1920) FB Bias Current (MAX1920) Load Regulation Line Regulation SHDN Input Voltage High SHDN Input Voltage Low SHDN Leakage Current High-Side Current Limit VIH VIL ISHDN IL I M P SHDN = GND or IN 525 0.001 730 SHDN = 0 OUT at regulation voltage Figure 4, IN = 4.5V TA= 25°C VFB TA = -40°C to +85°C V HYS IFB FB = 1.5V IOUT = 0 to 400mA VIN = 2.5V to 5.5V 1.6 0.4 1.000 950 1.25 1.231 1.220 1.210 5 0.01 0.005 0.2 0.20 1.25 1.25 8 UVLO VIN rising VIN falling 1.50 1.85 1.65 200 50 220 0.1 -1.5 -3 -3 70 300 4.0 +1.5 +3 +3 1 16 4.00 1.269 1.280 1.280 mV µA %/mA %/V V V µA mA V µA V % SYMBOL I(LX) < 400mA VIN I(LX) < 200mA (MAX1921EUT15, MAX1921EUT18) CONDITIONS MIN 2.5 2.0 TYP MAX 5.5 2.5 2.0 1.95 V V V mV µA µA µA UNITS
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Low-Voltage, 400mA Step-Down DC-DC Converters in SOT23
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, SHDN = IN, TA = 0°C to +85°C. Typical parameters are at TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER Low-Side Current Limit High-Side On-Resistance Rectifier On-Resistance Rectifier Off-Current Threshold LX Leakage Current LX Reverse Leakage Current Minimum On-Time Minimum Off-Time SYMBOL ILIMN RO N H S RO N S R IL X O F F IL X L E A K IL X L K R tO N ( M I N ) tO F F ( M I N ) IN = SHDN = 5.5V, LX = 0 to IN IN unconnected, VLX = 5.5V, SHDN = GND 0.28 0.28 ILX = -40mA, VIN = 3V ILX = 40mA, VIN = 3V CONDITIONS MIN 350 TYP 550 0.6 0.5 60 0.1 0.1 0.4 0.4 5.0 5.0 0.5 0.5 MAX 800 1.1 0.9 UNITS mA mA µA µA µs µs
MAX1920/MAX1921
Note 1: All devices are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design.
Typical Operating Characteristics
(CIN = 2.2µF ceramic, Circuit of Figure 1, components of Table 1, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT (VOUT = 3.3V)
MAX1920 toc01
EFFICIENCY vs. LOAD CURRENT (VOUT = 2.5V)
MAX1920 toc02
EFFICIENCY vs. LOAD CURRENT (VOUT = 1.5V)
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 VIN = 5V VIN = 3.3V VIN = 2.5V
MAX1920 toc03
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.1
VIN = 3.6V VIN = 5V
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0
VIN = 2.7V
100
VIN = 4.2V
VIN = 3.3V
VIN = 5V
1
10
100
1000
0.1
1
10
100
1000
0.1
1
10
100
1000
LOAD CURRENT ( mA)
LOAD CURRENT ( mA)
LOAD CURRENT ( mA)
OUTPUT VOLTAGE ACCURACY vs. LOAD (VOUT = 3.3V)
MAX1920 toc04
OUTPUT VOLTAGE ACCURACY vs. LOAD (VOUT = 2.5V)
MAX1920 toc05
OUTPUT VOLTAGE ACCURACY vs. LOAD (VOUT = 1.5V)
MAX1920 toc06
3.399 3.366 OUTPUT VOLTAGE 3.333 3.300 VIN = 4.2V 3.267 VIN = 3.6V 3.234 3.201 0 50
2.575 2.550 OUTPUT VOLTAGE 2.525 2.500 VIN = 3V 2.475 2.450 2.425
1.545 1.530 OUTPUT VOLTAGE 1.515 1.500 1.485 1.470 1.455 VIN = 5V
VIN = 5V
VIN = 5V
VIN = 3.3V VIN = 2.5V
100 150 200 250 300 350 400 LOAD (mA)
0
50
100 150 200 250 300 350 400 LOAD (mA)
0
50
100 150 200 250 300 350 400 LOAD (mA)
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