MAX1733/MAX1734 19-1586 Rev 0 7/00 Low-Voltage, Step-Down DC-DC Converters in SOT23 General Description Features The MAX1733/MAX1734 step-down DC-DC converters 250mA Guaranteed Output Current deliver over 250mA to outputs as low as 1.25V. These Synchronous Rectifier for Over 90% Efficiency converters use a unique proprietary current-limited con- trol scheme that achieves over 90% efficiency. These Tiny 5-Pin SOT23 Package devices maintain extremely low quiescent supply cur- 40A Quiescent Supply Current rent (40A), and their high 1.2MHz (max) operating fre- quency permits small, low-cost external components. 0.01A Logic-Controlled Shutdown This combination of features makes the MAX1733/ Up to 1.2MHz Switching Frequency MAX1734 excellent high-efficiency alternatives to linear regulators in space-constrained applications. Fixed 1.8V or 1.5V Outputs (MAX1734) Internal synchronous rectification greatly improves effi- Adjustable Output Voltage (MAX1733) ciency and eliminates the external Schottky diode required in conventional step-down converters. Both 1.5% Initial Accuracy devices also include internal digital soft-start to limit 2.7V to 5.5V Input Range input current upon startup and reduce input capacitor requirements. Soft-Start Limits Startup Current The MAX1733 provides an adjustable output voltage (1.25V to 2.0V). The MAX1734 provides factory-preset output voltages (see Selector Guide). Both are avail- Ordering Information able in space-saving 5-pin SOT23 packages. PART TEMP. RANGE PIN-PACKAGE MAX1733EUK-T -40C to +85C 5 SOT23-5 M A X17 3 4 E U K -T -40C to +85C 5 SOT23-5 Note: The MAX1734 offers two output voltages. See the Selector Applications Guide, then insert the proper designator into the blanks above to complete the part number. Cellular, PCS, and Cordless Telephones Selector Guide PDAs, Palmtops, and Handy-Terminals Battery-Powered Equipment PART V (V) TOP MARK OUT MAX1733EUK Adjustable ADKY MAX1734EUK18 1.8 ADKW MAX1734EUK15 1.5 ADKX Typical Operating Circuit Pin Configuration TOP VIEW INPUT V AT OUT 10 H +2.7V TO +5.5V 250mA IN LX IN 15 LX 2.2 F 22 F MAX1734 MAX1733 2 GND SHDN OUT MAX1734 SHDN34 OUT (FB) GND SOT23-5 ( ) ARE FOR MAX1733 ONLY. Maxim Integrated Products 1 For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.Low-Voltage, Step-Down DC-DC Converters in SOT23 ABSOLUTE MAXIMUM RATINGS IN, SHDN to GND.....................................................-0.3V to +6V Operating Temperature Range ...........................-40C to +85C Junction Temperature......................................................+150C OUT, FB, LX to GND....................................-0.3V to (V + 0.3V) IN OUT Short Circuit to GND ..........................................Continuous Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Continuous Power Dissipation (T = +70C) A 5-Pin SOT23 (derate 7.1mW/C above +70C)............571mW 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 (V = +2.7V to +5.5V, SHDN = IN, T = 0C to +85C. Typical values are at T = +25C, unless otherwise noted.) IN A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Voltage Range V 2.7 5.5 V IN Startup Voltage V 2.0 V START V rising 1.85 1.95 IN UVLO Threshold V V UVLO V falling 1.55 1.65 IN UVLO Hysteresis 200 mV No switching, no load (FB/OUT above trip Quiescent Supply Current I 40 70 A IN point) Shutdown Supply Current I SHDN = GND 0.01 4 A SHDN Output V ol ta ge R ange (MA X17 33) V 1.25 2.0 V OUT I = 0, T = +25C -1.5 +1.5 OUT A Output Voltage Accuracy % (MAX1734) I = 0 to 250mA -3 +3 OUT Load Regulation I = 0 to 250mA 0 %/mA OUT Line Regulation V = 2.7V to 5.5V 0 %/V IN OUT Sense Current (MAX1734) V = V , V = V = 5V 4 8 A OUT REG IN SHDN T = +25C, V = 3.6V 1.231 1.250 1.269 FB Feedback Threshold A IN V V FB (MAX1733) V = 3.6V 1.220 1.280 IN FB Leakage Current (MAX1733) I V = 1.5V 0.001 0.2 A FB FB SHDN Input High Voltage V 2.7V < V < 5.5V 1.6 V IH IN SHDN Input Low Voltage V 2.7V < V < 5.5V 0.4 V IL IN SHDN Leakage Current I SHDN = GND or IN 0.001 1 A SHDN High-Side Current Limit I 300 425 535 mA LIMP Low-Side Current Limit I 200 325 430 mA LIMN I = -50mA, V = 3.0V 0.7 1.4 LX IN High-Side On-Resistance R ONP I = -50mA, V = 5.5V 0.5 1.1 LX IN I = -50mA, V = 3.0V 1.0 2 LX IN Rectifier On-Resistance R ONN I = -50mA, V = 5.5V 0.8 1.6 LX IN Rectifier Off-Current Threshold I 40 mA LXOFF LX Leakage Current I V = 5.5V, V = 0 to V 0.1 5 A LXLEAK IN LX IN LX Reverse Leakage Current I IN unconnected, V = 5.5V, SHDN = GND 0.1 5 A LXLK,R LX Minimum On-Time t V = 3.6V 0.28 0.4 0.5 s ON(MIN) IN t Minimum Off-Time OFF(M IN) V = 3.6V 0.28 0.4 0.5 s IN 2 MAX1733/MAX1734