EVALUATION KIT AVAILABLE MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters General Description Features The MAX1836/MAX1837 high-efficiency step-down con- 4.5V to 24V Input Voltage Range verters provide a preset 3.3V or 5V output voltage from Preset 3.3V or 5V Output supply voltages as high as 24V. Using external feedback Adjustable Output from 1.25V to V IN resistors, the output voltage can be adjusted from 1.25V to V . An internal current-limited switching MOSFET Output Currents Up to 125mA (MAX1836) or IN 250mA (MAX1837) delivers load currents up to 125mA (MAX1836) or 250mA (MAX1837). Efficiency Over 90% The unique current-limited control scheme, operating 12A Quiescent Current with duty cycles up to 100%, minimizes the dropout volt- 3A Shutdown Current age (120mV at 100mA). Additionally, this control scheme 100% Maximum Duty Cycle for Low Dropout reduces supply current under light loads to 12A. High switching frequencies allow the use of tiny surface-mount Small 6-Pin SOT23 and TDFN Packages inductors and output capacitors. The MAX1836/MAX1837 step-down converters with inter- Ordering Information nal switching MOSFETs are available in 6-pin SOT23 PIN- TOP and 3mm x 3mm TDFN packages, making them ideal PART TEMP RANGE PACKAGE MARK for low-cost, low-power, space-sensitive applications. MAX1836ETT33-T -40C to +85C 6 TDFN-EP* AJG For increased output drive capability, use the MAX1776 step-down converter that uses an internal 24V switch to MAX1836ETT50-T -40C to +85C 6 TDFN-EP* AJE deliver up to 500mA. For even higher currents, use the MAX1836EUT33-T -40C to +85C 6 SOT23 AANY MAX1626/MAX1627 step-down controllers that drive an MAX1836EUT50-T -40C to +85C 6 SOT23 AANW external P-channel MOSFET to deliver up to 20W. MAX1837ETT33-T -40C to +85C 6 TDFN-EP* AJH Applications MAX1837ETT50-T -40C to +85C 6 TDFN-EP* AJF 9V Battery Systems MAX1837EUT33-T -40C to +85C 6 SOT23 AANZ Notebook Computers MAX1837EUT50-T -40C to +85C 6 SOT23 AANX Distributed Power Systems *EP = Exposed pad. Backup Supplies T = Tape and reel. 4mA to 20mA Loop Power Supplies Industrial Control Supplies Selector Guide appears at end of data sheet. Handheld Devices Typical Operating Circuit Pin Configurations OUTPUT INPUT TOP VIEW 3.3V OR 5V 4.5V TO 24V IN LX FB 1 6 OUT FB 1 6 OUT SHDN MAX1836 MAX1836 MAX1837 OUT GND 2 5 SHDN MAX1836 MAX1837 GND 2 5 SHDN MAX1837 IN 3 4 LX IN 3 4 LX GND FB TDFN SOT23 NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES. 19-1919 Rev 3 7/06MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Absolute Maximum Ratings IN, SHDN to GND...................................................-0.3V to +25V Operating Temperature Range..............................-40C to +85C LX to GND.......................................................-2V to (V + 0.3V) Junction Temperature.......................................................+150C IN OUT, FB to GND.......................................................-0.3V to +6V Storage Temperature Range...............................-65C to +150C Continuous Power Dissipation (T = +70C) (Note 1) Lead Temperature (soldering, 10s)...................................+300C A 6-Pin SOT23 (derate 8.7mW/C above +70C)...........696mW 6-Pin TDFN (derate 24.4mW/C above +70C).........1951mW 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. 2 Note 1: Thermal properties are specified with product mounted on PC board with 1in of copper area and still air. Electrical Characteristics (Circuits of Figures 1 (MAX1836) and 2 (MAX1837), V = 12V, SHDN = IN, T = 0C to +85C. Typical values are at T = +25C, IN A A unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Supply Range V 4.5 24 V IN V rising 3.55 4.0 4.4 IN Input Undervoltage Lockout V V UVLO Threshold V falling 3.45 3.9 4.3 IN Input Supply Current I 12 25 A IN Input Supply Current in Dropout I V = 5V 18 A IN(DROP) IN Input Shutdown Current SHDN = GND 3 7 A MAX183 EUT50, FB = GND, 4.80 5.00 5.20 MAX183 ETT50 I = 0 to 125mA LOAD Output Voltage (Preset Mode) V V OUT (MAX1836) or MAX183 EUT33, 3.168 3.30 3.432 250mA (MAX1837) MAX183 ETT33 Output Voltage Range V (Note 2) 1.25 V V OUT IN (Adjustable Mode) Feedback Set Voltage V 1.200 1.25 1.300 V FB (Adjustable Mode) OUT Bias Current V = 5V 2.5 7.4 A OUT FB Bias Current I V = 0 or 1.25V, T = +25C -25 +25 nA FB FB A TM FB Dual Mode Threshold V rising or falling 50 100 150 mV FB LX Switch Minimum Off-Time t 0.2 0.4 0.6 s OFF(MIN) LX Switch Maximum On-Time t V = 1.3V 7 10 13 s ON(MAX) FB LX Switch On-Resistance R V = 6V 1.1 2 LX IN MAX1836 250 312 450 LX Current Limit I mA LIM MAX1837 500 625 850 LX Zero-Crossing Threshold -75 +75 mV Dual Mode is a trademark of Maxim Integrated Products, Inc. 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