MAX1776 19-1975 Rev 2 7/03 24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter General Description Features The MAX1776 high-efficiency step-down converter pro- Fixed 5V or Adjustable Output vides an adjustable output voltage from 1.25V to V from IN 4.5V to 24V Input Voltage Range supply voltages as high as 24V. An internal current-limit- ed 0.4 MOSFET delivers load currents up to 600mA. Up to 600mA Output Current Operation to 100% duty cycle minimizes dropout volt- Internal 0.4 P-Channel MOSFET age (240mV at 600mA). Efficiency Over 95% The MAX1776 has a low 15A quiescent current to improve light-load efficiency and conserve battery life. 15A Quiescent Supply Current The device draws only 3A while in shutdown. 3A Shutdown Current High switching frequencies (up to 200kHz) allow the use of tiny surface-mount inductors and output capaci- 100% Maximum Duty Cycle for Low Dropout tors. The MAX1776 is available in an 8-pin MAX pack- Current-Limited Architecture age, which uses half the space of an 8-pin SO. For increased output drive capability, use the MAX1626/ Thermal Shutdown MAX1627 step-down controllers, which drive an exter- Small 8-MAX Package nal P-channel MOSFET to deliver up to 20W. Applications Ordering Information Notebook Computers PART TEMP RANGE PIN-PACKAGE Distributed Power Systems MAX1776EUA -40C to +85C 8 MAX Keep-Alive Supplies Hand-Held Devices Typical Operating Circuit Pin Configuration TOP VIEW V IN SHDN IN ILIM LX V FB 1 8 OUT OUT GND 2 7 SHDN MAX1776 MAX1776EUA ILIM 3 6 ILIM2 ILIM2 OUT LX 4 5 IN MAX FB GND MAX Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.24V, 600mA Internal Switch, 100% Duty Cycle, Step-Down Converter ABSOLUTE MAXIMUM RATINGS IN, SHDN, ILIM, ILIM2 to GND .................................-0.3V to 25V Continuous Power Dissipation (T = +70C) A LX to GND.......................................................-2V to (V + 0.3V) 8-Pin MAX (derate 4.1mW/C above +70C) .............330mW IN OUT, FB to GND .........................................................-0.3V to 6V Operating Temperature Range ...........................-40C to +85C Peak Input Current .................................................................. 2A Junction Temperature......................................................+150C Maximum DC Input Current.............................................. 500mA Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C 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 (Circuit of Figure 1, V = +12V, SHDN = IN, T = 0C to +85C, unless otherwise noted.) IN A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Voltage Range V 4.5 24 V IN Input Supply Current I No load 15 28 A IN Input Supply Current in Dropout I No load 50 70 A IN(DROP) Input Shutdown Current SHDN = GND 3 7 A V rising 3.6 4.0 4.4 IN Input Undervoltage Lockout V V UVLO Threshold V falling 3.5 3.9 4.3 IN Output Voltage (Preset Mode) V FB = GND 4.80 5.00 5.20 V OUT Feedback Set Voltage V 1.212 1.25 1.288 V FB (Adjustable Mode) OUT Bias Current V = 5.5V 1.65 3.5 6.25 A OUT OUT Pin Maximum Voltage 5.5 V FB Bias Current I V = 1.3V -25 +25 nA FB FB FB Dual Mode Threshold Low 50 100 150 mV LX Switch Minimum Off-Time t 0.22 0.42 0.62 s OFF(MIN) LX Switch Maximum On-Time t V = 1.3V 8 10 12 s ON(MAX) FB ILIM = ILIM2 = GND 1.6 3.2 ILIM = GND, ILIM2 = IN 0.8 1.6 V = 6V IN ILIM = IN, ILIM2 = GND 0.4 0.8 ILIM = ILIM2 = IN 0.4 0.8 LX Switch On-Resistance R LX ILIM = ILIM2 = GND 1.9 3.8 ILIM = GND, ILIM2 = IN 1.0 1.9 V = 4.5V IN ILIM = IN, ILIM2 = GND 0.5 0.95 ILIM = ILIM2 = IN 0.5 0.95 ILIM = ILIM2 = GND 120 150 180 ILIM = GND, ILIM2 = IN 240 300 360 LX Current Limit I mA LX(PEAK) ILIM = IN, ILIM2 = GND 480 600 720 ILIM = ILIM2 = IN 960 1200 1440 LX Zero-Crossing Threshold -75 +75 mV Zero-Crossing Timeout LX does not rise above the threshold 30 s T = +25C1 V = 24V, A IN LX Switch Leakage Current A LX = GND T = 0C to +85C10 A Dual Mode is a trademark of Maxim Integrated Products, Inc. 2 MAX1776