General Description
The MAX1742/MAX1842 constant-off-time, pulse-width-modulated (PWM) step-down DC-DC converters are ideal for use in 5V and 3.3V to low-voltage conversion necessary in notebook and subnotebook computers. These devices feature internal synchronous rectification for high efficiency and reduced component count. They require no external Schottky diode. The internal 90mΩ PMOS power switch and 70mΩ NMOS synchronous-rectifier switch easily deliver continuous load currents up to 1A. The MAX1742/MAX1842 produce a preset 2.5V, 1.8V, or 1.5V output voltage or an adjustable output from 1.1V to VIN. They achieve efficiencies as high as 95%.

Features
♦ ±1% Output Accuracy
♦ 95% Efficiency
♦ Internal PMOS and NMOS Switches
   90mΩ On-Resistance at VIN = 4.5V
   110mΩ On-Resistance at VIN = 3V
♦ Output Voltage
   2.5V, 1.8V, or 1.5V Pin Selectable
   1.1V to VIN Adjustable
♦ 3V to 5.5V Input Voltage Range
♦ 600μA (max) Operating Supply Current
♦ <1μA Shutdown Supply Current
♦ Programmable Constant-Off-Time Operation
♦ 1MHz (max) Switching Frequency
♦ Idle-Mode Operation at Light Loads
♦ Thermal Shutdown
♦ Adjustable Soft-Start Inrush Current Limiting
♦ 100% Duty Cycle During Low-Dropout Operation
♦ Output Short-Circuit Protection
♦ 16-Pin QSOP Package

Applications
   5V or 3.3V to Low-Voltage Conversion
   CPU I/O Ring
   Chipset Supplies
   Notebook and Subnotebook Computers