MAX1845

19-1955; Rev 2; 1/03 KIT ATION EVALU E L B AVAILA Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit MAX1845 General Description Features o Ultra-High Efficiency o Accurate Current-Limit Option o Quick-PWM™ with 100ns Load-Step Response o 1% VOUT Accuracy over Line and Load o Dual Mode™ Fixed 1.8V/1.5V/Adj or 2.5V/Adj Outputs o Adjustable 1V to 5.5V Output Range o 2V to 28V Battery Input Range o 200/300/420/540kHz Nominal Switching Frequency o Adjustable Overvoltage Protection o 1.7ms Digital Soft-Start o Drives Large Synchronous-Rectifier FETs o Power-Good Window Comparator o 2V ±1% Reference Output The MAX1845 is a dual PWM controller configured for step-down (buck) topologies that provides high efficiency, excellent transient response, and high DC output accuracy necessary for stepping down high-voltage batteries to generate low-voltage chipset and RAM power supplies in notebook computers. The CS_ inputs can be used with low-side sense resistors to provide accurate current limits or can be connected to LX_, using low-side MOSFETs as current-sense elements. The on-demand PWM controllers are free running, constant on-time with input feed-forward. This configuration provides ultra-fast transient response, wide input-output differential range, low supply current, and tight load-regulation characteristics. The MAX1845 is simple and easy to compensate. Single-stage buck conversion allows the MAX1845 to directly step down high-voltage batteries for the hig...