MAX8743

19-3318; Rev 1; 8/05 MAX8743 Dual, High-Efficiency, Step-Down Controller with High Impedance in Shutdown General Description The MAX8743 is a dual pulse-width modulation (PWM) controller configured for step-down (buck) topologies that provides the high efficiency, excellent transient response, and high DC output accuracy necessary for stepping down high-voltage batteries to generate lowvoltage 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. High output impedance in shutdown eliminates negative output voltages, saving the cost of a Schottky diode at the output. 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 MAX8743 is simple and easy to compensate. Single-stage buck conversion allows the MAX8743 to directly step down high-voltage batteries for the highest possible efficiency. Alternatively, two-stage conversion (stepping down the 5V system supply instead of the battery at a higher switching frequency) allows the minimum possible physical size. The MAX8743 is intended for generating chipset, DRAM, CPU I/O, or other low-voltage supplies down to 1V. The MAX8743 is available in 28-pin QSOP and 36-pin t...