The MAX1536 constant-off-time, pulse-width-modulated (PWM) step-down DC-to-DC converter is ideal for use in +5.0V and +3.3V to low voltages for notebook and subnotebook computers. The MAX1536 features an internal PMOS power switch and internal synchronous rectification for high efficiency and reduced component count. No external Schottky diode is required across the internal synchronous rectifier switch. The internal 54mΩ PMOS power switch and 47mΩ NMOS synchronous-rectifier switch easily deliver continuous load currents up to 3.6A. The MAX1536 produces dynamically adjustable output voltages for chipsets and graphics processor cores using a logic-level control signal. The MAX1536 achieves efficiencies as high as 96%.The MAX1536 uses a unique current-mode, constant-off-time, PWM control scheme. It has selectable Idle Mode™ to maintain high efficiency during light-load operation, or fixed-PWM mode for low output ripple. The programmable constant-off-time architecture allows a wide range of switching frequencies up to 1.4MHz, optimizing performance trade-offs between efficiency, output switching noise, component size, and cost. The MAX1536 features a digital soft-start to limit surge currents during startup, a 100% duty-cycle mode for low-dropout operation, and a low-power shutdown mode that disconnects the input from the output and reduces supply current below 1µA. The MAX1536 is available in a 28-pin thin QFN package with an exposed backside pad.ApplicationsActive Termination BusesChipset/Graphics Cores with Dual-Supply VoltagesDDR Memory TerminationNotebook Computers