MAX1791

19-1923; Rev 0; 1/01 High-Efficiency, 10-Pin µMAX, Step-Down Controllers for Notebooks General Description The MAX1762/MAX1791 PWM step-down controllers provide high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high-voltage batteries to generate low-voltage CPU core, I/O, and chipset RAM supplies in notebook computers and PDAs. Maxim’s proprietary Quick-PWM™ pulse-width modulator is a free-running constant on-time type with input feed-forward. Its high operating frequency (300kHz) allows small external components to be utilized in PC board area-critical applications such as subnotebook computers and smart phones. PWM operation occurs at heavy loads, and automatic switchover to pulse-skipping operation occurs at lighter loads. The external high-side P-channel and low-side N-channel MOSFETs require no bootstrap components. The MAX1762/ MAX1791 are simple, easy to compensate, and do not have the noise sensitivity of conventional fixed-frequency current-mode PWMs. These devices achieve high efficiency at a reduced cost by eliminating the current-sense resistor found in traditional current-mode PWMs. Efficiency is further enhanced by their ability to drive synchronous-rectifier MOSFETs. The MAX1762/MAX1791 come in a 10-pin µMAX package and offer two fixed voltages (Dual Mode™) for each device, 1.8V/2.5V/adj (MAX1762) and 3.3V/5.0V/adj (MAX1791). o High Operating Frequency (300kHz) o No Current-Sense Resistor o Accurate Current Lim...