High-Efficiency, 10-Pin µMAX, Step-Down Controllers for Notebooks

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).

Applications

* 2-Way Pagers * Analog Cellular Phones * Digital Cellular Phones * Digital Still Cameras * Notebook Computers

* High Operating Frequency (300kHz)

* No Current-Sense Resistor

* Accurate Current Limit

* ±1% Total DC Error over Line and During Continuous Conduction

* Dual Mode Fixed Output

* 1.8V/2.5V/adj (MAX1762)

* 3.3V/5.0V/adj (MAX1791)

* 0.5V to 5.5V Output Adjust Range

* 5V to 20V Input Range

* Automatic Light-Load Pulse Skipping Operation

* Free-Running On-Demand PWM

* Foldback Mode™ UVLO

* PFET/NFET Synchronous Buck

* 4.65V at 25mA Linear Regulator Output

* 5µA Shutdown Supply Current

* 230µA Quiescent Supply Current

* 10-Pin µMAX Package