Analog Devices MAX1791 Product Info

• 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

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