Analog Devices MAX1761 Product Info

• Free-Running On-Demand PWM
• Selectable Light-Load Pulse-Skipping Operation
• ±1% Total DC Error in Forced-PWM Mode
• 5V to 20V Input Range
• Flexible Output Voltages
  • OUT1: Dual Mode™ Fixed 2.5V or 1V to 5.5V Adjustable
  • OUT2: Dual Mode Fixed 1.8V or 1V to 5.5V Adjustable
• Output Undervoltage Protection
• Complementary Synchronous Buck
• No Current-Sense Resistor
• 4.65V at 25mA Linear Regulator Output
• 4µA V+ Shutdown Supply Current
• 5µA VL Shutdown Supply Current
• 950µA Quiescent Supply Current
• Tiny 16-Pin QSOP Package

The MAX1761 dual pulse-width-modulation (PWM), step-down controller provides high efficiency, excellent transient response, and high DC output accuracy in an extremely compact circuit topology. These features are essential for stepping down high-voltage batteries to generate low-voltage CPU core, I/O, and chipset RAM supplies in PC board area critical applications, such as notebook computers and smart phones.

Maxim's proprietary Quick-PWM™ quick-response, constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and provides "instant-on" response to load transients while maintaining a relatively constant switching frequency.

The MAX1761 achieves high efficiency at reduced cost by eliminating the current-sense resistor found in traditional current-mode PWMs. Efficiency is further enhanced by its ability to drive large synchronous-rectifier MOSFETs. The MAX1761 employs a complementary MOSFET output stage, which reduces component count by eliminating external bootstrap capacitors and diodes.

Single-stage buck conversion allows this device 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 MAX1761 is intended for CPU core, chipset, DRAM, or other low-voltage supplies. The MAX1761 is available in a 16-pin QSOP package. For applications requiring greater output power, refer to the MAX1715 data sheet. For a single-output version, refer to the MAX1762/MAX1791 data sheet.

Applications

• 1.8V/2.5V Logic and I/O Supplies
• Digital Still Cameras
• Handy Terminals
• Notebooks and PDAs
• Smartphones