Low-Voltage, Precision Step-Down Controller for Portable CPU Power

The MAX1636 is a synchronous, buck, switch-mode, power-supply controller that generates the CPU supply voltage in battery-powered systems. It achieves ±1% output voltage accuracy and offers the excellent load-transient response needed by upcoming generations of dynamic-clock CPUs.

Up to 95% efficiency is achieved through synchronous rectification and Maxim's proprietary Idle Mode™ control scheme. Efficiency is greater than 80% over a 1000:1 load-current range, extending battery life in system-suspend or standby modes. Excellent dynamic response corrects output load transients caused by the latest dynamic-clock CPUs within five 300kHz clock cycles. Strong, 1A, on-board gate drivers ensure fast, external N-channel MOSFET switching.

The MAX1636 features a logic-controlled and synchronizable, fixed-frequency, pulse-width-modulation (PWM) operating mode that reduces noise and RF interference in sensitive mobile communications and pen-entry applications. Holding SKIP high forces fixed-frequency mode for lowest noise under all load conditions.

For a low-cost version that omits the +5V VL linear-regulator block and comes in a smaller 16-pin QSOP package, refer to the MAX1637 data sheet.

Applications

* Bus-Termination Supplies * Computers: Desktop, Workstation, Server * Notebook Computers * Subnotebook Computers

* ±1% DC Accuracy (Adjustable Mode)

* Output Overvoltage Crowbar Protection

* Output Undervoltage Shutdown

* Adjustable Switching Frequency to 340kHz

* Low-Dropout Operation

* Idle Mode Pulse-Skipping Operation

* 1.10V to 5.5V Adjustable Output Voltage

* 2.5V/3.3V Dual-Mode Fixed-Output Settings

* Internal Digital Soft-Start

* 1.1V ±1% Reference Output

* 3µA (typ) Shutdown Current

* Open-Drain Power-Good Output (active-low RESET)

* 20-Pin SSOP Package