Miniature, Low-Voltage, Precision Step-Down Controller

The MAX1637 synchronous, buck, switch-mode power-supply controller generates the CPU supply voltage in battery-powered systems. The MAX1637 is a stripped-down version of the MAX1636 in a smaller 16-pin QSOP package. The MAX1637 is intended to be powered separately from the battery by an external bias supply (typically the +5V system supply) in applications where the battery exceeds 5.5V. The MAX1637 achieves excellent DC and AC output voltage accuracy. This device can operate from a low input voltage (3.15V) and delivers the excellent load-transient response needed by upcoming generations of dynamic-clock CPUs.

Using synchronous rectification, the MAX1637 achieves up to 95% efficiency. Efficiency is greater than 80% over a 1000:1 load-current range, which extends battery life in system-suspend or standby mode. Excellent dynamic response corrects output load transients caused by the latest dynamic-clock CPUs within five 300kHz clock cycles. Powerful 1A on-board gate drivers ensure fast external N-channel MOSFET switching.

The MAX1637 features a logic-controlled and synchronizable, fixed-frequency, pulse-width-modulation (PWM) operating mode. This reduces noise and RF interference in sensitive mobile-communications and pen-entry applications. Asserting the SKIP-bar pin enables fixed-frequency mode, for lowest noise under all load conditions. For a stand-alone device that includes a +5V VL linear regulator and low-dropout capabilities, refer to the MAX1636 data sheet.

Applications

* Handy-Terminals, PDAs * Notebook Computers * Subnotebook Computers

* ±2% DC Accuracy

* 0.1% (typ) DC Load Regulation

* Adjustable Switching Frequency to 350kHz

* Idle Mode™ Pulse-Skipping Operation

* 1.10V to 5.5V Adjustable Output Voltage

* 3.15V Minimum IC Supply Voltage (at VCC pin)

* Internal Digital Soft-Start

* 1.1V ±2% Reference Output

* 1µA Total Shutdown Current

* Output Overvoltage Crowbar Protection

* Output Undervoltage Shutdown (foldback)

* Tiny 16-Pin QSOP Package