2 or 3 Cell, Step-Up/Down, Two-Way Pager System IC

The MAX769 is a complete buck/boost power supply and monitoring system for two-way pagers or other low-power digital communications devices. Few external components are required. Included on-chip are:

* An 80mA output, synchronous-rectified, buck/boost DC-DC converter with a digitally controlled +1.8V to +4.9V output. The DC-DC converter is unique, since it provides a regulated output for battery inputs that are both less than and greater than the output voltage, without using transformers.

* Three low-noise linear-regulator outputs

* Three DAC-controlled comparators for software-driven, 3-channel A/D conversion

* SPI™-compatible serial interface

* Reset and low-battery (LBO) warning outputs

* Charger for NiCd/NiMH, lithium battery, or storage capacitor for RF PA power or system backup

* Two 1.8Ω (typical), serial-controlled, open-drain MOSFET switches for beeper or vibrator drive

An evaluation kit for the MAX769 (MAX769EVKIT) is available to aid in design and prototyping.Applications

* 2- or 3-Cell-Powered Handheld Equipment * GPS Receivers * Two-Way Paging

* Regulated Step-Up/Step-Down Operation

* 80mA Output from 3 Cells

* 85% Efficiency

* 13µA Idle Mode™ (coast) Current

* Selectable Low-Noise PWM or Low-Current PFM Operation

* PWM Operating Frequency Synchronized to Seven Times an External Clock Source

* Operates at 270kHz with No External Clock

* Automatic Backup-Battery Switchover