1 Cell, Step-Up Two-Way Pager System IC

The MAX847 is a complete power-supply and monitoring system for two-way pagers or other low-power digital communications devices. It requires few external components. Included on-chip are:

* A 1-cell input, 80mA output, synchronous-rectified boost DC-DC regulator with a digitally controlled +1.8V to +4.9V output

* 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

An evaluation kit for the MAX847 (MAX847EVKIT) is available to aid in design and prototyping.

Applications

* 1-Cell Powered Handheld Equipment * GPS Receivers * Two-Way Paging

* 80mA Output from 1 Cell at 90% Efficiency

* 13µA Idle Mode™ (coast) Current

* Selectable Low-Noise PWM or Low-Current Operation

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

* Operates at 270kHz with No External Clock

* Automatic Backup-Battery Switchover