MAX769

19-4771; Rev 1; 10/98 ANUAL N KIT M EET IO T A U EVAL TA SH WS DA FOLLO 2 or 3-Cell, Step-Up/Down, Two-Way Pager System IC ____________________________Features o Regulated Step-Up/Step-Down Operation o 80mA Output from 3 Cells o 85% Efficiency o 13µA Idle Mode™ (coast) Current o Selectable Low-Noise PWM or Low-Current PFM Operation o PWM Operating Frequency Synchronized to Seven Times an External Clock Source o Operates at 270kHz with No External Clock o Automatic Backup-Battery Switchover ________________General Description The MAX769 is a complete buck/boost power supply and monitoring system for two-way pagers or other lowpower 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 softwaredriven, 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 1.8 Ω (typical), serial-controlled, open-drain MOSFET switches for beeper or vibrator drive An evaluation kit for the MAX769 (MAX769EVKIT) is available to aid in des...