MAX769 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – 2 or 3-Cell, Step-Up/Down, Two-Way Pager System IC

19-4771; Rev 1; 10/98
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2 or 3-Cell, Step-Up/Down,
Two-Way Pager System IC
________________General Description ____________________________Features
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 volt-
age, 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
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
Ordering Information
• Reset and low-battery (LBO) warning outputs
PART
TEMP. RANGE PIN-PACKAGE
• Charger for NiCd/NiMH, lithium battery, or storage
capacitor for RF PA power or system backup
MAX769EEI
-40°C to +85°C 28 QSOP
• 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.
Pin Configuration appears at end of data sheet.
________________________Applications
Two-Way Pagers
GPS Receivers
2 or 3-Cell Powered, Hand-Held Equipment
___________________________________________________Typical Operating Circuit
INPUT
2 OR 3 AA ALKALINE BATTERIES
1.5V TO 5.5V
LOW-BATTERY
IN/OUT
REJECT
IN/OUT
SERIAL
I/O
1.8Ω
DRIVERS
A/D
INPUT
OPTIONAL
BATT
LBI
LBO
LX1
LX2
OUT
RSIN
RSO
PGND
CS
SCL
SD1
SD03
DR1
DR2
DR2IN
DRGND
MAX769
REG2IN
OFS
REG2
REG1
CH0
REG3
SYNC
FILT
REF
AGND ^NICD
OUTPUT 2
2.85V ANALOG
OUTPUT 1
3V LOGIC
OUTPUT 3
1V RECEIVER
TO RF PA
NiCd
STORAGE
BATTERY OR _CAPACITOR
STACK
Idle Mode is a trademark of Maxim Integrated Products. SPI is a trademark of Motorola, Inc.
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