MAX847 Datasheet, PDF (1/18 Pages) Maxim Integrated Products – 1-Cell, Step-Up Two-Way Pager System IC

19-1349; Rev 1a; 10/98
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1-Cell, Step-Up
Two-Way Pager System IC
________________General Description
The MAX847 is a complete power-supply and monitor-
ing system for two-way pagers or other low-power digi-
tal 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.
Pin Configuration appears at end of data sheet.
____________________________Features
o 80mA Output from 1 Cell at 90% Efficiency
o 13µA Idle Mode™ (coast) Current
o Selectable Low-Noise PWM or Low-Current
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
PART
MAX847EEI
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
28 QSOP
________________________Applications
Two-Way Pagers
GPS Receivers
1-Cell Powered Hand-Held Equipment
____________________________________________________Typical Operating Circuit
INPUT
SINGLE AA
ALKALINE BATTERY
0.8V TO 1.8V
LOW-BATTERY
IN/OUT
RESET
IN/OUT
SERIAL
I/O
1.8Ω
DRIVERS
RUN
COAST
A/D INPUT
OPTIONAL
BATT
LBI
LX1
LBO
OUT
RSIN
RSO
PGND
CS
SCL
SDI
SDO
DR1
DR2
DR2IN
DRGND
MAX847
REG2IN
OFS
REG2
REG1
RUN
REG3
CH0
SYNC _FILT
REF
AGND ^NICD
OUTPUT 2
2.85V ANALOG
OUTPUT 1
3V LOGIC
OUTPUT 3
1V RECEIVER
TO RF PA
NiCd BATTERY STACK
OR
STORAGE CAPACITOR
Idle Mode is a trademark of Maxim Integrated Products. SPI is a trademark of Motorola, Inc.
________________________________________________________________ Maxim Integrated Products 1
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