MAX1773 Datasheet, PDF (1/20 Pages) Maxim Integrated Products – Power Source Selector for Dual-Battery Systems

19-1796; Rev 1; 1/03
EVAALVUAAILTAIOBNLEKIT
Power Source Selector for
Dual-Battery Systems
General Description
The MAX1773/MAX1773A highly integrated ICs serve
as the control logic for a system with multiple power
sources. They directly drive external P-channel
MOSFETs to select from an AC adapter and dual bat-
tery sources for charge and discharge. The selection is
made based on the presence of the power sources and
the state of the batteries. The MAX1773/MAX1773A
detect low battery conditions using integrated analog
comparators and check for the presence of a battery
by using battery thermistor outputs.
The MAX1773/MAX1773A are designed for use with a
buck topology charger. They provide a simple and easily
controlled solution to a difficult analog power control prob-
lem. The MAX1773/MAX1773A provide most of the power
source monitoring and selection, freeing the system power
management microprocessor (µP) for other tasks. This not
only simplifies development of the power management
firmware for the µP but also allows the µP to enter standby,
thereby reducing system power consumption.
The MAX1773A is recommended for new designs.
________________________Applications
Notebook and Subnotebook Computers
PDAs and Handy-Terminals
Internet Tablets
Dual-Battery Portable Equipment
Features
o Patented^† 7-MOSFET Topology Offers Low-Cost
Solution
o Automatically Detects and Responds to:
Low Battery Voltage Condition
Battery Insertion and Removal
AC Adapter Presence
o Direct Drive of P-Channel MOSFETs
o Simplifies Power Management µP Firmware
o Extends Battery Life by Allowing Power
Management µP to Enter Standby
o 4.75V to 28V AC Adapter Input Voltage Range
o Integrated LDO with 1mA Drive Capability
o Small Footprint 20-Pin TSSOP Package
Ordering Information
PART
MAX1773EUP
MAX1773AEUP
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
20 TSSOP
20 TSSOP
Pin Configuration appears at end of data sheet.
†_{Covered by U.S. Patent number 5,764,032.}
Typical Operating Circuit
AC ADAPTER
INPUT
SYSTEM LOGIC SUPPLY
FROM HOST µP
TO HOST µP
BATSEL
ACPRES
BATSTAT
ACDET
PDS
VDD
MINV
3.3V
BATTERY
A
MAX1773
MAX1773A
EXTLD
THMA
BATA
TCOMP
THMB
BATB
COMA
DISA
CHGA
COMB
DISB
CHGB
3.3V
BATTERY
B
STEP-DOWN
CHARGER
OUTPUT
INPUT
OUTPUT
3.3V DC-DC
CONVERTER
INPUT
SYSTEM LOAD
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.