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LTC1479
APPLICATIONS INFORMATION
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Interfacing to the Battery Pack
The LTC1479 is designed to work with virtually any
battery pack chemistry or cell count, as long as the
battery pack operating voltage range is somewhere
between 6V and 28V. This permits great flexibility in
system design. The low-battery threshold is adjustable
and can be set anywhere between 6V and 28V.
Conventional Battery Packs
Conventional battery packs do not include a “smart”
battery interface between the battery pack and the host
system. Thus, these battery packs generally have only
three terminals to connect the battery and a temperature
sensor (thermistor) to the host system. The NTC ther-
mistor typically has a nominal resistance of 10k at room
temperature and is used to monitor the battery pack
temperature.
LOBAT and DCINGOOD Blanking/Filtering
It is good practice to include some delay in accepting low
battery and DCIN good information during transitional
periods, e.g., when switching the charger from one battery
to another or when switching from batteries to DC power.
This technique will eliminate false triggering at the asso-
ciated µP I/O. (Remember that the “3-diode” mode may be
used during periods of uncertainty to eliminate the need
for “instantaneous” DCIN and battery status information.)
Smart Battery Packs
Smart battery packs, compliant with the Smart Battery
System specification, have a five-terminal connector. Two
of the terminals are the minus and plus connections to the
battery. A third terminal is connected to the top of a
thermistor in NiCd and NiMH battery packs and to a
resistor in Li-Ion battery packs. A fourth and fifth terminal
are connected to the Smart Management Bus (SMBus)
SMBDATA and SMBCLK lines from an integrated circuit
inside the battery pack.
Applications Assistance
Linear Technology applications engineers have developed
a smart battery charger around the LT1511 charger IC.
Contact the factory for applications assistance in develop-
ing a complete smart battery system with intelligent
PowerPath control using the LTC1479.
