AT1457
Preliminary Product Information
1-Cell Lithium-Ion And Lithium-Polymer
Charge Management IC
3. Battery Temperature Monitor
The AT1457 continuously monitors temperature by measuring the voltage between
the TS and VSS pins. A negative or a positive temperature coefficient thermistor
(NTC or PTC) and external voltage divider typically develop this voltage. The
AT1457 compares this voltage against its internal V
and V threshold to
TS1
TS2
determine if charging is allowed.
The resistor value of RT1 and RT2 ars calculated by the following equations:
For NTC Thermistor
5× RTH × RTC
RT1 =
3× (RTC − RTH )
5× RTH × RTC
RT 2
=
[(
2 × RTC
− 7 × RTH
) ( )]
For PTC Thermistor
5× RTH × RTC
3× (RTH − RTC )
5× RTH × RTC
RT1 =
RT 2
=
[
(
2 × RTH
is the cold temperature resistance and R
)
−
7 × RTC
( )]
R
is the hot temperature resistance of
TH
TC
thermistor.
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Tel: 886-3-563-0878
10/3/2006 REV:1.2
Fax: 886-3-563-0879
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