bq24010, bq24012, bq24013, bq24014
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SLUS530F − SEPTEMBER 2002 − REVISED AUGUST 2005
FUNCTIONAL DESCRIPTION
TEMPERATURE QUALIFICATION
NOTE:The
temperature qualifications apply only to versions with temperature sense input (TS) pin option (bq24010 and
bq24014).
Versions of the bqTINY with the TS pin option, continuously monitor battery temperature by measuring the voltage between
the TS and VSS pins. A negative temperature coefficient thermistor (NTC) and an external voltage divider typically
develops this voltage (see Figure 3). The bqTINY compare this voltage against the internal V
(TS1)
and V
(TS2)
thresholds
to determine if charging is allowed (see Figure 6). The temperature sensing circuit is immune to any fluctuation in V
CC
since
both the external voltage divider and the internal thresholds are ratiometric to V
CC
.
Once a temperature outside the V
(TS1)
and V
(TS2)
thresholds is detected the bqTINY immediately suspend the charge. The
bqTINY suspends charge by turning off the powerFET and holding the timer value (i.e. timers are NOT reset). Charge is
resumed when the temperature returns to the normal range.
VCC
Charge Suspend
V(TS2)
Normal Temperature Range
V(TS1)
Charge Suspend
VSS
Figure 6. TS Pin Thresholds
The resistor values of R
T1
and R
T2
are calculated by equations (1) and (2) (for NTC Thermistors )
R
T1
+
5
3
5
2
R
TH
R
TC
(9)
R
TC
*
R
TH
R
TH
R
TC
*
7
R
TC
R
TH
R
T2
+
(10)
Where R
TC
is the cold temperature resistance and R
TH
is the hot temperature resistance of thermistor, as specified
by the thermistor manufacturer.
R
T1
or R
T2
can be omitted If only one temperature (hot or cold) setting is required. Applying a constant voltage
between the V
TS1
and V
TS2
thresholds to pin TS disables the temperature-sensing feature.
11
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