Datasheet

+
+
PACK+
PACK-
TEMP
R
S
V
COLD
V
HOT
TS
I
NTC
bq2407x
R
P
( )
( )
H TH S
TS TH S H
V R R
Rp
I R R V
´ +
=
´ + -
2
H C
TH TC TH TC TH TC TC TH
H C TS
V V
(R + R ) (R +R ) 4 R R + (R R )
(V V ) I
Rs =
2
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bq24230
bq24232
SLUS821E –OCTOBER 2008–REVISED JANUARY 2014 www.ti.com
The allowed temperature range for a 103AT-2 type thermistor is 0°C to 50°C. However, the user can increase
the range by adding two external resistors. See Figure 31 for the circuit. The values for Rs and Rp are calculated
using the following equations:
(3)
(4)
Where:
R
TH
: Thermistor Hot Trip Value found in thermistor data sheet
R
TC
: Thermistor Cold Trip Value found in thermistor data sheet
V
H
: IC's Hot Trip Threshold = 0.3V nominal
V
C
: IC's Cold Trip Threshold = 2.1V nominal
I
TS
: IC's Output Current Bias = 75µA nominal
NTC Thermsitor Semitec 103AT-4
Rs and Rp 1% values were chosen closest to calculated values
Cold Temp Resistance and Hot Temp Resistance and Trip
External Bias Resistor, Rs (Ω) External Bias Resistor, Rp (Ω)
Trip Threshold; Ω (°C) Threshold; Ω (°C)
28000 (–0.6) 4000 (51) 0 ∞
28480 (–1) 3536 (55) 487 845000
28480 (–1) 3021 (60) 1000 549000
33890 (–5) 4026 (51) 76.8 158000
33890 (–5) 3536 (55) 576 150000
33890 (–5) 3021 (60) 1100 140000
RHOT and RCOLD are the thermistor resistance at the desired hot and cold temperatures, respectively. Note
that the temperature window cannot be tightened more than using on the thermistor connected to TS, it can only
be extended.
Figure 31. Extended TS Temperature Thresholds
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