BQ24105-Q1 Datasheet, PDF (23/35 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH INTEGRATED POWER FETs ( bqSWITCHER™)

bq24105-Q1
www.ti.com................................................................................................................................................................................................. SLUS953 – AUGUST 2009
6. Determine TTC capacitor (_TTC) for the 5.0 hours safety timer using the following equation:
C_TTC
+
t_CHARGE
K_TTC
C_TTC
+
300 m
2.6 mńnF
C_TTC + 115.4 nF
(22)
Select standard value 100 nF, 16V, X7R, ±10% ceramic capacitor (i.e., Panasonic ECJ-1VB1C104K). Using
this capacitor the actual safety timer will be 4.3 hours.
7. Determine TS resistor network for an operating temperature range from 0°C to 45°C.
VTSB
RT1
TS
RT2
RTH
103AT
Figure 13. TS Resistor Network
Assuming a 103AT NTC Thermistor on the battery pack, determine the values for RT1 and RT2 using the
following equations:
RT2 =
V_O(VTSB) ´ RTH_COLD ´ RTH_HOT ´
1
1
V_LTF ^- V_HTF
( ) ( ) ^{RTHHOT ´}
V_O(VTSB)
V_HTF
-1
- RTH_COLD ´
V_O(VTSB)
V_LTF
-1
RT1 =
V_O(VTSB)
V_LTF
-1
1
1
RT2 ⁺ RTH_COLD
Where:
V_LTF = V_O(VTSB) ´ % _LTF¸100 / 100
V_HTF = V_O(VTSB) ´ % _HTF¸100 / 100
(23)
RTH_COLD + 27.28 kW
RTH_HOT + 4.912 kW
RT1 + 9.31 kW
RT2 + 442 kW
(24)
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