BQ24165_14 Datasheet, PDF (20/38 Pages) Texas Instruments – 2.5A, Dual-Input, Single Cell Switch Mode Li-Ion Battery Charger with Power Path Management

bq24165
bq24166
bq24167
SLUSAP4B – DECEMBER 2011 – REVISED MARCH 2013
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EXTERNAL NTC MONITORING (TS, bq24166/7)
The bq24166 and bq24167 provide a flexible, voltage based TS input for monitoring the battery pack NTC
thermistor. The voltage at TS is monitored to determine that the battery is at a safe temperature during charging.
For the bq24166, two temperature thresholds are monitored; the cold battery threshold (T_NTC < 0°C) and the hot
battery threshold (T_NTC > 60°C). These temperatures correspond to the V_COLD and V_HOT thresholds. Charging is
suspended and timers are suspended when V_TS < V_HOT or V_TS > V_COLD.
To satisfy the JEITA requirements, the bq24167 monitors four temperature thresholds; the cold battery threshold
(T_NTC < 0°C), the cool battery threshold (0°C < TNTC < 10°C), the warm battery threshold (45°C < T_NTC < 60°C)
and the hot battery threshold (T_NTC > 60°C). These temperatures correspond to the V_COLD, V_COOL, V_WARM, and
V_HOT thresholds. As with the bq24166, charging is suspended and timers are suspended when V_TS < V_HOT or V_TS
> V_COLD. When V_HOT < V_TS < V_WARM, the battery regulation voltage is reduced by 140mV from the programmed
regulation threshold. When V_COOL < V_TS < V_COLD, the charging current is reduced to half of the programmed
charge current.
The TS function is voltage based for maximum flexibility. Connect a resistor divider from DRV to GND with TS
connected to the center tap to set the threshold. The connections are shown in Figure 24. The resistor values are
calculated using the following equations:
RLO =
V_DRV
´ RCOLD ´ RHOT ´
é1
ê
ë
V_COLD
-
1
V_HOT
ù
ú
û
RHOT ´
é
ê
V_DRV
ù
- 1_ú - RCOLD
´
é
ê
V_DRV
ù
- 1_ú
ë ^VHOT û
ë ^VCOLD û
(3)
RHI =
V_DRV
V_{COL D}
-1
1
1
+
RLO RCOLD
(4)
Where:
V_COLD = 0.60 × V_DRV
V_HOT = 0.30 × V_DRV
Where RHOT is the NTC resistance at the hot temperature and RCOLD is the NTC resistance at cold
temperature.
For the bq24167, the WARM and COOL thresholds are not independently programmable. The COOL and
WARM NTC resistances for a selected resistor divider are calculated using the following equations:
RCOOL =
RLO ´ 0.564 ´ RHI
RLO - RLO ´ 0.564 - RHI ´ 0.564
(5)
RW ARM =
RLO ´ 0.383 ´ RHI
RLO - RLO ´ 0.383 - RHI ´ 0.383
(6)
20
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