bq24160, bq24161
bq24163, bq24168
SLUSAO0A –NOVEMBER 2011–REVISED MARCH 2012
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External NTC Monitoring (TS)
The I2C interface allows the user to easily implement the JEITA standard for systems where the battery pack
thermistor is monitored by the host. Additionally, the bq2416x provides 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. The bq24160/3/8 enables the user to easily implement the JEITA standard for
charging temperature while the bq24161 only monitors the hot and cold cutoff temperatures and leaves the
JEITA control to the host. The JEITA specification is shown in.
1°C
0.5°C
Portion of spec not covered by TS
4.25 V
Implementation on bq24160
4.15 V
4.1 V
T1
(0°C)
T2
(10°C)
T3 T4
(45°C) (50°C)
T5
(60°C)
Figure 25. Charge Current During TS Conditions
To satisfy the JEITA requirements, four temperature thresholds are monitored; the cold battery threshold (TNTC
<
0°C), the cool battery threshold (0°C < TNTC < 10°C), the warm battery threshold (45°C < TNTC <L 60°C) and the
hot battery threshold (TNTC > 60°C). These temperatures correspond to the VCOLD, VCOOL, VWARM, and VHOT
thresholds. Charging is suspended and timers are suspended when VTS < VHOT or VTS > VCOLD. When VWARM
<
VTS < VHOT, the battery regulation voltage is reduced by 140mV from the programmed regulation threshold.
When VCOLD < VTS < VCOOL, 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 31. The resistor values are
calculated using the following equations:
é
ê
ë
ù
ú
1
1
VDRV ´ RCOLD ´ RHOT ´
-
VCOLD
V
HOT û
RLO =
é
ê
ë
ù
ú
û
é
ê
ë
ù
VDRV
VDRV
RHOT ´
-1 -RCOLD ´
-1
ú
VHOT
VCOLD
û
(1)
(2)
VDRV
-1
VCOLD
RHI =
1
+
RLO RCOLD
1
Where:
VCOLD = 0.60 × VDRV
VHOT = 0.30 × VDRV
22
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