Datasheet

CHARGESUSPENDED CHARGESUSPENDED
TEMPERATURERANGE
TOINITIATECHARGE
TEMPERATURERANGE
DURING A CHARGE
CYCLE
V
LTF
V
HTF
GND
V
TCO
V
LTF
GND
V
LTFH
V
LTFH
VREF
VREF
CHARGESUSPENDED CHARGESUSPENDED
æ ö
´ ´ ´ -
ç ÷
è ø
æ ö
æ ö
´ - - ´ -
ç ÷
ç ÷
è ø
è ø
VREF COLD HOT
LTF TCO
VREF VREF
HOT COLD
TCO LTF
1 1
V RTH RTH
V V
RT2 =
V V
RTH 1 RTH 1
V V
VREF
LTF
COLD
V
1
V
RT1 =
1 1
+
RT2 RTH
-
bq24600
www.ti.com SLUS891A –FEBRUARY 2010– REVISED OCTOBER 2011
Temperature Qualification
The controller continuously monitors battery temperature by measuring the voltage between the TS pin and
GND. A negative temperature-coefficient thermistor (NTC) and an external voltage divider typically develop this
voltage. The controller compares this voltage against its internal thresholds to determine if charging is allowed.
To initiate a charge cycle, the battery temperature must be within the V
LTF
to V
HTF
thresholds. If battery
temperature is outside of this range, the controller suspends charge and the safety timer and waits until the
battery temperature is within the V
LTF
to V
HTF
range. During the charge cycle, the battery temperature must be
within the V
LTF
to V
TCO
thresholds. If battery temperature is outside of this range, the controller suspends charge
and the safety timer and waits until the battery temperature is within the V
LTF
to V
HTF
range. The controller
suspends charge by turning off the PWM charge FETs. Figure 14 summarizes the operation.
Figure 14. TS Pin, Thermistor Sense Thresholds
Assuming a 103AT NTC thermistor on the battery pack as shown in Figure 1, the value RT1 and RT2 can be
determined by using Equation 6 and Equation 7:
(6)
(7)
For example, a 103AT NTC thermestor is used to monitor the battery pack temperature. Select T
COLD
= 0ºC and
T
CUT_OFF
= 45ºC. Then we get R
T2
= 430 kΩ, R
T1
= 9.311 Ω. A small RC filter is suggested to use for
system-level ESD protection.
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