The device continuously monitors battery temperature by measuring the voltage between the TS pins and ground, typically determined by a negative temperature coefficient thermistor (NTC) and an external voltage divider. The device 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. During the charge cycle the battery temperature must be within the V_LTF to V_TCO thresholds, else the device suspends charging and waits until the battery temperature is within the V_LTF to V_HTF range.

Figure 8-6 TS Resistor Network

When the TS fault occurs, the fault register REG0C[2:0] indicates the actual condition on each TS pin and an INT is asserted to the host. The STAT pin indicates the fault when charging is suspended.

Figure 8-7 TS Pin Thermistor Sense Thresholds

Assuming a 103AT NTC thermistor on the battery pack as shown in Figure 8-6, the value RT1 and RT2 can be determined by using Equation 2:

Equation 2.

Select 0°C to 45°C range for Li-ion or Li-polymer battery,
RTH_COLD = 27.28 kΩ
RTH_HOT = 4.91 kΩ
RT1 = 5.21 kΩ
RT2 = 29.87 kΩ