The device continuously monitors battery temperature by measuring the voltage between the TS pin and ground, typically determined by a negative temperature coefficient thermistor and an external voltage divider. The device compares this voltage against its internal thresholds to determine if charge or boost 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.

For battery protection during boost mode, the device monitors the battery temperature to be within the VBCOLDx to VBHOTx thresholds unless boost mode temperature is disabled by setting BHOT bits (REG06[3:2]) to 11. When temperature is outside of the temperature thresholds, the boost mode is suspended and REG08[7:6] bits (VBUS_STAT) are set to 00. Once temperature returns within thresholds, the boost mode is recovered.

Figure 9-7 TS Resistor Network

When the TS fault occurs, the fault register REG09[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 9-8 TS Pin Thermistor Sense Thresholds in Charge Mode

Figure 9-9 TS Pin Thermistor Sense Thresholds in Boost Mode

Assuming a 103AT NTC thermistor is used on the battery pack Figure 9-8, the value RT1 and RT2 can be determined by using the following equation:

Equation 1.

Select 0°C to 45°C range for Li-ion or Li-polymer battery,
RTH_COLD = 27.28 kΩ
RTH_HOT = 4.911 kΩ
RT1 = 5.25 kΩ
RT2 = 31.23 kΩ