The BQ25157 monitors the TS voltage and sends an interrupt to the host whenever it crosses the V_HOT, V_WARM, V_COOL and V_COLD thresholds which correspond to different temperature thresholds based on the NTC resistance and biasing. These thresholds may be adjusted through I²C by the host. The device will also disable charging if TS pin exceeds the V_{TS_OPEN} threshold.

The TS biasing circuit is shown in Figure 9-8. The ADC range is set to 1.2 V. Note that the respective V_TSand hence ADC reading for T_COLD (0°C), T_COOL (10°C), T_WARM (45°C) and T_HOT (60°C) changes for every NTC, therefore the threshold values may need to be adjusted through I²C based on the supported NTC type.

Figure 9-8 TS Bias Functional Diagram

The BQ25157 supports by default the following thresholds for a 10-KΩ NTC.

For accurate temperature thresholds a 10-KΩ NTC with a 3380 B-constant should be used (Murata NCP03XH103F05RL for example) with a parallel 10-KΩ resistor. Each threshold can be programmed via I²C through the TS_COLD, TS_COOL, TS_WARM and TS_HOT registers. The value in the registers corresponds to the 8 MSBs in the TS ADC output code.