The TS pin is designed to follow the new JEITA temperature standard for Li-Ion and Li-Pol batteries. There are now four thresholds, 60°C, 45°C, 10°C, and 0°C. Normal operation occurs from 10°C to 45°C. If between 0°C and 10°C the charge current level is cut in half and if between 45°C and 60°C the regulation voltage is reduced to 4.1 Vmax, see Figure 7-4. The TS feature is implemented using an internal 50-μA current source to bias the thermistor (BQ24050 designed for use with a 10k NTC β = 3370 (SEMITEC 103AT-2 or Mitsubishi TH05-3H103F), and BQ24052 with a 100k NTC β = 3540 (Mitsubishi TH05-36104F) or equivalent) connected from the TS pin to V_SS. If this feature is not needed, a fixed 10k can be placed between TS and V_SS to allow normal operation. This may be done if the host is monitoring the thermistor and then the host would determine when to pull the TS pin low to disable charge.

The TS pin has two additional features, when the TS pin is pulled low or floated/driven high. A low disables charge (similar to a CE feature) and a high puts the charger in TTDM.

Above 60°C or below 0°C the charge is disable. Once the thermistor reaches ≉–10°C the TS current folds back to keep a cold thermistor (from –10°C to –50°C) from placing the IC in the TTDM mode. If the TS pin is pulled low into disable mode, the current is reduce to ≉30 μA, see Figure 7-2. Because the I_TS current is fixed along with the temperature thresholds, it is not possible to use thermistor values other than the 10k and 100k.