To improve the safety of charging Li-ion batteries, the JEITA guideline was released on April 20, 2007. The guideline emphasized the importance of avoiding a high charge current and high charge voltage at certain low and high temperature ranges.

To initiate a charge cycle, the voltage on TS pin, as a percentage of V_REGN, must be within the V_{T1_FALL%} to V_{T5_RISE%} thresholds. If the TS voltage percentage exceeds the T1-T5 range, the controller suspends charging, a TS fault is reported and waits until the battery temperature is within the T1-T5 range.

At cool temperature (T1-T2), JEITA recommends the charge current to be reduced to 20% of I_CHG. At warm temperature (T3-T5), JEITA recommends charge voltage less than 4.1 V.

Figure 9-6 JEITA Profile (BQ25616J)

Equation 3 through Equation 4 describe how to calculate resistor divider values on the TS pin.

Figure 9-7 TS Pin Resistor Network

Equation 3.

Equation 4.

In the equations above, R_{NTC, T1} is the NTC thermistor resistance value at temperature T1 and R_{NTC, T5} is the NTC thermistor resistance value at temperature T5. Selecting a 0°C to 60°C range for a Li-ion or Li-polymer battery then:

• R_NTC,T1 = 27.28 kΩ (0°C)
• R_NTC,T5 = 3.02 kΩ (60°C)
• RT1 = 5.3 kΩ
• RT2 = 31.14 kΩ