During operation, to protect the device from damage due to overheating, the junction temperature of the die, T_J, is monitored. When T_J reaches T_SHUTDOWN the device stops operation and is turned off. The device resumes operation when T_J falls below T_SHUTDOWN by T_HYS.

During the charging process, to prevent overheating in the device, the device monitors the junction temperature of the die and reduces the charging current at a rate of (0.04 x I_CHARGE )/°C once T_J exceeds the thermal foldback threshold, T_REG. If the charge current is reduced to 0, the battery supplies the current needed to supply the PMID output. The thermal regulation threshold may be set through I²C by setting the THERM_REG bits to the desired value.

To ensure that the system power dissipation is under the limits of the device. The power dissipated by the device can be calculated using Equation 1:

Equation 1.

Where:

Equation 2.

Equation 3.

Equation 4.

The die junction temperature, T_J, can be estimated based on the expected board performance using the following equation:

Equation 5.

The θ_JA is largely driven by the board layout. For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics Application Report. Under typical conditions, the time spent in this state is very short.