SLUSDU0 September 2019 BQ21061
In order to protect the device from damage due to overheating, the junction temperature of the die, TJ, is monitored. When TJ reaches TSHUTDOWN the device stops operation and is turned off. The device resumes operation when TJ falls below TSHUTDOWN by THYS.
During the charging process, the device will reduce the charging current at a rate of (0.04 x ICHARGE )/°C once TJ exceeds the thermal foldback threshold, TREG to prevent further heating. 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.
The die junction temperature, TJ, can be estimated based on the expected board performance using Equation 1:
Where PDISS is the total power dissipation in the IC. The θJA 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.