7.3.4.5 Thermal Protection Behavior

Both the absolute temperature thermal shutdown and the dynamic temperature thermal swing diagnostic and protection are built into the device to increase the maximum reliability of the power FET. Thermal swing is active when the temperature of the power FET is increasing sharply, that is ΔT = T_DMOS – T_Logic > T_sw, then the output is shut down, and the ST pin goes low, or the CS pin is pulled up to V_CS,h. It auto-recovers and clears the fault signal until ΔT = T_DMOS – T_Logic < T_sw – T_hys. Thermal swing function improves device reliability against repetitive fast thermal variation, as shown in Figure 37. Multiple thermal swings are triggered before thermal shutdown happens. Thermal shutdown is active when absolute temperature T > T_SD. When active, the output is shut down, and the ST pin goes low, or the CS pin is pulled up to V_CS,h. The output is auto-recovered when T < T_SD – T_hys; the current limit is reduced to I_lim,tsd, or half of the programmable current limit value, to avoid repeated thermal shutdown. However, the thermal shutdown fault signal and half-current limit value are not cleared until the junction temperature decreases to less than T_SD,rst.

Figure 37. Thermal Behavior