The thermal protection behavior can be split up into three categories of events that can happen. Figure 7-14 shows each of these categories.

1. Relative thermal shutdown: The device is enabled into an overcurrent event. The output current rises up to the I_ILIM level and the FLT goes low. With this large amount of current going through the junction temperature of the FET increases rapidly with respect to the controller temperature. When the power FET temperature rises T_REL amount above the controller junction temperature ΔT = T_FET – T_CON > T_REL, the device shuts down. For auto-retry version, after t_RETRY, the part tries to restart. The latch version requires EN to be toggled to re-enable the channel. The FLT pin is asserted until the fault condition is cleared. The first plot in Figure 7-14 shows the relative thermal shutdown behavior for the auto-retry version.
2. Absolute thermal shutdown: the device is still enabled in an overcurrent event. However, in this case the junction temperature rises up and hits an absolute reference temperature, T_ABS, and then shuts down. For auto-retry version, the device does not recover until both T_J < T_ABS – T_hys and the t_RETRY timer has expired. For latch version, toggling EN is required to re-enable the channel. The second plot in Figure 7-14 shows the absolute thermal shutdown behavior for the auto-retry version.
3. Latch behavior: the device is enabled into an overcurrent event. The DIAG_EN pin is high so that diagnostics can be monitored on SNS and FLT. For the latched version of the device, if the part shuts down due to a thermal fault, either relative thermal shutdown or absolute thermal shutdown, the device does not enable the channel until the EN pin is toggled. The third plot in Figure 7-14 shows the relative thermal shutdown behavior for the variants with LATCH pin when LATCH pin is HIGH.

Figure 7-14 Thermal Behavior