The UCG28826 offers overtemperature protection to prevent system operation at excessively high temperatures and limit the components from exceeding their maximum ambient temperature ratings. The device has separate internal overtemperature protection to limit the die temperature and an external overtemperature protection to monitor and limit the system temperature using a resistor with negative temperature coefficient (NTC). The internal overtemperature fault triggers when die temperature exceeds 150℃ and switching stops. The device recovers to normal operation and switching resumes when the die temperature reduces below 140℃. The internal overtemperature protection is an auto-retry fault.

For the external overtemperature fault, connect the NTC between the FLT and AGND pins. To check for this fault, a 75μA current is sourced from the FLT pin through the external resistor to ground. This current is sourced for a 250μs on-time in every 10ms time period. An up-down counter increments every time when V_FLT is lower than 0.6V (typ.) with the sourced current. This counter decrements when V_FLT is higher than 0.66V (typ.) with a 60mV hysteresis during the 250μs duration. An external overtemperature fault is declared at a count of three, and this is a latched fault. The external overtemperature protection and 75μA sourcing current is disabled during burst mode operation to give <30mW (typ.) no-load system power consumption.