The TPS54325-Q1 has cycle-by-cycle overcurrent limiting control. The inductor current is monitored during the off state and the controller keeps the off state when the inductor current is larger than the overcurrent trip level. In order to provide both good accuracy and cost effective solution, the device supports temperature compensated internal MOSFET R_DS(on) sensing.

The inductor current is monitored by the voltage between PGND pin and SW1 and SW2 pins. In an overcurrent condition, the current to the load exceeds the current to the output capacitor, thus the output voltage tends to fall off. Eventually, the output voltage ends up crossing the undervoltage protection threshold and shutdown.