The major part of the short circuit detection scheme operates with comparator CP2 comparing an image of the inductor current KL.IL, where KL.IL is proportional to the current flowing through switch SH, to a predefined reference IREF1. Comparator CP2 could be a current or voltage comparator. During normal operation of the buck converter, the transition from demagnetization (SH OFF and LS ON) to magnetization (SH ON and LS OFF) causes the LX voltage to ring, due to parasitics at the LX node. Consequently all sensed currents and voltages around these transitions must be properly handled in order to avoid false triggering of the current limit ILIM_EVENT. In order to ensure a proper detection of the peak current limit ILIM_COMP_OUT, from comparator CP2, a MASKER is used. The MASKER will mask the information provided by comparator CP2 for the first few nanoseconds of the magnetization phase, as is known in the art. This delay lets the input signals ILIM_COMP_OUT and MASK_ON settle before being compared. In normal operation, the triggering of comparator CP2 right after MASK_ON goes low never occurs.

In the event of a short circuit at VOUT, the current of inductor L, KL.IL, will rapidly build up and comparator CP2 will be triggered as soon as MASK_ON goes low. Signal ILIM_COMP_OUT high sets signal ILIM_EVENT high, and ORI emits signal STOP, forcing magnetization MAG signal to ‘0’. Signals MASK_ON and ILIM_COMP_OUT are also used to set signals SHORTCIRCUIT_STATE and LOOP_CONTROL_EVENT, in the regulation loop when a short circuit event is detected. In this way, MASK_ON and ILIM_COMP_OUT are used to detect a short circuit event in the buck converter.