The LMR23615 is protected from overcurrent conditions by cycle-by-cycle current limit on both the peak and valley of the inductor current. Hiccup mode is activated if a fault condition persists to prevent overheating.

High-side MOSFET overcurrent protection is implemented by the nature of the peak-current-mode control. The HS switch current is sensed when the HS is turned on after a set blanking time. The HS switch current is compared to the output of the error amplifier (EA) minus slope compensation every switching cycle. See Section 7.2 for more details. The peak current of HS switch is limited by a clamped maximum peak current threshold I_{HS_LIMIT}, which is constant. Thus the peak current limit of the high-side switch is not affected by the slope compensation and remains constant over the full duty-cycle range.

The current going through LS MOSFET is also sensed and monitored. When the LS switch turns on, the inductor current begins to ramp down. The LS switch does not turn OFF at the end of a switching cycle if its current is above the LS current limit I_{LS_LIMIT}. The LS switch is kept ON so that inductor current keeps ramping down, until the inductor current ramps below the LS current limit I_{LS_LIMIT}. Then the LS switch turns OFF, and the HS switches on, after a dead time. This is somewhat different than the more typical peak-current limit and results in Equation 10 for the maximum load current.

Equation 10.

If the current of the LS switch is higher than the LS current limit for 64 consecutive cycles, hiccup-current-protection mode is activated. In hiccup mode, the regulator is shut down and kept off for 5 ms, typically, before the LMR23615 tries to start again. If an overcurrent or short-circuit fault condition still exist, hiccup repeats until the fault condition is removed. Hiccup mode reduces power dissipation under severe overcurrent conditions, prevents over-heating and potential damage to the device.