7.3.3 Over Current and Short Circuit Protection

The TPS563231 is protected from over-current conditions by cycle-by-cycle current limit on the valley of the inductor current. Hiccup mode will be activated if a fault condition persists to prevent over-heating.

The current going through low-side (LS) MOSFET is sensed and monitored. When the LS MOSFET turns on, the inductor current begins to ramp down. The LS MOSFET will not be turned OFF if its current is above the LS current limit I_{LS_LIMIT} even the feedback voltage, V_FB, drops below the reference voltage V_REF. The LS MOSFET 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 MOSFET is turned OFF and the HS switch is turned on after a dead time.

As the inductor current is limited by I_{LS_LIMT}, the output voltage tends to drop as the inductor current may be smaller than the load current. Hiccup current protection mode is activated once the V_FB drops below the UVP threshold after a delay time (800 µs typically). In hiccup mode, the regulator is shut down and kept off for 24 ms typically before the TPS563231 try to start again. If over-current or short-circuit fault condition still exists, hiccup will repeat until the fault condition is removed. Hiccup mode reduces power dissipation under severe over-current conditions, prevents over-heating and potential damage to the device.