The MAXM17545 is provided with a robust overcurrent protection scheme that protects the device under overload and output short-circuit conditions. A cycle-by-cycle peak current limit turns off the internal high-side MOSFET whenever the high-side switch current exceeds an internal limit of 2.8A (typ). A runaway current limit on the high-side switch current at 3.4A (typ) protects the device under high input voltage and short-circuit conditions when there is insufficient output voltage available to restore the internal inductor current that was built up during the ON period of the step-down converter.
One occurrence of the runaway current limit triggers a hiccup mode. Additionally, if, due to a fault condition, the feedback voltage drops to 0.58V (typ) at any time after soft-start is complete, hiccup mode is triggered. In hiccup mode, the converter is protected by suspending switching for a hiccup timeout period of 32,768 clock cycles (a cycle duration is determined by the switching frequency set with the Rt resistor).
Once the hiccup timeout period expires, soft-start is attempted again. Note that, when soft-start is attempted under an overload condition, if the feedback voltage does not exceed 0.58V, the device switches at half the programmed switching frequency. Hiccup mode of operation ensures low power dissipation under output short-circuit conditions.