7.3.12 Overvoltage Protection

The TPS54560B incorporates an output OVP circuit to minimize voltage overshoot when recovering from output fault conditions or strong unload transients in designs with low output capacitance. For example, when the power supply output is overloaded the error amplifier compares the actual output voltage to the internal reference voltage. If the FB pin voltage is lower than the internal reference voltage for a considerable time, the output of the error amplifier increases to a maximum voltage corresponding to the peak-current-limit threshold. When the overload condition is removed, the regulator output rises, and the error amplifier output transitions to the normal operating level. In some applications, the power-supply-output voltage can increase faster than the response of the error-amplifier output resulting in an output overshoot.

The OVP feature minimizes output overshoot when using a low-value output capacitor by comparing the FB pin voltage to the rising OVP threshold, which is nominally 109% of the internal voltage reference. If the FB pin voltage is greater than the rising OVP threshold, the high-side MOSFET is immediately disabled to minimize output overshoot. When the FB voltage drops below the falling OVP threshold, which is nominally 106% of the internal voltage reference, the high-side MOSFET resumes normal operation.