TPS548D22 monitors the feedback voltage to detect overvoltage and undervoltage conditions. When the feedback voltage becomes lower than 68% of the target voltage, the UVP comparator output goes high and an internal UVP delay time counter begins counting. After 1 ms, the device turns OFF both high-side and low-side MOSFETs drivers. If the hiccup mode is selected, then the device restarts after a hiccup delay time. UVP function is only enabled after the soft-start operation is completed.

When the feedback voltage becomes higher than 120% of the target voltage, the OVP comparator output goes high and the device latches OFF the high-side MOSFET driver and latches ON the low-side MOSFET driver until reaching the negative current limit to discharge the output. If the sensed inductor current reaches the negative current limit (negative OCP), the low-side MOSFET driver is turned OFF and the high-side MOSFET driver is turned ON for a minimum on-time to limit the inductor current exceed the negative limit to protect the low-side MOSFET during OVP discharge. With high-side MOSFET turning on for a minimum on-time, the inductor current is flowing in the positive direction but still in the negative region. After the minimum on-time, the low-side MOSFET turns on and the high-side MOSFET turns off. The inductor current continues following in the negative direction and reaches the negative current limit again. This cycle will continue until the negative OCP is not triggered anymore. At that time, the output voltage is close to being completely discharged. The high-side MOSFET stays turned off and the low-side MOSFET stays turned on until 1 ms UVP delay is completed. After the 1 ms UVP delay is completed, the device turns OFF both high-side and low-side MOSFETs drivers. If the hiccup mode is selected, then the device restarts after a hiccup delay time.