The feedback loop of the system decides when to cut off the circuit when a transient event occurs and when to turn the system on once the event has been surpassed. To perform this task effectively, the feedback loop needs to have a fast response to the transient events. If the response is delayed, the system can become unstable and lead to turning off the output voltage.

In this system, the loop response depends on op-amp response time, OVP response of hot-swap, and FET ON/OFF response time.

The FET ON/OFF response time depends on the gate drive of TPS23521 which has a strong source current of 400µA and a strong sink current of 1A, resulting in a fast ON/OFF response. The OV response time of TPS23521 is 4µs which is also very small. So, the op-amp response is very critical. An op-amp needs to be chosen which can respond within sub µs. OPA863 is chosen in this application which has a slew rate of 105V/µs.