802.3at has a start-up current and time limitation, providing type 2 PSE compatibility for type 1 PDs. A type 2 PSE limits output current to from 400 mA to 450 mA for up to 75 ms after power up (applying 48 V to the PI) to mirror type 1 PSE functionality. The type 2 PSE supports higher output current after 75 ms. The TPS23754 implements a 140-mA inrush current, which is compatible with all PSE types. A high-power PD must control its converter start-up peak and operational currents drawn to less than 400 mA for 80 ms. The TPS23754 device's internal soft-start permits control of the converter start-up; however, the application circuits must assure that their power draw does not cause the PD to exceed the current/time limitation. This requirement implicitly requires some form of powering down sections of the application circuits. T2P becomes valid within tT2P after switching starts, or if an adapter is plugged in while the PD is operating from a PSE.