JAJSES8B October 2017 – November 2018 TPS2372
IEEE 802.3bt has a startup current and time limitation, providing compatibility between a PSE of any Type and a PD of any Type. The PSE inrush limit varies according to the allotted power. If Class 0 to 4, Class 5 to 6 or Class 7 to 8, the inrush limit is respectively from 400 mA to 450 mA, 400 mA to 900 mA or 800 mA to 900 mA. PSE inrush limit applies for up to 75 ms after power up (applying "48 V" to the PI), after which the Type 2, 3, or 4 PSE will support a higher output current in accordance with the allocated class. The TPS2372-3 and TPS2372-4 respectively implement a 200-mA and 335-mA inrush current, which is compatible with all PSE Types. A high-power PD must limit its converter startup peak current. The operational current for Type 2 and 3, and preferably Type 4, cannot exceed 400 mA for a period of 80 ms.