SLVSF02D March 2019 – May 2020 TPS23881
Although the supported VPWR supply voltage range is 44 V to 57 V, a power supply with a 50 V minimum output is required to provide PoE power levels from 30 W up to 60 W over 2-pair and 4-pair, and a 52 V minimum power supply is required to comply with Type-4 (up to 90W) IEEE requirements. The TPS23881 requires approximately 10-mA typical and 12-mA maximum from the VPWR supply, but the total output current required from the VPWR supply depends on the number and type of ports required in the system. The TPS23881 can be configured to support either 15.5 W, 30 W, 45 W, 60 W, 75W, or 90 W per port and the power limit is set proportionally at turn on. The port power limit, PCUT, is also programmable to provide even greater system design flexibility. However, it is generally recommend to size the VPWR supply accordingly to the PoE Type to be supported. As an example, a 130 W or greater power supply would be recommended for eight type 1 (15.5 W each) ports, or a 500 W or greater power supply is recommended for eight 4-pair type 3 (60 W) ports, assuming maximum port and standby currents.
In IEEE complaint applications, only 4-Pair configured ports are capable of supporting power levels greater than 30 W.