SLUS634F November 2004 – January 2022 TPS2384
PRODUCTION DATA
After a successful discovery of a valid PD, the TPS2384 enters the classification function that identifies the power level based on the PD's current signature. The classification current level is measured at a reduced terminal voltage of 17.5 V. During classification the power dissipation can be at its highest; therefore, to prevent overtemperature shutdown in auto mode, only one port classifies at a time. When multiple ports successfully discover and proceed to classification at the same time the auto sequencer processes each request separately allowing only one port to enter classification. Figure 8-5 shows all four ports successfully detecting a valid PD at the same time and then the classification of each port occurring separately.
Upon completion of classification, the port classification register is updated. In AM mode, this information is not used but for semi-auto mode the class information can be used for power management. Figure 8-6 shows actual class currents and the class assignment which were stored in the register. These assignments are compliant with the IEEE 802.3af Standard