ZHCSPK7F 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.
Figure 8-5 Four Port Discovery, Class, Power OnUpon 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
Figure 8-6 Class Current and Class Assignments