JAJSES8B October 2017 – November 2018 TPS2372
The waveforms of Figure 17 demonstrate detection, classification including Autoclass during the first class event, and startup from a PSE with Type 3 Class 6 hardware classification. The key waveforms shown are V(VDD-VSS), V(RTN-VSS) and IPI. IEEE 802.3bt requires a PSE allocating Class 6 level of power to generate a minimum of two detection levels, four class and mark cycles, and startup from the fourth mark event. As shown below, the required minimum duration of the first class event has been extended for Type 3 and 4 PSEs. VRTN to VSS falls as the TPS2372 charges CBULK following application of full voltage. In Figure 19, assertion of the PG signal is delayed and used to enable load current as seen in the IPI waveform.