LTC4290AIUJ/LTC4271IUF Class detection question

Have you confirmed the PDs are drawing the correct class currents for Class 2, 3 and 4 during the first class event?

The three waveforms show a similar voltage for the first class event.  This could mean each PD is presenting a Class 4.  But the difference can be very subtle and reading class current is the only sure way to determine this.

Please provide a waveform of the current to the PD during classification. 

If a current probe is not available, a DC voltage of 18V can be applied to the PD on Ethernet pairs 1/2 and 3/6 by splicing Ethernet cable.  

Dear Sir,

i will check the current to the PD during classification. maybe use DC voltage of 18V can be applied to the PD on Ethernet pairs 1/2 and 3/6 by splicing Ethernet cable. then check DC source current.

but, why classification have 3 finger? i have use LTC4278 PD device board to test. then LTC4290A  output port classification  is 3 finger.

Dear Sir,

i will check the current to the PD during classification. maybe use DC voltage of 18V can be applied to the PD on Ethernet pairs 1/2 and 3/6 by splicing Ethernet cable. then check DC source current.

but, why classification have 3 finger? i have use LTC4278 PD device board to test. then LTC4290A  output port classification  is 3 finger.

If the LTC4290A/LTC4271, set in Auto mode, sees a Class 4 on the first class event, it will proceed to two additional class events.  If the controller see a Class 0, 1, 2, or 3 on the first class event, it will proceed to power on the device without the additional class events. 

Since the claimed Class 2 and Class 3 PDs are resulting in three class events, this indicates these PDs are not properly providing their respective Class to the PSE and appear a Class 4.

If the LTC4290A/LTC4271, set in Auto mode, sees a Class 4 on the first class event, it will proceed to two additional class events.  If the controller see a Class 0, 1, 2, or 3 on the first class event, it will proceed to power on the device without the additional class events. 

Since the claimed Class 2 and Class 3 PDs are resulting in three class events, this indicates these PDs are not properly providing their respective Class to the PSE and appear a Class 4.