LTC4290 design and the IEEE 802.3bt compatibility

Question

We have a two years old 4 port LTPoE++ (LTC4290A, first four ports) design based on the DC1843B demonstration kit. 
 Is it possible to modify this existing hardware (e.g.: by simply changing the LTC4290A to a LTC4292) to get a fully IEEE 802.3bt (PoE++) Type 4 (~100 W) compliant equipment? Or is it only possible with a full redesign of the product? 
 Thank you very much for any help in advance.

dreyeslt · Answer

The LTC4291-1/LTC4292 chipset is specifically for IEEE 802.3bt 4-pair power. In this system, 2 power channels drive the 4 Ethernet pairs. A properly implemented LTPoE++ PSE will have a single power channel driving the 4 pairs. These are two different implementations. In addition, the LTC4291-1/LTC4292 chipset will have different pin outs than the LTC4271/LTC4290A chipset and are not interchangeable. 
 Additional note, the DC1843B is a demonstration kit for an 8-port, IEEE 802.3at (Type 2, 25.5W) PSE. One power channel per port driving 2 pairs.

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LTC4290 design and the IEEE 802.3bt compatibility

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