Does LTC4269-1 support power demotion? Power demotion was introduced in IEEE 802.3at. LTC4269-1 is a IEEE 802.3at compliant PD. Suppose I have defined LTC4269-1 in my circuit as a type 2 class 4 PD (Rclass = 30.9 Ω). If I connect the LTC4269-1 to a type 1, class 3 PSE, will it power up with the 12.95 W instead of the 25.5 W?
LTC4269-1 supports power demotion with the /T2P pin.
When a 2-event classification sequence successfully completes, the LTC4269-1 recognizes this sequence, and provides an indicator bit, declaring the presence of a IEEE 802.3at, Type 2, 25.5W PSE. The PD does this by pulling /T2P pin low. If a IEEE 802.3af ,Type 1, 12.95W PSE is connected then /T2P is not active and remains high. LTC4269-1 does not limit the port current while demoted, instead it relies on the downstream load to measure /T2P and limit its power consumption.