Users Guide

Switch Feature Overview 77
Over-Temperature Protection
In addition to the die thermal sensor, there are thermal sensors on each
MOSFET that continuously monitor per port main MOSFETs junction
temperature and will shut down the port load power in cases where the
temperature exceeds 200°C.
4-Pair Ports
In order to have the ability to deliver more than 30w to the PD, 4-pair
powering is used. 4-pair powering utilizes all eight Registered Jack-45 (RJ-45)
wires for delivering the power. It is implemented by utilizing two separate
front-ends, each capable of delivering maximum AT power, enabling delivery
of 60W over four pairs. The two front ends drive separate pairs and connect
together inside the PD.
The combined front ends follow certain rules:
1 Line detection:
• In case one pair fails pre-detection, the port will turn on as a 2-pair
port.
• In case both pairs pass pre-detection and fail line detection, the port
will not power on.
2 Classification:
• PD must have a mechanism that counts the number of class events
and determines the PSE type.
• 2 class events —PSE is two pairs AT.
• 4 class events —PSE is four pairs AT/UPoE.
• When one of the classes (or both) is
class error , both pairs will not turn
on.
• When the ports have different class levels, the switch will not turn on
any of the pairs.
3 Startup:
• Startup of the ports is done simultaneously with maximum gap of
10ms.
4 Port disconnection: