Transition Networks
M/GE-ISW-SFP-01-PD User Guide
33668 Rev. A
http://www.transition.com/
Page 12 of 16
PoE Standards and Power Classifications
The original IEEE 802.3af-2003
PoE
standard provides up to 15.4 W of DC power (minimum 44 V DC
and 350 mA) to each device.
The updated IEEE 802.3at-2009 PoE standard also known as
PoE+
or PoE plus, provides up to 25.5 W
of power. The 2009 standard prohibits a powered device from using all four pairs for power.
Both of these amendments have since been incorporated into the IEEE 802.3-2012 publication.
Standard PoE Parameters Comparison (
Wikipedia)
Property
802.3af (802.3at Type 1)
802.3at Type 2
Power available at PD
12.95 W
25.50 W
Maximum power
delivered by PSE
15.40 W
30.0 W
Voltage range (at PSE)
44.0–57.0 V
50.0–57.0 V
Voltage range (at PD)
37.0–57.0 V
42.5–57.0 V
Maximum current
350 mA
600 mA per mode
Maximum cable
resistance
20 Ω (Category 3)
12.5 Ω (Category 5)
Power management
Three power class levels
negotiated at initial connection
Four power class levels negotiated at initial
connection or 0.1 W steps negotiated
continuously
Derating of maximum
cable ambient operating
temperature
None
5°C with one mode (two pairs) active
Supported cabling
Category 3 and Category 5
[1]
Category 5
Supported modes
Mode A (endspan), Mode B
(midspan)
Mode A, Mode B
Note
: More stringent cable specification allows assumption of more current carrying capacity and lower
resistance (20.0 Ohms for Category 3 versus 12.5 Ohms for Category 5).
