Stages of
powering up a PoE link
| Stage |
Action |
Volts specified
per 802.3af |
Volts managed
by chipset (LM5071) |
| Detection |
Measure whether
powered device has the correct signature resistance of 15–33
kΩ |
2.7-10.0 |
1.8–10.0 |
| Classification |
Measure which power
level class the resistor indicates (see below) |
14.5-20.5 |
12.5–25.0 |
| Startup |
Where the powered
device will startup |
>42 |
>38 (LM5072) |
| Normal operation |
Supply power to
device |
36-57 |
25.0–60.0 |
Power levels
available
| Class |
Usage |
Maximum Power Levels
at Input of Powered Device
Watt |
| 0 |
Default |
0.44 to 12.94 |
| 1 |
Optional |
0.44 to 3.84 |
| 2 |
Optional |
3.84 to 6.49 |
| 3 |
Optional |
6.49 to 12.95 |
| 4 |
Reserved |
(PSEs classify as
Class 0) |
|