O'Reilly logo

Power Over Ethernet Interoperability Guide by Sanjaya Maniktala

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Some Practical Detection Techniques
In the inset in Fig. 3.3, we have shown the port voltage during the initial sequence. Region B is detection. The port voltage starts from zero (cable not energized) toward fully applied “48 V.” In this simplest case of detection, just two steps of voltage or current are being applied, and they are applied on the “charging” curve (ascending staircase). As per the IEEE standard, two steps (or samples) are a minimum, since we need them to eliminate diode offset from the bridge, as discussed previously. The standard also asks we ensure that the voltage levels we use for our calculations are more than 1 V apart. Using (V2 - V1)/(I2 - I1), we thus get R. This may sound very basic, and it is, but it is a viable detection ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required