HyperLink Technologies CAT5 Data Line Power-Over-Ethernet Surge Protectors

Hyperlink Technologies Inc. offers an extensive line of coaxial and data line surge protectors. This paper will concentrate on the latter, specifically CAT5 Power Over Ethernet (PoE) surge protectors.

Industry Standard 802.3af outlines the requirements of CAT5 PoE. Some documents reference the term 802.11af instead and this has become the most commonly used term. CAT5 PoE allows remote equipment to be powered via it’s CAT5 cable. There are two methods of powering the equipment outlined in the 802.3af document, mode A and mode B. Mode A uses the data pairs on pins 1-2 and 3-6 to carry the DC power. In this case, the data and DC power share the same wire pairs. The spare pairs on pins 4-5 and 7-8 are unused. Mode B uses the spare pairs on pins 4-5 and 7-8 to carry the DC power. Data is carried on the normal pairs of 1-2 and 3-6. 802.3af mode B is the most common method used to power remote equipment. The DC power polarity and amplitude varies depending on manufacturer.

Hyperlink Technologies sells surge protectors that support both modes A and B as well as normal or reverse DC polarity. Hyperlink offers two basic, CAT5 PoE surge protectors. The first is a single stage shunt protector. The second style is a multi stage series-shunt protector. Variations of each type depend on the required surge power rating. All surge protectors offer some level of surge protection from conducted or induced transients. The transients will have both a differential and common mode component for the conducting wire or pairs of wires. The level of protection is based on the protector topology, component surge power ratings and the requirement for a low impedance earth ground to connect to. The other basic requirement of a surge protector is to provide minimal insertion loss, cross talk, reflections and distortion of data signals. If the protector also carries AC or DC power, resistive losses should be minimized.

Figure 2 shows the base Hyperlink outdoor POE surge protector, the AL-CAT5VW

Figure 2

The AL-CAT5VW provides affordable surge protection for a typical client installation. It is a single stage shunt design offering both differential and common surge protection to all lines. The user interface is two RJ-45, 8 pin jacks. The data path utilizes a low capacitance, polymer device to protect the balanced CAT5 signals without degrading them. The power path is comprised of an array of bi-directional clamping diodes.

Figure 3 shows the mid grade Hyperlink outdoor POE surge protector, the AL-CAT5W.

Figure 3
AL-CAT5W

The AL-CAT5W provides affordable surge protection for a typical hub or client installation. It is a single stage shunt design offering both differential and common surge protection to all lines. The user interface is two RJ-45, 8 pin jacks and a removable 8 pin terminal strip. The use of high power semiconductor diodes increases the surge rating of the design. The data path utilizes a low capacitance, bridge architecture, to protect the balanced CAT5 signals without degrading them. The power path is comprised of an array of bi-directional clamping diodes.

Figure 4 shows the professional grade Hyperlink high power outdoor POE surge protector, the AL-CAT5HPW.

Figure 4
AL-CAT5HPW

The AL-CAT5HPW provides the maximum surge protection for a typical hub or client installation. It is a multi stage series-shunt protector offering both differential and common surge protection to all lines with an added failsafe provision. The user interface is two RJ-45, 8 pin jacks and a removable 8 pin terminal strip. The three stages of the AL-CAT5HPW work in concert to raise the power rating of the protector. In the data path, the first stage is comprised of a differential gas discharge tube. Stage two is a pair of current limiting series fusible resistors and the third stage is a high speed, low capacitance diode clamp array. In the power path, the first stage is comprised of a differential gas discharge tube. Stage two is a pair of filter inductors and the third stage is comprised of an array of bi-directional clamping diodes.

The advantage of the AL-CAT5HPW three stage surge protector design is the added level of protection due to its large power rating and safety due to its failsafe architecture. The design marries the high power handling capacity of slow gas tubes with the high-speed response of low power diodes.

For the data path, when a transient event occurs, the high-speed diode array conduct first, clamping the voltage to a safe level. The series fusible resistors limit the maximum current the diodes must withstand. The high power differential gas tubes, which are slower than the diodes, then turn on. Once the gas inside the tubes ionize, the shunt voltage across the tube drops. The use of a three-wire differential gas discharge tube provides superior common and differential mode protection against conducted and induced transients, versus the use of lower cost two wire tubes. A differential gas tube will protect both wires of the pair even if the transient is present only on a single wire of the pair. In the event of a catastrophic surge event, the series resistors will fuse and the shunt diodes will short. This will safely disconnect the line form the datacom equipment.