Transformateur LAN

It does three jobs at once: it isolates the PHY from the cable, rejects common-mode noise, and keeps the differential pair balanced.

Isolation is the one that cannot be left out — cable runs cross floors and cabinets, the two ends may not share a ground potential, and surges travel in along the cable. Common-mode rejection decides whether the port passes system EMC, and pair balance decides return loss, the first thing to degrade when link margin runs short. All three are done passively; the part performs no voltage transformation. Parts are grouped by data rate across theLAN Transformer range.

One differential pair is one channel; two channels — outgoing and returning — make a pairset; how many pairsets a port uses is set by the data rate.

100M and below take two channels, one pairset, per port; Gigabit and above take four channels across two pairsets. Counting transformer units therefore verifies port speed in reverse: a 100M part carries twice the port count in units and a Gigabit part four times. Current figures are read on the same basis — a line saying "each channel" describes one path, and only "full channels" describes the group. Rates are separated into families across theLAN Transformer range.

Work from the constraints that cannot move to the ones that can: data rate, then port count, then how the port is powered, then temperature and qualification, then package and hole pattern, and only then the finer specifications.

Getting any of the first four wrong means starting selection again, while the last two can usually still be accommodated during layout. Reversing the order is where designs go wrong — filtering by package first often lands on a part that cannot meet the temperature or power requirement, and both are fixed before design freeze. Low-profile and some compact packages currently come only in the standard temperature grade. Start from the data-rate families in theLAN Transformer range.

Read the qualifier that follows it rather than converting it yourself.

Three styles appear across this catalogue: a bare figure with no stated scope, read exactly as written; a figure marked "each channel", describing one path; and a pair of figures, as on one single-port part stating 720 mA per channel and 1440 mA for full channels, where four channels form two pairsets. The dangerous move is multiplying an "each channel" figure by the channel count and treating the result as port capability, because not every part is designed for all paths at full load at once. PoE grades are listed per part across theLAN Transformer range.

No. Matching pin count and pitch only means they group together in a parametric search; it does not mean they fit the same board, and it does not mean they perform alike.

Three things still need checking. Row spacing: the Pitch field describes the gap between adjacent pins, not the distance between rows, and this catalogue holds 20-pin parts at one pitch using three incompatible hole patterns. Internal structure: two parts in one package may differ in port count or unit count. Capability grade: temperature, isolation and power capability are often the only difference between parts in one package, and none of them shows up in package parameters. Compare the drawings item by item — browse by family in theLAN Transformer range.

VOOHU Electronics is certified to ISO 9001:2015 and ISO 14001:2015, and its products meet RoHS, REACH and CE requirements.

Some drawings additionally carry a compliance mark or name the standard a part is built to. Component-level compliance is not the same as an end-product approval — system certification still has to be completed against the standards of the target market. Compliance documents, material declarations and third-party reports for a specific part number are available from our Download Center, or we can send the current revision; a mark on a drawing does not substitute for the formal declaration. Parts are listed by family in theLAN Transformer range.