Würth Elektronik Cross Reference to VOOHU RJ45 Jacks and Transformers

What to check before you switch from a Würth part

The Würth MagJack pairs on this page have the most detailed reports: each was checked hole by hole against both datasheets. The other Würth pairs link to comparison reports. Here is what those reports say to check.

MagJacks (RJ45 jacks with integrated magnetics)

• Shield-pin holes. On the three tab-down parts (7499111001A, 7499111121A, 7499211121A), Würth places 2 × Ø1.6 mm shield-pin holes on 15.49 mm centres and VOOHU places 2 × Ø1.63 mm holes on 15.75 mm centres, 0.26 mm wider. An existing Würth footprint needs those two holes re-checked against the VOOHU drawing. On the tab-up 7499010121A the spacing is 16.0 mm on both, with Ø1.60 mm against Ø1.63 mm holes.
• Locating pegs. All four reports list recommended peg holes of Ø3.25 mm (Würth) against Ø3.20 mm (VOOHU), on the same 11.43 mm spacing.
• Isolation test time. Würth tests for 1 minute (1500 V RMS; 2250 V DC on 7499010121A). The VOOHU datasheets state 2250 V DC at 1 mA for 6 s, plus 1500 V AC on three of the four. Your incoming inspection and safety file have to name one condition, so agree it with us before release.
• PoE (7499211121A). Both parts have built-in bridge rectifiers with the PoE output on pins 9 (+) and 10 (−). Würth states up to 350 mA per centre tap; the VOOHU datasheet states a line current of 350 mA max at 57 V DC continuous. The two are worded differently, so check each against your PD's input current.
• Plating and electrical bands. For 7499010121A, contact gold is 30 µin (Würth) against 6 µin (VOOHU). Return loss and crosstalk use different frequency bands in the 7499010121A and 7499211121A reports, and LED forward voltage is given as one range by Würth and per colour by VOOHU.

RJ45 jacks without magnetics (615008140621, S17100092)

• These two reports compare features — port count, tab orientation, through-hole mounting, LEDs, shielding and, for 615008140621, temperature — and list the same entries on both sides. They do not compare hole positions or body dimensions, so overlay the two drawings before you reuse a footprint.

LAN transformer (7490220122)

• PoE current. Würth lists the 7490220122 at 1000 mA per centre tap for IEEE 802.3bt (4PPoE); the WHSG24719PTG datasheet states a 900 mA current capability. Check the load current of your PoE class against both ratings, especially in a 4PPoE design.
• Ratings and tolerances. Operating temperature is −40 to +105 °C (Würth) against −40 to +85 °C (VOOHU), and the turns ratio 1:1 ±2% against 1CT:1CT ±5%. OCL is 350 µH min on both, measured at 24 mA DC bias by Würth and at 8 mA by VOOHU, so the two figures are not a like-for-like comparison.

Push-pull transformers

• 78931812505 and WH41-111. The turns ratio is 1:1.13 ±2% against 1:1.1, and the volt-second rating 9.5 Vµs (N1-2) against 8.6 Vµs (N1, bipolar waveform). Leakage inductance is ≤600 nH at 100 kHz / 100 mV against ≤1.0 µH at 100 kHz / 0.01 V; the test voltages differ, so the two figures are not a direct ranking. The insulation test is 2500 V AC at 1 mA on both, for 1 s (Würth) and 60 s (VOOHU). In a push-pull supply the turns ratio sets the isolated output voltage, so recalculate the output, and check the volt-second rating against your driver's input voltage and switching frequency.
• 750315371, 750316819 and 78931812505 are marked "Comparison only — see report". For 750315371 the report gives inductance, DCR and insulation tests under different conditions; for 750316819 the outline, land pattern and OCL line up, but the DCR and volt-second values use different definitions. Read the report before you plan around any of them.