1. Introduction
Connected devices increasingly rely on PoE (Power over Ethernet) to simplify wiring and enable smarter deployments. Integrated RJ45 connectors with magnetic components—often called MagJacks—must reliably carry both data and power. Understanding their current ratings is critical when designing network hardware to meet IEEE PoE standards. In this post, we clarify typical current ratings, highlight influencing factors, and showcase LINK-PP’s MagJack solutions.
2. Current Ratings: Not a One-Size-Fits-All
Integrated RJ45 connector current ratings vary depending on:
Contact metallurgy and plating (e.g., pure copper with thick gold plating improves conductivity).
Connector geometry, such as pin size, spacing, and thermal management.
Signal vs. power usage—standard Ethernet uses minimal current (< 100 mA), whereas PoE pushes contacts to their limits.
LINK-PP specifies up to 750 mA per contact in its PoE+ LPJG0926HENL model.
3. How PoE Standards Define Current Requirements
PoE Type | Max Delivered Power | Typical Voltage | Current per Pair | Number of Pairs | Total Current |
|---|---|---|---|---|---|
IEEE 802.3af (PoE) | 12.95 W (to PD) | 44–57 V | 350 mA | 2 | ≈ 0.35 A (standard conservative) |
IEEE 802.3at (PoE+) | 25.5 W | 50–57 V | 600 mA | 2 | ≈ 0.6 A per pair ×2 = 1.2 A |
IEEE 802.3bt Type 3 | 51 W | 50–57 V | 600 mA | 4 | ≈ 0.6 A ×4 = 2.4 A |
IEEE 802.3bt Type 4 | 71.3 W | 52–57 V | 960 mA | 4 | ≈ 0.96 A ×4 = 3.84 A |
While theoretical current is derived from power ÷ voltage, IEEE defines vault limits per pair. This ensures consistent connector qualification and thermal safety.
4. Example: LINK-PP LPJG0926HENL PoE+ Connector
The LPJG0926HENL PoE+ MagJack supports IEEE 802.3at with a current rating of 720mA per contact. Since PoE+ uses two pairs, this per-contact rating provides ample margin for reliability in real-world use.
This type of margin is essential for long-term performance in compact designs, where heat buildup and multiple thermal cycles may occur.
5. Design Implications & Best Practices
★ Select connectors with margin: Choose components rated above the minimum standard current. LINK-PP’s MagJacks typically exceed base requirements.
★ Verify datasheet conditions: Ensure current rating is at 25 °C ambient with ≤20 °C temperature rise.
★ Consider four-pair use: For PoE++ designs, ensure connectors are certified for IEEE 802.3bt Type 3 or 4, meaning ≥600 mA or ≥960 mA per pair.
★ Match cable, transformer, PCB: Each segment from connector to magnetics, traces, and cable affects overall power path and temperature.
6. Conclusion
Integrated RJ45 MagJacks are designed to meet specific current demands based on PoE standards.
While a generic connector may support 1–2 A per contact, reliable deployment demands matching to standard current requirements per pair.
LINK-PP’s MagJacks—especially models like LPJG0926HENL—offer robust ratings (1.5 A/contact) with IEEE 802.3at support.
For future-proof, high-power PoE designs, ensure connectors support Type 3 or 4 (≥600 mA–960 mA per pair).
