Top Products

  ✅ Introduction   Vertical RJ45 jacks — also known as top-entry RJ45 connectors — allow Ethernet cables to plug vertically into the PCB. While they serve the same electrical function as right-angle RJ45 ports, they introduce unique mechanical, routing, EMI/ESD, PoE, and manufacturing considerations. This guide provides a practical, PCB-designer-focused breakdown to help ensure reliable performance and clean high-speed layout.     ✅ Why Vertical / Top-Entry RJ45 Jacks?   Vertical RJ45 connectors are commonly chosen for:   Space optimization in compact systems Vertical cable entry in embedded and industrial devices Panel design flexibility when the connector sits on the top surface of a board Multi-port/dense layouts where front-panel space is limited   Applications include industrial controllers, telecom cards, compact networking devices, and test equipment.     ✅ Mechanical & Footprint Considerations   Board Edge & Chassis Fit   Align the connector opening with the enclosure/cutout Maintain clearance for cable bending and latch release Check vertical stacking and center-to-center spacing for multi-port designs   Mounting & Retention   Most vertical RJ45s include:   Signal pin row (8 pins) Shield ground posts Mechanical retention pegs   Best practices:   Anchor posts into grounded copper or inner planes for rigidity Follow the exact recommended drill and annular ring sizes Avoid substituting pad sizes without vendor review   Soldering Method   Many parts are through-hole reflow-capable Heavy shield pins may need selective wave soldering Follow the component temperature profile to prevent housing deformation     ✅ Electrical Design & Signal Integrity   ♦ Magnetics: Integrated vs. Discrete   MagJack (integrated magnetics) Smaller routing footprint, simpler BOM Shielding & grounding handled internally Discrete magnetics Flexible component selection Requires tight PHY-to-transformer routing discipline   Choose based on board density, EMI constraints, and design control requirements.   ♦​ Differential Pair Design   Maintain 100 Ω differential impedance Match lengths within PHY requirements (±5–10mm typical short-trace tolerance) Keep pairs on one layer when possible Avoid stubs, sharp corners, and plane gaps   ♦​ Via Strategy   Avoid via-in-pad unless filled & plated Minimize differential via count Match via count between pairs     ✅ PoE Design Considerations   For PoE/PoE+/PoE++ (IEEE 802.3af/at/bt):   Use connectors rated for PoE current & temperature Increase trace width and ensure copper thickness supports current Add resettable fuses or surge protection for a robust design Consider the thermal rise in connectors during continuous load     ✅ EMI, Shielding & Grounding   Shield Connection   Tie shield tabs to chassis ground (not signal ground) Use multiple stitching vias near shield tabs Optional: 0 Ω jumper or RC network between chassis and system ground   Filtering   If magnetics are integrated, avoid duplicating common-mode chokes If discrete, place CM chokes close to the RJ45 entrance     ✅ ESD & Surge Protection   ESD Clamping   Place ESD diodes very close to the connector pins Short, wide traces to ground reference Match the protection scheme to the enclosure ESD pathways   Industrial/Outdoor Surge   Consider GDTs, TVS arrays, and higher-rating magnetics Validate to IEC 61000-4-2/-4-5 where applicable     ✅ LEDs & Diagnostics   LED pins may not follow linear pin pitch — confirm footprint Route LED signals away from Ethernet pairs Add optional test pads for PHY diagnostics and PoE power lines ​   ✅ Manufacturing & Test Guidelines   1. Assembly   Provide pick-and-place fiducials For the selective wave: maintain solder keep-outs Validate stencil apertures for shield pins   2. Inspection & Test   Ensure AOI visibility around pads Provide bed-of-nails ICT access to PHY side test pads Leave room for probe points on the PoE rail & link LEDs   3. Durability   Review the rated insertion cycles if the device involves frequent patching Use reinforced connectors for industrial environments     ✅ Common Design Mistakes   Mistake Result Fix Routing over plane gaps Signal loss & EMI Maintain a continuous ground plane Incorrect length matching Link errors Match within PHY tolerance Weak mechanical anchoring Pad lift/wobble Plate retention holes & follow vendor footprint Improper ESD return System resets Place TVS near pins & use a solid GND path       ✅ PCB Designer Checklist     ● Mechanical   Follow the manufacturer's footprint exactly Confirm enclosure alignment & latch clearance Anchor shield posts into copper   ●​ Electrical   100 Ω diff pair impedance, matched lengths Minimize via count & avoid stubs Correct magnetic orientation & polarity   ●​ Protection   ESD diodes close to the connector PoE components sized for power class Proper chassis-to-ground tie method selected   ●​ DFM/Testing   AOI window clear Test pads for PHY/PoE Reflow/wave profile checked     ✅ Conclusion   Vertical (top-entry) RJ45 connectors combine mechanical constraints with high-speed and power-delivery challenges. Treat placement, magnetics, shielding, and PoE as system-level design decisions early in development. Following vendor footprints and solid EMC/ESD practices ensures robust performance and smooth manufacturing.    

Introduction In modern Power over Ethernet (PoE) systems, power delivery is no longer a fixed one-way process. As devices become more advanced — from Wi-Fi 6 access points to multi-sensor IP cameras — their power requirements change dynamically. To handle this flexibility, the Link Layer Discovery Protocol (LLDP) plays a vital role. Defined under IEEE 802.1AB, LLDP enables intelligent, two-way communication between PoE power providers (PSE) and power consumers (PD). By understanding how LLDP works within the PoE power negotiation process, network designers can ensure optimal performance, energy efficiency, and system safety.     1. What Is LLDP (Link Layer Discovery Protocol)? LLDP is a Layer 2 (Data Link Layer) protocol that allows Ethernet devices to advertise their identity, capabilities, and configuration to directly connected neighbors. Each device sends LLDP Data Units (LLDPDUs) at regular intervals, containing key information such as: Device name and type Port ID and capabilities VLAN configuration Power requirements (in PoE-enabled devices) When used with PoE, LLDP is extended through LLDP-MED (Media Endpoint Discovery) or IEEE 802.3at Type 2+ power negotiation extensions, enabling dynamic power communication between PSE and PD.     2. LLDP in the Context of PoE Standards Before LLDP was introduced, IEEE 802.3af (PoE) used a simple classification system during the initial link-up: The PD would indicate its class (0–3) The PSE would allocate a fixed power limit (e.g., 15.4 W) However, as devices evolved, this static approach became insufficient. For example, a dual-band wireless AP might need 10 W in idle but 25 W under heavy load — impossible to manage efficiently using only the legacy class method.   That’s why IEEE 802.3at (PoE+) and IEEE 802.3bt (PoE++) introduced LLDP-based power negotiation.   IEEE Version LLDP Support Power Type Max Power (PSE) Negotiation Method 802.3af (PoE) No Type 1 15.4 W Fixed class-based 802.3at (PoE+) Optional Type 2 30 W LLDP-MED optional 802.3bt (PoE++) Yes Type 3 / 4 60 W / 100 W LLDP mandatory for high power     3. How LLDP Enables PoE Power Negotiation   The LLDP negotiation process occurs after the physical PoE link is established and the PD has been detected. Here’s how it works: Step 1 – Initial Detection and Classification The PSE detects a valid PD signature (25kΩ). It applies initial power based on the PD class (e.g., Class 4 = 25.5 W). Step 2 – LLDP Exchange Once Ethernet data communication starts, both devices exchange LLDP frames. The PD sends its exact power needs (e.g., 18 W for standard mode, 24 W for full operation). The PSE replies, confirming available power per port. Step 3 – Dynamic Adjustment The PSE adjusts power output accordingly in real time. If multiple PDs compete for power, the PSE prioritizes based on available power budget. Step 4 – Continuous Monitoring The LLDP session continues periodically, allowing the PD to request more or less power as needed. This ensures safety, prevents overload, and supports energy efficiency.     4. Advantages of LLDP Power Negotiation   Advantage Description Precision Enables the PD to request exact power levels (e.g., 22.8 W) instead of predefined class values. Efficiency Prevents over-provisioning, freeing power budget for additional devices. Safety Dynamic adjustment protects devices from overheating or power surge. Scalability Supports multi-port, high-density PSE systems with optimized resource allocation. Interoperability Ensures seamless operation between devices from different vendors under IEEE standards.     5. LLDP vs Traditional PoE Classification   Feature Traditional PoE (Class-Based) LLDP PoE Negotiation Power Allocation Fixed per class (0–8) Dynamic per device Flexibility Limited High Real-Time Control None Supported Overhead Minimal Moderate (Layer 2 frames) Use Case Simple, static devices Smart, variable-load devices   In short: Class-based power assignment is static. LLDP-based negotiation is intelligent. For modern deployments — Wi-Fi 6/6E APs, PTZ cameras, or IoT hubs — LLDP is essential to fully utilize PoE+ and PoE++ capabilities.     6. LLDP in IEEE 802.3bt (PoE++) Under IEEE 802.3bt, LLDP becomes a core part of the power negotiation process, especially for Type 3 and Type 4 PSE/PD pairs delivering up to 100 W.   It supports: Four-pair power delivery Granular power requests (in 0.1 W increments) Cable loss compensation Bidirectional communication for power reallocation This allows dynamic, safe, and efficient distribution of power across multiple high-demand PDs — a critical feature for smart buildings and industrial networks.     7. Real-World Example: LLDP in Action   Consider a Wi-Fi 6 access point connected to a PoE++ switch: At startup, the PD is classified as Class 4, drawing 25.5 W. After boot, it uses LLDP to request 31.2 W to power all radio chains. The switch checks its power budget and grants the request. If more devices connect later, LLDP allows the switch to reduce allocation dynamically. This intelligent negotiation ensures: Stable operation of high-performance devices No overloading of switch power budget Efficient energy use across the network     8. LINK-PP Components Supporting LLDP-Enabled PoE Designs Reliable LLDP-based communication requires stable signal integrity and robust current handling at the physical layer. LINK-PP provides PoE RJ45 connectors with integrated magnetics optimized for IEEE 802.3at / bt compliance and LLDP-enabled systems.   Features: Integrated transformer & common-mode choke for LLDP signal clarity Supports 1.0A DC current per channel Low insertion loss and crosstalk Operating temperature: -40°C to +85°C These components ensure that power negotiation packets (LLDP frames) remain clean and reliable, even under full power load.     9. Quick FAQ Q1: Does every PoE device use LLDP? Not all. LLDP is optional in PoE+ (802.3at) but mandatory in PoE++ (802.3bt) for advanced negotiation. Q2: Can LLDP adjust power in real time? Yes. LLDP allows continuous updates between PSE and PD, adapting power allocation as workloads change. Q3: What happens if LLDP is disabled? The system falls back to class-based power allocation, which is less flexible and may under- or over-power the PD.     10. Conclusion   LLDP brings intelligence and flexibility to Power over Ethernet systems. By enabling dynamic communication between PSE and PD, it ensures each device receives just the right amount of power — no more, no less. As networks scale and devices become more power-hungry, LLDP-based PoE negotiation is essential for optimizing energy use, maintaining reliability, and supporting next-generation devices. With LINK-PP PoE RJ45 connectors, designers can ensure stable LLDP signaling, strong current endurance, and long-term network performance in every PoE application.  

1. What Is Power over Ethernet (PoE)?   Power over Ethernet (PoE) is a technology that allows both power and data to be transmitted through a single Ethernet cable. This eliminates the need for separate power supplies, simplifying installation, reducing costs, and enhancing network flexibility.   PoE technology is widely used in IP cameras, VoIP phones, wireless access points (WAPs), LED lighting, and industrial control systems.   Core concept: One cable — both power and data.     2. Evolution of PoE Standards   PoE technology is defined by the IEEE 802.3 standards and has evolved through several generations to support higher power delivery and wider applications.     Standard Common Name IEEE Release Year PSE Output Power PD Power Available Power Pairs Used Typical Cable Type Key Applications IEEE 802.3af PoE 2003 15.4 W 12.95 W 2 pairs Cat5 or higher VoIP phones, IP cameras, WAPs IEEE 802.3at PoE+ 2009 30 W 25.5 W 2 pairs Cat5 or higher PTZ cameras, thin clients IEEE 802.3bt PoE++ 2018 60–100 W 51–71 W 4 pairs Cat5e or higher Wi-Fi 6 APs, PoE lighting, industrial systems     Trend: Evolution of PoE Standards (IEEE 802.3af / at / bt) Increasing power output (15W → 30W → 90W) Transition from 2-pair to 4-pair power delivery Expansion to high-power, industrial, and IoT applications     3. Key Components of a PoE System   A PoE system consists of two essential devices:   PSE (Power Sourcing Equipment) — the device that provides power PD (Powered Device) — the device that receives power   3.1 PSE (Power Sourcing Equipment)   Definition: A PSE is the power source in a PoE network, such as a PoE switch (Endspan) or PoE injector (Midspan). It detects the presence of a PD, negotiates power requirements, and supplies DC voltage through Ethernet cables.   PSE Types:   Type Location Typical Device Advantage Endspan Built into PoE switches PoE switch Simplifies installation, fewer devices Midspan Between switch and PD PoE injector Adds PoE to existing non-PoE networks   3.2 PD (Powered Device)   Definition: A PD is any device powered through the Ethernet cable by a PSE.   Examples: IP cameras Wireless access points VoIP phones PoE LED lights Industrial IoT sensors   Characteristics: Classified by power levels (Class 0–8) Includes DC/DC conversion circuits Can dynamically communicate power needs (via LLDP)     4. PoE Power Delivery and Negotiation Process   The power delivery process follows a specific IEEE-defined sequence:   Detection: The PSE sends a low voltage (2.7–10V) to detect if a PD is connected. Classification: The PSE determines the PD’s power class (0–8). Power On: If compatible, PSE supplies 48–57V DC power to the PD. Power Maintenance: Continuous monitoring ensures power stability. Disconnection: If the PD disconnects or fails, the PSE cuts power immediately.     5. Role of LLDP in PoE Networks   LLDP (Link Layer Discovery Protocol) enhances PoE power management by enabling real-time communication between the PSE and PD. Through LLDP-MED extensions, PDs can dynamically report their actual power consumption, allowing the PSE to allocate energy more efficiently.   Benefits: Dynamic power allocation Better energy efficiency Reduced overload and heat issues   Example: A Wi-Fi 6 access point initially requests 10W, then dynamically increases to 45W during high traffic via LLDP communication.       6. Power over Ethernet Cable and Distance Considerations   Recommended maximum distance: 100 meters (328 feet) Cable requirement: Cat5 or higher (Cat5e/Cat6 preferred for PoE++) Voltage drop consideration: The longer the cable, the greater the power loss. Solution: For longer runs, use PoE extenders or fiber converters.     7. Common PoE Applications   Application Description Typical LINK-PP Product VoIP Phones Power and data via a single cable LPJK4071AGNL IP Cameras Simplified surveillance setup LPJG08001A4NL Wireless Access Points Enterprise and campus networks LPJK9493AHNL PoE Lighting Smart building and energy control LPJ6011BBNL Industrial Automation Sensors and controllers LPJG16413A4NL     8. LINK-PP PoE Solutions   LINK-PP offers a comprehensive range of PoE-compatible magnetic RJ45 connectors, integrated jacks, and transformers, all fully compliant with IEEE 802.3af/at/bt standards.     Highlighted Models:   Model Specification Features Applications LPJ0162GDNL.pdf 10/100 BASE-T, PoE 1500Vrms, LED indicators VoIP phones LPJK9493AHNL.pdf 10GBASE-T, IEEE 802.3bt PoE++ support, Up to 90W, low EMI High-performance APs     Related Resources: Understanding PoE Standards (802.3af / at / bt) Endspan vs. Midspan PSE in PoE Networks Role of LLDP in PoE Power Negotiation     9. Frequently Asked Questions (FAQ)   Q1: What is the maximum transmission distance of PoE? A: Up to 100 meters (328 ft) using Cat5e or higher cables. For longer distances, PoE extenders are recommended.   Q2: Can any Ethernet cable be used for PoE? A: Use at least Cat5 cable; Cat5e/Cat6 is recommended for PoE++.   Q3: How do I know if my device supports PoE? A: Check the specification sheet for “IEEE 802.3af/at/bt compliant” or “PoE supported.”   Q4: What happens if a non-PoE device is connected to a PoE port? A: PoE switches use a detection mechanism, so no power is sent unless a compliant PD is detected—safe for non-PoE devices.     10. Future of PoE Technology   PoE continues to evolve toward higher power levels (100W+), greater energy efficiency, and integration with smart building and IoT ecosystems. Emerging applications include PoE-powered lighting systems, networked sensors, and industrial robotics.   The combination of PoE++ (IEEE 802.3bt) and intelligent power management protocols, such as LLDP, makes it a cornerstone for the next generation of networked power systems.     11. Conclusion   Power over Ethernet (PoE) has transformed network infrastructure by delivering both data and power over a single cable. From small office deployments to industrial IoT systems, PoE simplifies installation, reduces cost, and enables smarter, more efficient connectivity.   With LINK-PP’s IEEE-compliant PoE magnetic connectors, engineers can design reliable, high-performance networks that meet modern power and data demands.