To shorten the line length between the network transformer and the RJ45 interface, make the PCB layout more compact, reduce signal transmission loss, and enhance anti-interference capability, Leiditech has launched an integrated network transformer interface and the corresponding electrostatic surge protection solution. The integrated network transformer interface supplied by Leiditech, part number FC62115BNL-LM, is matched with the anti-static component ULC332010T8 in the scheme shown in the figure below. It has strong electrostatic surge protection reliability and meets IEC61000-4-2, Level 4, contact discharge 30kV, air discharge 30kV; IEC61000-4-5 20A (8/20μs).

Protection Solution Reference Design:

Introduction of Solution Design

1.       Primary side:       

The primary side of the network transformer is respectively connected to the differential pairs of TD and RD. When PCB routing, the line sequences of the two sets of differential pairs can be exchanged.

•ESD protection: The differential correspondence between TD and RD first connects the electrostatic protection device to effectively protect the back-end PHY chip.

•VCC power supply and decoupling capacitor: For current-type PHY, the primary coil needs to be connected to the VCC of the PHY and then connected to GND through a 100nF capacitor. For voltage-type phy, only the primary tap needs to be connected to the 100nF capacitor and grounded to filter out high-frequency noise. It is recommended to parallel two 49.9Ω resistors in the middle of each differential pair near the chip pins and connect them to GND.

2. Secondary side:

The secondary side is equipped with J1, J2, J3, and J6 pins that have been connected to the RJ45 interface. And it integrates the BOB Smith circuit, effectively protecting against lightning surges;

2.       Grounding treatment:

It is recommended that the ground of the casing and the ground of the circuit be connected in parallel through a 1nF/2000V ceramic capacitor and a 10MΩ resistor. The fixed pins of the RJ45 interface should also be connected to the ground of the casing and eventually flow into the ground to ensure the integrity of the grounding system of the entire circuit.

Parameters for Part Number Selection:

Leiditech also launched 100-megabit and 1-gigabit network transformers for discrete devices to meet the diverse requirements of different customers. The following are the corresponding protection solutions for your reference:

Reference Solution for Lightning Protection and Electrostatic surge Protection of 100 Megabit Network ports:

Reference Solution for Lightning Protection and Electrostatic surge Protection of 1000 Megabit Network ports:

Part Number Parameters for Protection Diagram Selection:

The above discrete device protection solution is suitable for lightning protection and electrostatic surge protection of network ports. It applies two-level protection, has strong reliability, can ensure signal integrity, and meets IEC61000-4-2, level 4, contact discharge 30kV, air discharge 30kV. Iec 61000-4-5 10/700μs, 40Ω, 6kV, ±5 times.