Protecting Ethernet lines from surges and electrostatic discharge (ESD) is crucial to prevent damage to sensitive equipment. Let’s address your questions one by one:
- Effect of Diode Speed: You are correct that the 1.5KE6.8A diode is extremely fast with a response time of less than 1 nanosecond. The HER107 diodes, with a response time of 70 nanoseconds, are considerably slower in comparison. In surge protection circuits, faster response times are generally better, as they can more effectively clamp the voltage before it reaches harmful levels. When an ESD event occurs, the voltage can rise very quickly, and having a faster response time can be critical to providing effective protection.
- Series Diodes: When you connect diodes in series, their forward voltage drops add up, and their reverse recovery times do not. In other words, the resultant response time of the circuit will not be improved by connecting diodes in series. Instead, the total forward voltage drop across the diodes will increase, which can affect the signal integrity of the Ethernet line.
- Use of Schottky Diodes: Schottky diodes are known for their fast switching speed, typically in the range of nanoseconds. If you need faster response times for surge protection in Ethernet lines, using Schottky diodes with a response time of 5 nanoseconds or less would be a better choice than the HER107 diodes. However, be aware that Schottky diodes have a lower reverse breakdown voltage compared to Zener diodes like the 1.5KE6.8A. You should select Schottky diodes with a voltage rating that matches the requirements of your Ethernet circuit.
In summary, for optimal surge protection in Ethernet lines, it’s advisable to use diodes with faster response times, such as Schottky diodes, to ensure effective clamping of voltage spikes during ESD events. Be sure to select diodes with appropriate voltage and current ratings for your specific application, and consider other surge protection components like transient voltage suppressors (TVS) and gas discharge tubes (GDTs) as part of a comprehensive protection strategy, especially in environments where surge events are common.