Tel-Notes Detail Effective ONT and Server Protection Solutions

There’s no patience with communications equipment downtime as consumers continue to demand the highest reliability connectivity and service.  So, it stands to reason that adding circuit protection to almost all equipment designs is a necessary requirement to support reliable 24/7 operation.

For example, servers and network equipment commonly implement add-in or hot-swappable cards that enable individual components to be added or replaced without the need to stop or shut down the system. One issue that can arise during a plug/unplug event is that the hot-swap controller interrupts the current flow. This can cause the card’s high di/dt and input inductance to generate a high-voltage surge, which can easily exceed twice the supply voltage. That’s why it is vital to account for the transient voltage the hot-swap controller will experience with a proven overvoltage and overcurrent protection solution.

Another application that requires protection is Fiber to the Home (FTTH). To provide consumers with streaming video and other video programming, many Telco providers are installing FTTH. In Consumer Premises Equipment (CPE), the fiber is terminated with an Optical Network Terminal (ONT) that is typically placed in an out-of-the-way place in a home or office and powered by the customer. The ONT box converts the optical signal in the fiber to an electrical signal, and because of its remote location, it must be well-protected from electrical line disturbances. The ONT box is also required to comply with all local surge requirements specified by standards that include ITU-T, IEC and GR-1089. The downside is that adding surge protection increases the cost and size of the ONT. Therefore, designers frequently must make critical trade-off decisions between the protection level afforded in the product and the acceptable size and cost of the ONT solution.

Providing answers to these challenges, Bourns has recently posted two Tel-Notes that outline effective protection solutions for ONT and Server Power Bus applications. These helpful design resources detail the optimal combination of components for the job that include:

  • For the Server Power Bus, a TVS diode with a power rating larger than the surge energy is required at the input to absorb the inductive surge.
  • Protection for one of the ONT ports, the Ethernet PHY within the Ethernet port, is commonly achieved by an isolated transformer and PHY-side TVS diode array with a high peak pulse rating (Ipp) and low clamping voltage (Vc).

In the Tel-Notes, you will learn more about Bourns’ extensive portfolio of sensing and circuit protection products that keep sensitive downstream components in a blade or hot-swappable card safe against damaging surges up to rated device limits.

Also covered are the features that make our latest Chip LAN transformer a higher reliability solution. See why its consistent machine-wound and low-profile design that offers the same isolation level as traditional LAN transformers are true benefits for space-constrained ONT applications.

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