EMC Question of the Week: January 24, 2022

Differential Signal Transceiver

A device or circuit that implements the physical layer functions of the OSI model in a network interface controller is commonly called a

  1. PLT
  2. PLC
  3. PHY
  4. SerDes


The best answer is “c.” PHY is an abbreviation for "physical layer." It's often the last active IC encountered by a high-speed signal leaving a printed circuit board and the first encountered by an arriving signal. Some PHYs (e.g., USB) are typically embedded in a microcontroller. Ethernet PHYs are usually external to the controller in their own package.

Because they operate at very high speeds and because they are an important interface to circuits and systems off the board, the location and layout of Ethernet PHYs play an important role in ensuring EMC compliance.

The other options are clearly incorrect. PLT is an acronym more commonly associated with power line transients. PLC is an acronym for "programmable logic controller." SerDes (short for Serializer/Deserializer) devices convert digital data between serial and parallel interfaces. 

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