Specifications

Chapter 6 – Design and Test for Electromagnetic Compatibility
186 PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Book
Introduction
Products that communicate using public ac mains wiring generally need to demonstrate compliance with
electromagnetic compatibility (EMC) standards from various regulatory agencies. This chapter provides information
regarding the most effective ways to satisfy electromagnetic interference (EMI) and electrostatic discharge (ESD)
requirements with Smart Transceiver-based products. For information regarding surge immunity refer to the discussion
at the end of Chapter 4.
Electromagnetic Interference (EMI) Compliance
In the USA, the FCC[1] requires that unintentional radiators comply with Part 15 level “B” for consumer and household
products and level “A” for industrial products. European countries generally require compliance to CENELEC
EN 50065-1[2]. Similar regulations are imposed in most countries throughout the world.
While it is the responsibility of each product developer to demonstrate compliance of their own product, the task is
greatly simplified by the availability of multiple Smart Transceiver reference layouts that have all been carefully
designed to pass the required regulations. Directly copying one of the eight PL Smart Transceiver layouts referenced in
Appendix A allows the product developer to proceed with the confidence that this same circuit layout has been verified
to meet the required regulations. Using one of the pre-verified power supply designs from Chapter 5 adds confidence
that an instance of this portion of the product has also been verified to satisfy regulatory requirements.
Most EMI sensitive circuitry is encapsulated in the PL Smart Transceiver reference layouts. Directly copying these
reference layouts greatly reduces the risk of EMI related issues. There are, however, a couple of sensitive circuit traces
that in some instances are either near the edge of a reference layout, or connect between the reference layout and the
coupling circuit. These traces need to be kept away from any high speed digital signals in order to preserve the proven
electromagnetic compatibility of the design. In no case should any circuit traces not associated with a reference layout
be run through the reference layout area. Digital or clock signals that operate at rates any higher than about 1kHz should
be placed >2mm from the edge of the reference layout if there is an intervening ground to act as a guard (or >10mm if
there is no intervening guard ground). The following is a list of reference circuit nets that should be isolated from
potential interference generating lines as described above:
TXOUT
RXIN
RXCOMP
TX2
TX3
XIN
XOUT
In addition to the specific recommendations above, good design practice dictates the use of a low inductance return path
for all signals (e.g., a ground plane) and the use of one or more power supply decoupling capacitors located next to each
integrated circuit.
If there are other aspects of product design for EMI compliance not associated with the PL Smart Transceiver that
require attention, the developer is encouraged to refer to the book, Noise Reduction Techniques in Electronic Systems
[11].