Intermittent noise sources, impedance changes, and attenuation make the power line
a hostile signal path. The PLT-22 transceiver operates reliably in this harsh
environment through a novel dual carrier frequency capability as well as custom
digital signal processing which provides adaptive carrier and data correlation,
impulse noise cancellation, tone rejection, and low-overhead error correction. These
innovations permit the transceiver to operate reliably in the presence of consumer
electronics, power line intercoms, motor noise, electronic ballasts, dimmers, and
other typical sources of interference.
Each PLT-22 transceiver operates as a backward compatible replacement for the
PLT-20 and PLT-21 transceivers when used with previous versions of configuration
parameters. In this mode, all transmissions can be received by any PLT-20, PLT-21,
or PLT-22 transceiver.
When used with new transceiver configuration parameters, the dual carrier
frequency mode of the PLT-22 transceiver is activated. In this mode, PLT-22 based-
nodes are able to communicate even when the primary frequency range (125kHz -
140kHz) is blocked by noise. With dual frequency mode, a PLT-22 transceiver begins
each transaction by sending backward compatible packets. If impairments prevent
communication in this frequency range, the PLT-22 node will automatically switch
carrier frequencies in order to complete the transaction with other PLT-22 based
nodes.
The PLT-22 transceiver complies with FCC, Industry Canada, Japan MPT, and
European CENELEC EN 50065-11regulations for signaling in the 125kHz-to-
140kHz and 95kHz-to-125 kHz frequency bands. The transceiver implements the
CENELEC access protocol, which can be enabled or disabled by the user. By
incorporating the access protocol into the power line transceiver, Echelon has
eliminated the need for users to independently develop the complex timing and
access algorithms mandated by the CENELEC EN 50065-1 regulation. The PLT-22
transceiver also is compliant with the Electronic Industries Association Standard
EIA-709.2.
The transceiver's power amplifier includes a selectable 3.5V peak-to-peak (p-p) or 7V
p-p mode for maximum communication performance. The 1Ωoutput impedance and
1A p-p current capability of the amplifier allow it to drive high output levels into low
impedance circuits, while the highly efficient design draws less total current than
previous transceivers.
The PLT-22 transceiver is powered by user-supplied +8.5 to +16VDC and +5VDC
power supplies. The wide supply range is a key benefit when designing inexpensive
power supplies. If a battery-backed power supply is used, the transceiver will
continue signaling even during a power failure on the power mains.
The PLT-22 transceiver incorporates a power management feature that constantly
monitors the status of the node's power supply. If during transmission the power
supply voltage falls to a level that is insufficient to ensure reliable signaling, the
transceiver tells the Neuron Chip to stop transmitting until the power supply voltage
rises to an acceptable level. This allows the use of a power supply with 1/3 the
current capacity otherwise required (100mA versus 300mA). The net result is a
reduction in the size, cost, and thermal dissipation of the power supply. Power
management is especially useful for high volume, low cost consumer products such as
electrical switches, outlets, and dimmers.
1-2 Introduction
