Powerline communications (PLC) has
been available for many years, but it
hasn’t always lived up to its expectations.
Electrical utilities regularly use the
technology to monitor and control ac
power lines. Some companies have even
tried offering broadband Internet services.
But the high-speed limitations of the
ac lines as well as noise and interference
issues have impeded its progress.
Still, designers can use PLC for monitoring
and control functions at low data rates, like automatic meter reading,
energy management, and home automation.
Maxim’s MAX2990 single-chip
powerline modem not only targets these
applications, it also provides exceptional
data rates, reliability, and performance
over long powerline runs (see the figure).
The MAX2990 uses orthogonal frequency-
division multiplexing (OFDM)
with differential binary phase-shift
keying (DBPSK) and forward error
correction (FEC) to provide reliable
data transfers in the presence of
noise, narrowband interferers,
group delays, jammer
signals, impulse noise,
and frequency selective
attenuations.
Additionally, it operates
from 10 kHz to 490
kHz and can achieve up
to 100 kbits/s. The chip
complies with powerline
signaling regulations from
CENELEC, the Federal Communications
Commission (FCC), and the
Association of Radio Industries and
Businesses (ARIB) as well.
Advanced channel-coding methods
such as Reed Solomon FEC and convolutional
encoding give the MAX2990
its superior performance. These errorcorrecting
codes are transmitted with the
data on different OFDM tones within
the band to maximize the chip’s datarecovery
ability. As a result, it delivers
a typical bit-error rate (BER)
of 10–4 with a signal-tonoise
ratio (SNR) of –4 dB at 32 kbits/s
between 10 and 95 kHz.
A fast Data Encryption Standard
(DES) engine serves as an encryption/
decryption coprocessor for very secure
transmissions. When used in a network
with many nodes, it employs the
CDMA/CA channel access arbitration
method and automatic repeat request
(ARQ) to ensure reliable packet delivery.
The MAX2990 packages the physical
layer (PHY) and media access control
(MAC) layer in a single chip that additionally
integrates Maxim’s 16-bit RISC
MAXQ microcontroller. It includes 32
kbytes of flash to run the MAC code and
user-defined application, as well as 8
kbytes of SRAM for data storage.
The chip also offers includes UART,
SPI, and I2C serial interfaces. A real-time
clock is included, along with a set of
pulse-width modulation (PWM) counters
for applications such as LED brightness
control.
