ST8500
Device architecture
2.1.1
Digital front-end (DFE)
Transmission and reception filter chains
The DFE includes programmable transmission/reception digital filter chains to fit the signal
bandwidth in different PLC modulation cases. The ADC and DAC clock frequencies are
controlled by the DFE to get the right sample rate fitting the filter chain configuration.
Automatic gain control (AGC)
The DFE implements the automatic gain control (AGC) block for the PGA, whose purpose is
to adapt the signal to the ADC dynamic range.
2.1.2
Analog front-end (AFE)
Reception chain
The ST8500 AFE features a programmable gain amplifier (PGA) and a dedicated analog-to-
digital converter (ADC) to achieve high RX sensitivity and a wide input range.
Transmission chain
The transmitted signal, generated in the digital domain, is fed into a dedicated digital-to-
analog converter (DAC).
The DAC output is then fed into a pre-driver for buffering and applying an additional gain.
Zero crossing comparator
The mains line zero crossing can be detected by providing a mains synchronous bipolar
(AC) signal at the input of this comparator.
The zero crossing comparator provides positive and negative event information
(rising/falling edge or high/low level).
Zero crossing information can also trigger an event for the GPT0 timer in order to capture
the zero crossing timestamp for the application purpose.
Line driver thermal sense
The AFE also includes the thermal sense (TS) block to detect the temperature of the line
driver.
Line driver current sense
The AFE also includes the current sense (CS) block to detect the output current of the line
driver.
2.1.3
Real-time engine (RTE)
To effectively and flexibly target the performance required by different PLC standards, the
ST8500 embeds a dedicated high performance fully programmable real-time engine (RTE).
It is able to address specific real-time PLC functionalities such as modulation and
demodulation according to different modulation schemes, advanced correction coding
algorithms (Viterbi, Convolutional, Reed-Solomon, etc.) and several other time-constrained
communication services.
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