AN3213 datasheet(34/64 Pages) STMICROELECTRONICS

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ST7570 demonstration board description

AN3213

34/64

Doc ID 17429 Rev 1

The reasons for these characteristics can be described as follows:

●

The LV distribution network has a “tree” structure, with many branches and sub-

branches acting as parallel impedances

●

Several electronic devices connected to the LV network offer a very low impedance,

mostly because of the EMI input filters installed at their mains connection

●

The type and number of electronic loads connected to the mains network varies over

time

For all these reasons, particular attention must be paid to the impedance of the ST7570 line

coupling circuit. Specifically:

●

In receiving (idle) mode, the coupling impedance must be high enough to make the

power line source impedance negligible and to minimize the mutual interference

between different PLC nodes connected to the same network

●

In transmitting mode, the coupling impedance must be very low inside the signal

bandwidth but high enough for out-of-band frequencies.

According to these requirements, the EN50065-7 standard document fixes the following

constraints for the PLC node operating in the A band:

●

Tx mode:

–

free in the range 3 to 95 kHz

–3

Ω from 95 to 148.5 kHz

●

Rx mode:

–

Ω from 3 to 9 kHz

–

Ω between 9 and 95 kHz only inside the signal bandwidth (free for frequencies

outside the signal bandwidth)

–5

Ω from 95 to 148.5 kHz

Figure 26 and 27 show the input impedance magnitude vs. frequency measured in

transmission and reception mode.

The impedance magnitude values prove that the ST7570 demonstration board is compliant

with the EN50065-7 requirements. At the same time, the line interface gives an efficient

signal coupling both in transmission and reception.

AN3213 Datasheet(PDF) 34 Page - STMicroelectronics

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