AN3213 datasheet(54/64 Pages) STMICROELECTRONICS

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FAQs and troubleshooting

AN3213

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FAQs and troubleshooting

In this section the most frequently asked questions and the solution to common ST7570

demonstration board usage problems are described.

9.1

FAQs

●

Q: Is it possible to use ST power line transceivers on a medium or high voltage AC line?

–

A: Yes. The same circuit solution as for a low voltage AC line can be used,

provided that coupling interface (and particularly line transformer, power inductor

and Y2 capacitor) guarantees an adequate and safe isolation from the AC line.

●

Q: Is it possible to use the ST7570 on a DC or de-energized line?

–

A: No, the ST7570 device requires the 50-60 Hz zero crossing detection to work.

●

Q: Which kind of protocols can be used with the ST7570?

–

A: The embedded PHY and MAC protocol layers are mainly designed, but not

limited, to interface with a IEC61334-4-32 compliant Logic Link Control (LLC) layer

in applications targeting DLMS/COSEM, a widely-used European standard for the

application layer of meters.

●

Q: Does the ST7570 demonstration board meet FCC part 15 specs?

–

A: Yes. In fact, the EN50065 normative compliance intrinsically guarantees the

compliance with FCC part 15 regulations as well.

●

Q: What distance can a PLC signal cover?

–

A: Given a transmitted signal level of 2.5 V rms, at 1200 baud the ST7570 device

is able to transmit through a channel attenuating up to 84 dB. This means that in a

point-to-point link a distance of several km can be covered, according to the

characteristics of the line. Nevertheless, the allowable distance can be reduced

because of noisy devices and low-impedance loads connected on the power line;

such elements impact on the actual SNR seen by the receiver.

●

Q: Why with power line communication can I not get 100 % reachability even though

the range is a few meters?

–

A: A probability lower than 100 % to reach a PLC node within such a small

distance can depend on two main factors:

attenuation or losses on the power line (for example because of some heavy

capacitive load connected close to the transmitter)

noise coming from electric or electronic equipment connected on the power line

(for example SMPS, ballasts, or motors).

It can be useful to measure the signal level at transmitter and receiver to

understand if there are undesired losses. It is also important to measure the noise

level and spectral distribution to see whether the PLC channel is somehow

“jammed” by noise.

●

Q: Does the power line communication work if a power distribution transformer is

present between two nodes?

–

A: The communication could work, but the transformer impedance at the signal

frequency must be taken into account, as it could introduce strong attenuation in

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