AN4068 datasheet(53/63 Pages) STMICROELECTRONICS

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AN4068

FAQs and troubleshooting

Doc ID 022923 Rev 2

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FAQs and troubleshooting

In this section the most frequently asked questions and solutions to common ST7580

reference design usage problems are described.

11.1

FAQs

●

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

–

A: Yes. The same circuit solution as for low-voltage AC lines can be used, provided

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

the X1 capacitor) guarantees an adequate and safe isolation from the AC line.

●

Q: Is it possible to use the ST7580 on a DC or de-energized line?

–

A: Yes. The ST7580 can communicate over any wired connection, given that a

suitable coupling circuit is used to connect the device to the line.

●

Q: Which kinds of protocols can be used with the ST7580?

–

A: The ST7580 device has been conceived as an open protocol device and can be

used according to the application needs. The user can develop their own protocol

or use a standard one.

●

Q: Does the ST7580 reference design meet FCC part 15 specs?

–

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

compliance with FCC part 15 regulations as well.

●

Q: What distance can be covered with a PLC signal?

–

A: Given a transmitted signal level of 2.5 V rms, in PSK mode the ST7580 device

is able to transmit through a channel attenuating up to 86 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 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, motors).

It may 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 find out 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 may work, but the transformer impedance at the signal

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

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