AN3213
Application note
ST7570 S-FSK power line networking system-on-chip
design guide for AMR
Introduction
The ST7570 demonstration board has been realized as a useful tool which exploits the
performance capability of the ST7570 S-FSK power line networking system-on-chip
(References
1).
With this demonstration board, it is possible to evaluate the ST7570 features and its
transmitting and receiving performance directly on the power line.
The coupling interface is designed to allow the ST7570 device to transmit and receive on the
mains using a spread-spectrum FSK signal with 63.3 and 74 kHz tone frequencies, within
the European CENELEC EN50065-1 standard A-band, specified for automatic meter
reading (References
4).
Figure 1.
ST7570 demonstration board with outline dimensions
As can be seen from
Figure 1,
special effort has been made to make the demonstration
board as compact as possible, while including all the features which enable the ST7570 to
perform at its best.
Note:
The information provided in this application note refers to the EVALST7570-1 demonstration
board.
October 2010
Doc ID 17429 Rev 1
1/64
www.st.com
Contents
AN3213
Contents
1
2
3
4
5
6
7
Abbreviations used in this document . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Safety recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ST7570 S-FSK power line networking system-on-chip description . . 12
Demonstration tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Test and measurement tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
ST7570 demonstration board description . . . . . . . . . . . . . . . . . . . . . . 15
7.1
Line coupling section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.1.1
7.1.2
7.1.3
7.1.4
7.1.5
Transmission active filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Reception passive filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Power line coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Zero crossing coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Input impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.2
Conducted disturbances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.2.1
7.2.2
7.2.3
7.2.4
Conducted emission (CE) measurements . . . . . . . . . . . . . . . . . . . . . . . 35
Noise immunity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
AWGN tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
NBI tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
7.3
PCB layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
7.3.1
7.3.2
7.3.3
Thermal performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Ground connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
7.4
7.5
7.6
7.7
Thermal impedance and power dissipation calculation . . . . . . . . . . . . . . 43
Oscillator section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Surge and burst protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8
Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
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8.1
8.2
Three-phase architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Received signal strength indication (RSSI) . . . . . . . . . . . . . . . . . . . . . . . 51
9
FAQs and troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
9.1
9.2
FAQs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
10
11
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Appendix A Board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
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List of tables
AN3213
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Electrical and thermal characteristics of the ST7570 demonstration board . . . . . . . . . . . . . 8
TX_OUT level vs. TX_GAIN - typical values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
BOM list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
ST parts on board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Line coupling transformer specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Noise level SN0 and SN1 during AWGN tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Narrow-band interferer immunity test settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
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List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
ST7570 demonstration board with outline dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
I(VCC) vs. I(PA_OUT) curve - typical values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
ST7570 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Board drawing with indication of the various sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Global view of the ST7570 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
ST7570 schematic circuit (part 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Power supply section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
UART interface section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
External microcontroller connection section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
ST7570 schematic circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Reset circuit section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
JTAG lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Current limit setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Non-isolated zero crossing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
USB to UART connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Reception and transmission filter schematics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Measured frequency response of the transmission active filter (typical) . . . . . . . . . . . . . . 27
Montecarlo simulation of the transmission active filter frequency response . . . . . . . . . . . . 28
Measured frequency response of the reception passive filter (typical) . . . . . . . . . . . . . . . . 29
Montecarlo simulation of the reception passive filter response . . . . . . . . . . . . . . . . . . . . . 30
Measured frequency response of the Tx active + passive filter loaded with the EN50065-1
LISN impedance (typical) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Montecarlo simulation of the transmission line coupling response loaded with the
EN50065-1 LISN impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Non-isolated zero crossing coupling circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
ZC_IN_A vs. mains voltage - delay measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
ZC_IN_A vs. mains voltage - jitter measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Measured input impedance modulus of the line coupling - reception mode (typical) . . . . . 35
Measured input impedance modulus of the line coupling - transmission mode (typical) . . 35
Conducted emissions test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Conducted emissions: transmission spectrum, quasi-peak measurement, 3 kHz - 150 kHz,
line-to-earth, as per EN50065-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Conducted emissions: transmission spectrum, quasi-peak measurement, 3 kHz - 150 kHz,
neutral-to-earth, as per EN50065-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Conducted emissions: transmission spectrum, quasi-peak measurement, 150 kHz - 30 MHz,
line-to-earth, as per EN50065-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Conducted emissions: transmission spectrum, quasi-peak measurement, 150 kHz - 30 MHz,
neutral-to-earth, as per EN50065-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Noise immunity test setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Measured BER vs. SNR curve (typical), white noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Example of stencil openings for the QFN48 package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
PCB copper dissipating area on top layer for the ST7570 demonstration board . . . . . . . . 42
PCB copper dissipating area on bottom layer for the ST7570 demonstration board . . . . . 42
Packet-fragmented transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Measured ST7570 thermal impedance curve (typical) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Simulation model of the thermal impedance ZthJA of the ST7570 mounted on the
demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Carrier frequency deviation vs. crystal tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Doc ID 17429 Rev 1
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