ST ST7538Q Installation and operating instructions

April 2008 Rev 1 1/56
56
AN2744
Application note
ST7538Q power line FSK transceiver
dual channel reference design for AMR
Introduction
The ST7538Q dual channel reference design is a practical tool to start the activity of
designing an automatic meter reading (AMR) node based on the ST7538Q power line FSK
transceiver.
With this reference design, it is possible to evaluate the features of the ST7538Q and its
transmitting and receiving performances in an actual communication on the power line
network.
The ST7538Q reference design can be considered as composed of three main sections:
■power supply section, specifically designed to coexist with power line communication and
to operate from a wide-range input mains voltage
■modem and crystal oscillator section
■dual channel line coupling interface section
The dual channel line coupling interface allows the ST7538Q FSK transceiver to transmit
and receive on the mains using two different carrier frequencies: 72 kHz and 86 kHz, both
within the frequency band A specified by the European CENELEC EN50065 standard for
AMR applications.
Figure 1. ST7538Q dual channel reference design board with outline dimensions
As it can be seen from the picture above, a special effort has been made to develop a
compact reference design board, oriented to practical applications.
Note: The information provided in this application note refers to the EVALST7538DUAL reference
design board.
56mm
98mm
www.st.com

Contents AN2744
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Contents
1 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Safety precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 ST7538Q FSK power line transceiver description . . . . . . . . . . . . . . . . 10
4 Evaluation tools description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1 Line coupling interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.1.1 Dual channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1.2 Dual channel Tx passive filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1.3 Dual channel Rx passive filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.1.4 Dual channel Rx active filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.1.5 Input impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.2 Conducted disturbances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2.1 Conducted emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2.2 Noise immunity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.3 Thermal design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.4 Oscillator section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.5 Surge and burst protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.6 50-pin connector for communication board . . . . . . . . . . . . . . . . . . . . . . . 40
5.7 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6 Performance and ping tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
7 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.1 Three-phase architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.2 Received signal strength indication (RSSI) . . . . . . . . . . . . . . . . . . . . . . . 47
7.3 110-132.5 kHz dual channel coupling circuit . . . . . . . . . . . . . . . . . . . . . . 49
8 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
9 List of normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

AN2744 Contents
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Appendix A Board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

List of figures AN2744
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List of figures
Figure 1. ST7538Q dual channel reference design board with outline dimensions. . . . . . . . . . . . . . . 1
Figure 2. Typical curve for output current limit vs. RCL value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 3. ST7538Q transceiver block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 4. Complete evaluation system including a PC, an EVALCOMMBOARD and the
EVALST7538DUAL board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 5. Power line modem demonstration kit with transmission session window . . . . . . . . . . . . . . 13
Figure 6. Scheme of the various sections of the board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 7. Modem and coupling interface schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 8. Power supply schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 9. Schematic of Rx and Tx filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 10. Measured frequency response of the Tx passive filter for 72 kHz channel (typical). . . . . . 22
Figure 11. Measured frequency response of the Tx passive filter for 86 kHz channel (typical). . . . . . 23
Figure 12. Simulated frequency response of the Tx passive filter for 72 kHz channel with tolerance
effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 13. Simulated frequency response of the Tx passive filter for 86 kHz channel with tolerance
effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Figure 14. Measured frequency response of the Rx passive filter for 72 kHz channel (typical) . . . . . 25
Figure 15. Measured frequency response of the Rx passive filter for 86 kHz channel (typical) . . . . . 26
Figure 16. Simulated frequency response of the Rx passive filter for 72 kHz channel with tolerance
effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 17. Simulated frequency response of the Rx passive filter for 86 kHz channel with tolerance
effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 18. Measured frequency response of the Rx active filter for 72 kHz channel (typical) . . . . . . . 27
Figure 19. Measured frequency response of the Rx active filter for 86 kHz channel (typical) . . . . . . . 28
Figure 20. Simulated frequency response of the Rx active filter for 72 kHz channel with tolerance
effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 21. Simulated frequency response of the Rx active filter for 86 kHz channel with tolerance
effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 22. Measured input impedance magnitude of the coupling interface in Rx mode for the 72 kHz
channel (typical curve) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 23. Measured input impedance magnitude of the coupling interface in Rx mode for the 86 kHz
channel (typical curve) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 24. Measured input impedance magnitude of the coupling interface in Tx mode for the 72 kHz
channel (typical curve) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 25. Measured input impedance magnitude of the coupling interface in Tx mode for the 86 kHz
channel (typical curve) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 26. Conducted disturbance test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 27. Output spectrum (typical) at 72 kHz channel, mains 220 VAC, fixed transmitted
tone = "1" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 28. Output spectrum (typical) at 86 kHz channel, mains 220 VAC, fixed transmitted
tone = "1" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 29. Narrowband conducted interference test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 30. Measured BER vs. SNR curve (typical), white noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Figure 31. Measured SNR vs. frequency curves (typical) at BER=10-3 - 72 kHz channel . . . . . . . . . 35
Figure 32. Measured SNR vs. frequency curves (typical) at BER=10-3 - 86 kHz channel . . . . . . . . . 35
Figure 33. PCB copper dissipating area for the ST7538Q dual channel reference design . . . . . . . . . 36
Figure 34. Packet-fragmented transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Figure 35. Thermal impedance typical curve for the ST7538Q mounted on the reference design
board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Figure 36. A recommended oscillator section layout for noise shielding . . . . . . . . . . . . . . . . . . . . . . . 38

AN2744 List of figures
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Figure 37. Common mode disturbances protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Figure 38. Differential mode disturbances protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Figure 39. Scheme of the communication board connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Figure 40. Typical waveforms at 230 VAC: open load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Figure 41. Typical waveforms at 230 VAC: full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Figure 42. Typical waveforms at 265 VAC: short-circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Figure 43. Typical waveforms at 265 VAC: startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Figure 44. Load regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Figure 45. SMPS efficiency curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Figure 46. Demonstration software window for the master board . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Figure 47. Scheme of principle for three-phase architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Figure 48. Peak detector electrical schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Figure 49. Measured DC_OUT vs. AC_IN peak detector performance . . . . . . . . . . . . . . . . . . . . . . . . 48
Figure 50. PCB layout - top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Figure 51. PCB layout - bottom view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

List of tables AN2744
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List of tables
Table 1. Electrical characteristics of the ST7538Q dual channel reference design . . . . . . . . . . . . . . 7
Table 2. Output signal level setting through VSENSE partitioning - typical values . . . . . . . . . . . . . . . . 8
Table 3. Bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 4. ST parts on the ST7538Q dual channel reference design board . . . . . . . . . . . . . . . . . . . . 19
Table 5. Line coupling transformer specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 6. Noise immunity test settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Table 7. 50-pin connector digital signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Table 8. 50-pin connector control signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table 9. 50-pin connector power connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table 10. SMPS specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table 11. SMPS transformer specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 12. List of components to be modified for the 110-132.5 kHz dual channel coupling. . . . . . . . 49
Table 13. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

AN2744 Electrical characteristics
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1 Electrical characteristics
Table 1. Electrical characteristics of the ST7538Q dual channel reference design
Parameter Value Notes
Min. Typ. Max.
Operating condition
Ambient operating
temperature 85 °C
If junction temperature
exceeds 180 °C the device
shuts down
Transceiver section
Selectable channel frequencies: 72 kHz (CH1), 86 kHz (CH2)
Transmitting specifications (Tx Mode)
Transmitting output voltage
level 2 VRMS 2.25 VRMS
R20 = 3.9 kΩ, R22=2.2 kΩ
– see Ta b le 2
Transmitting output current
limit 325 mARMS R19 = 2 kΩ– see Figure 2
Second harmonic distortion -55 dB Loaded with CISPR 16-1
network
Third harmonic distortion -61 dB Loaded with CISPR 16-1
network
50 Hz attenuation 100 dB
Receiving specifications (Rx Mode)
Minimum detectable Rx signal 53 dB/µVRMS BER<10-3, negligible noise
Auxiliary supply
5 V linear regulator (VDC)
output voltage -5% 5.05 V +5% ST7538Q internally generated
5 V linear regulator (VDC)
current capability 100 mA
Power supply section
AC mains voltage range 85 V 265 V
Mains frequency 50-60 Hz
Output voltage -10% 10 V +10% Green LED ON
Output voltage ripple 1% IOUT = 600 mA, VIN=85 VAC
Output current 600 mA
Output power 5.6 W
Efficiency at POUT = 3.5 W 70%
Nominal transformer
isolation(1) 4 kV Primary to secondary/ secondary to auxiliary
Number of holdup cycles 0

Electrical characteristics AN2744
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Note: 1 EN50065-1 normative compliance is not guaranteed with a signal level at mains output
greater than 2 VRMS
Parameter Value Notes
Input power 100 mW
Switching frequency -10% 60 kHz +10% Transceiver section in Tx mode
1. ST does not guarantee transformer isolation. ST assumes no responsibility for the consequences that may result from that
risk.
Table 1. Electrical characteristics of the ST7538Q dual channel reference design (continued)
Table 2. Output signal level setting through VSENSE partitioning - typical values
VOUT [VRMS]V
OUT [dBuVRMS](R 7+ R8) / R8R7[kΩ]R 8[kΩ]
1.000 120 1.25 0.910 2.2
1.125 121 1.4 1.3 2.2
1.250 122 1.6 2.2 2.2
1.500 124 2.0 2.7 2.2
1.800 125 2.25 3.3 2.2
2.000 126 2.5 3.9 2.2
2.250 (Note 1) 127 2.8 4.7 2.2
2.500 (Note 1) 128 3.15 6.8 2.2
3.000 (Note 1) 130 4.0 7.5 2.2
Figure 2. Typical curve for output current limit vs. RCL value
100
150
200
250
300
350
400
1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5
Rcl (kOhm)
Irms (mA)
100
150
200
250
300
350
400
1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5
Rcl (kOhm)
Irms (mA)

AN2744 Safety precautions
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2 Safety precautions
The board must be used only by expert technicians. Due to the high voltage (220 V ac)
present on the parts which are not isolated, special care should be taken with regard to
people's safety.
There is no protection against high voltage accidental human contact.
After disconnection of the board from the mains, none of the live parts should be touched
immediately because of the energized capacitors.
It is mandatory to use a mains insulation transformer to perform any tests on the high
voltage sections (see circuit sections highlighted in Figure 7 and Figure 8) in which test
instruments like spectrum analyzers or oscilloscopes are used.
Do not connect any oscilloscope probes to high voltage sections in order to avoid damaging
instruments and demonstration tools.
Warning: ST assumes no responsibility for any consequences which
may result from the improper use of this tool.

ST7538Q FSK power line transceiver description AN2744
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3 ST7538Q FSK power line transceiver description
The ST7538Q transceiver performs a half-duplex communication over the power line
network using frequency shift keying (FSK) modulation. It operates from a 7.5 to 12.5 V
single supply voltage (PAVCC) and integrates a differential-output power line interface (PLI)
stage and two linear regulators providing 5 V (VDC) and 3.3 V (DVDD).
The ST7538Q can be programmed to communicate using eight different frequency
channels (60, 66, 72, 76, 82.05, 86, 110 and 132.5 kHz), four baud rates (600, 1200, 2400
and 4800 symbols per second) and two frequency deviations (1 and 0.5).
Many auxiliary functions are integrated. The transmission section includes automatic control
on PLI output voltage and current, programmable time-out function and thermal shutdown.
The reception section includes automatic input level control, carrier/preamble detection and
band-in-use signaling.
Additional features are included, such as watchdog timer, zero-crossing detector, internal
oscillator and a general purpose op-amp.
The serial interface (configurable as UART or SPI) allows interfacing to a host
microcontroller, intended to manage the communication protocol. A reset output (RSTO)
and a programmable 4-8-16 MHz clock (MCLK) can be provided to the microcontroller to
simplify the application.
Communication on the power line can be either synchronous or asynchronous with the data
clock (CLR/T) provided by the transceiver at the programmed baud rate.
When in transmission mode (i.e. RxTx line at low level), the ST7538Q transceiver samples
the data on the TxD line, generating an FSK modulated signal on the ATO pin. The same
Figure 3. ST7538Q transceiver block diagram

AN2744 ST7538Q FSK power line transceiver description
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signal is fed into the differential power amplifier to get four times the voltage swing and a
current capability up to 370 mA rms.
When in reception mode (i.e. RxTx line at high level), an incoming signal at the RAI line is
demodulated and converted to a digital bit stream on the RxD pin.
The internal control register, which contains the operating parameters of the ST7538Q
transceiver, can be programmed only using the SPI interface. The control register settings
include the header recognition and frame length count functions, which can be used to apply
byte and frame synchronization to the received messages.

Evaluation tools description AN2744
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4 Evaluation tools description
The complete evaluation environment for the ST7538Q power line communication consists
of:
– 1 PC using the "ST7538 power line modem demonstration kit" software tool
– 1 EVALCOMMBOARD hosting an ST7 microcontroller
– 1 ST7538Q dual channel reference design board (EVALST7538DUAL)
The correct procedure for connecting the EVALST7538DUAL and the EVALCOMMBOARD
is as follows:
1. Connect the EVALST7538DUAL and the EVALCOMMBOARD together
2. Connect the ac cable to the EVALST7538DUAL and the USB cable to the
EVALCOMMBOARD
3. Connect the EVALST7538DUAL to the mains supply
4. Connect the EVALCOMMBOARD to the PC via USB cable
Warning: Follow the connection procedure to avoid damaging the
boards!
Figure 4. Complete evaluation system including a PC, an EVALCOMMBOARD and the
EVALST7538DUAL board
USB/RS232USB/RS232

AN2744 Evaluation tools description
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This complete communication node, controlled by the ST7538Q power line modem
demonstration kit, implements real communication at bit level, simply sending or receiving a
user-defined bit stream.
It is possible to establish a half-duplex communication between two of these communication
nodes connected to each other. For better evaluating communication performances, the
ST7538Q power line modem demo kit software tool has some particular features, including:
●Frame synchronization: a frame synchronization header can be added to the
transmitted data to set up a simple protocol, intended to test the capability of the
system to correctly receive the exact bit sequence as it has been transmitted. This
feature can be enabled in the Rx panel of the ST7538Q power line modem
demonstration kit. A bit synchronization can be introduced as a simpler feature by
enabling the preamble detection method in the control register panel and then inserting
at least one "0101" or "1010" sequence at the beginning of the bit stream to be
transmitted.
●Ping session: a master-slave communication with automatic statistics calculation can
be useful to test a point-to-point or a point-to-multipoint power line communication
network, thus providing a method to evaluate reachability of each node in the network.
For further details about the ST7538Q power line modem demonstration kit tool, please
refer to user manual UM0241 "ST7538 power line modem demonstration kit graphical user
interface”.
Figure 5. Power line modem demonstration kit with transmission session window

Board description AN2744
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5 Board description
The ST7538Q dual channel reference design is composed of the following sections:
– power supply section, based on ST’s VIPer12A-E IC
– ST7538Q modem and crystal oscillator section
– line coupling interface section, with three subsections:
– dual channel transmission passive filter
– dual channel reception passive filter
– dual channel reception active filter
The board has also two connectors, which allow the user to plug the mains supply on one
side of the board and the IBU communication board on the other side.
The schematics of the whole reference design are given in the following pages. Figure 7
shows the modem and coupling interface circuits, while Figure 8 represents the power
supply circuit. In both schematics, high voltage regions are highlighted.
Table 3 lists the components used to develop the reference design board. All parts have
been selected to give optimal performances.
The layout of the printed circuit is shown in Appendix A - Figure 50 and Figure 51.
Figure 6. Scheme of the various sections of the board
ST7538Q
Modem
Section
ST7538Q
ST7538Q
Modem
Modem
Section
Section
Dual Channel
TX Passive
Filter
Dual Channel
Dual Channel
TX Passive
TX Passive
Filter
Filter
Dual Channel
RX Passive Filter
Dual Channel
Dual Channel
RX Passive Filter
RX Passive Filter
Dual Channel
RX Active Filter
Dual Channel
Dual Channel
RX Active Filter
RX Active Filter
Power Supply
(with ST Viper 12A)
Power Supply
Power Supply
(with ST Viper 12A)
(with ST Viper 12A)
Connection to
Connection to µ
µC Board
C Board
Connection to
Connection to
Mains Supply
Mains Supply
ST7538Q
Modem
Section
ST7538Q
ST7538Q
Modem
Modem
Section
Section
Dual Channel
TX Passive
Filter
Dual Channel
Dual Channel
TX Passive
TX Passive
Filter
Filter
Dual Channel
RX Passive Filter
Dual Channel
Dual Channel
RX Passive Filter
RX Passive Filter
Dual Channel
RX Active Filter
Dual Channel
Dual Channel
RX Active Filter
RX Active Filter
Power Supply
(with ST Viper 12A)
Power Supply
Power Supply
(with ST Viper 12A)
(with ST Viper 12A)
Connection to
Connection to µ
µC Board
C Board
Connection to
Connection to
Mains Supply
Mains Supply

AN2744 Board description
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Figure 7. Modem and coupling interface schematic

Board description AN2744
16/56
Figure 8. Power supply schematic
HIGH
VOLTAGE
SECTION

AN2744 Board description
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Table 3. Bill of materials
Item Q.ty Reference Value Description
116
ATOP1, ATOP2, P5 V, 10 V,
VADJ, TX, RXTX, RXFO, RX,
RAI, GND, CLRT, CL, CD/PD,
BU, ATO
Test point
2 1 CN1 CON50A 50-pin female connector
3 1 CN2 Header 2 Mains supply connector
4 1 C1 470 pF 630 V EVOX-RIFA PFR5-471J630L4
5 1 C2 47 nF X2 Epcos B32921-A2473K
61 C3 470 µF 16 V
electrolytic Rubycon YK / Yageo SE-K / Nichicon VK
7 1 C4 100 µF 16 V TDK CKG57DX7R-1C107M
82 C5,C10 10 µF 400 V
electrolytic Yageo SE-K / Nichicon VK
9 1 C6 2.2 nF Y2 TDK CD12E2GA222MYNS
10 1 C8 47 nF
11 3 C9,C17,C21 10 µF TDK C3216X7R-1C106M
12 2 C11,C12 270 pF
13 5 C13,C15,C18,C19,C24 100 nF
14 2 C14,C26 10 nF
15 1 C16 4.7 nF
16 1 C20 10 nF
17 1 C22 18 pF
18 1 C23 47 pF
19 1 C25 100 pF
20 1 C27 56 nF 50 V
21 1 C28 100 nF X2 10% Epcos B32922-A2104K
22 1 C29 150 nF
23 1 C30 220 pF
24 1 D1 DF06S 600 V - 1.5 A bridge rectifier
25 1 D2 Green LED
26 1 D3 STPS1H100
27 1 D4 STTH1L06A
28 1 D5 BAS16 2L BAS21 also suitable
29 1 D6 SM6T6V8CA 6.8 V bidirectional Transil™ diode
30 1 D7 ESDA6V1L 6.1 V ESD Transil™ diode
31 1 D9 BZX84C8V2 8.2 V Zener diode
32 1 F1 FUSE 2 A time-lag (T)

Board description AN2744
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Item Qty Reference Value Description
33 1 JP1 Jumper Leave open
34 2 JP2, JP3 Jumper Close 2-3
35 1 L1 33 µH Epcos B82462-A4333K
36 1 L2 2x10 mH - 0.3 A Radiohm 42V15-0307
37 1 L3 470 µH Epcos B82442-A1474K
38 1 L4 1 mH Epcos B82442-H1105K
39 1 L5 100 µH 10% Würth 744-775-210K / Epcos B82464-A4104K
40 1 L6 68 µH 10% Würth 744-775-168K / Epcos B82464-A4683K
41 1 L7 330 µH 10% Würth 744-774-233K
42 1 L8 10 µH Epcos B82432-T1103K
43 2 Q2, Q4 2N7002
44 1 Q3 BC857BL
45 1 R1 220 kΩ
46 1 R2 1K5
47 1 R3 10R 1 W Metal oxide - radial
48 1 R6 560
49 2 R8, R18 330
50 1 R9 1K2
51 1 R10 100 kΩ
52 1 R11 4K7
53 1 R12 680
54 3 R13, R14, R15 5K1
55 2 R16, R17 1M
56 1 R19 2 kΩ
57 1 R20 3K9
58 1 R21 3R3
59 1 R22 2K2
60 1 R23 10 kΩ
61 1 T1 SMPS transformer TDK SRW12.6ES-ExxH013 / Würth S06-100-057
62 1 T2 Line transformer VAC T60403-K5024-X044 / Radiohm 69H14-2101
63 1 U1 SFH610-A Optoswitch
64 1 U2 LCA710 Optoswitch - 3750 V isolation
65 1 U3 ST7538Q Power line transceiver
66 1 U6 VIPer12AS-E SMPS controller / switch
67 1 X1 16 Mhz Jauch Q 16.0-SS2-16-30/50-FU
Table 3. Bill of materials (continued)

AN2744 Board description
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Table 4. ST parts on the ST7538Q dual channel reference design board
Value Description
ST7538Q Power line transceiver
VIPer12AS-E SMPS controller / switch
STTH1L06A Ultrafast diode
STPS1H100 Schottky diode
SM6T6V8CA 6.8 V bidirectional Transil™ diode
ESDA6V1L 6.1 V ESD Transil™ diode

Board description AN2744
20/56
5.1 Line coupling interface
The line coupling interface is composed of three different filters: the dual channel Tx passive
filter, the dual channel Rx passive filter and the dual channel Rx active filter. The coupling
interface structure is represented in Figure 9.
All three filters are described in Section 5.1.2, Section 5.1.3 and Section 5.1.3.For each
filter, calculations and measured frequency responses are given.
The filters are quite sensitive to the components' value tolerance. Actual components used
in the ST7538Q dual channel reference design have the following tolerances:
●+/- 10% for coils and for the X2 capacitor
●+/- 1% for SMD resistors
●+/- 5% for SMD ceramic capacitors
To evaluate sensitivity to the tolerances indicated above, the following sections include
simulated responses of the filters with Montecarlo statistical analysis. Statistical simulation
helps to understand the relationship between tolerance of components' value and variations
Figure 9. Schematic of Rx and Tx filters
Tx PASSIVE FILTER
Rx
PASSIVE
FILTER
Rx ACTIVE FILTER
CMINUS
5V
C15
100nF COUT
R15
5K1
R14
5K1
ACT_IN
CPLUS
ATOP1
ATOP2
A
CT_IN
CH2
P
N
3
1
2
Q2
2N7002
CH2
R8
330
RAI
3 1
2
JP2
CLOSE 2-3
NEG_CH2
JP1
LEAVE OPENED
1
2
6 4
U2
LCA710
R17
1M
L5
100 uH
R10
100K
C11
270pF
R13
5K1
R9
1K2
R12
680
C12
270pF
3
1
2
Q4
2N7002
R16
1M
3
1
2
D7
ESDA6V1L
31
2
JP3
CLOSE 2-3
C16
4.7nF
C20
10nF
L7
330uH
R18
330
C29
150 nF
D6
SM6T6V8CA
1 8
4 5
T2
LINE TRANSFORMER C28
100nF X2
L6
68 uH
C27
56 nF
R21
3.3
C14
10 nF
Tx PASSIVE FILTER
Rx
PASSIVE
FILTER
Rx ACTIVE FILTER
CMINUS
5V
C15
100nF COUT
R15
5K1
R14
5K1
ACT_IN
CPLUS
ATOP1
ATOP2
A
CT_IN
CH2
P
N
3
1
2
Q2
2N7002
CMINUS
5V
C15
100nF COUT
R15
5K1
R14
5K1
ACT_IN
CPLUS
ATOP1
ATOP2
A
CT_IN
CH2
P
N
3
1
2
Q2
2N7002
CH2
R8
330
RAI
3 1
2
JP2
CLOSE 2-3
NEG_CH2
JP1
LEAVE OPENED
1
2
6 4
U2
LCA710
R17
1M
L5
100 uH
R10
100K
C11
270pF
R13
5K1
R9
1K2
R12
680
C12
270pF
3
1
2
CH2
R8
330
RAI
3 1
2
JP2
CLOSE 2-3
NEG_CH2
JP1
LEAVE OPENED
1
2
6 4
U2
LCA710
R17
1M
L5
100 uH
R10
100K
C11
270pF
R13
5K1
R9
1K2
R12
680
C12
270pF
3
1
2
Q4
2N7002
R16
1M
3
1
2
D7
ESDA6V1L
31
2
JP3
CLOSE 2-3
C16
4.7nF
C20
10nF
L7
330uH
R18
330
C29
150 nF
D6
SM6T6V8CA
1 8
4 5
T2
LINE TRANSFORMER C28
100nF X2
L6
68 uH
C27
56 nF
R21
3.3
C14
10 nF