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AN2451

Board description

Doc ID 12791 Rev 3

13/55

5 Board

description

The ST7540 reference design is composed of the following sections:

●

Power supply section, based on ST’s VIPer12A-E IC

●

ST7540 modem and crystal oscillator section

●

Line coupling interface section, with three subsections:

–

Transmission active filter

–

Transmission passive filter

–

Receiving passive filter.

The board also has two connectors, which allow the user to plug the mains supply on one
side of it and the I.B.U. communication board on the other side.

Figure 6.

Positioning of the various sections of the board

The schematics of the whole reference design appear in

Figure 7

and

Figure 7

shows

the modem and the coupling Interface circuits, while

Figure 8

represents the power supply

circuit. In both the 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 given in

and

Содержание ST7540

Страница 1: ...fically tailored to match powerline coupling requirements and to operate within a wide range of the input mains voltage Modem and crystal oscillator section Line coupling interface section The couplin...

Страница 2: ...pedance 24 5 2 Conducted disturbances 25 5 2 1 Conducted emissions 25 5 2 2 Noise immunity 26 5 3 Thermal design 29 5 4 Oscillator section 32 5 5 Surge and burst protection 32 5 6 50 pin connector for...

Страница 3: ...AN2451 Contents Doc ID 12791 Rev 3 3 55 Appendix A Board layout 51 List of normative references 54 Revision history 54...

Страница 4: ...missions test setup 26 Figure 19 Output spectrum typical at 72 kHz 2400 baud deviation 1 mains 220Vac 26 Figure 20 Narrow band conducted interference test setup 27 Figure 21 Measured BER vs SNR curve...

Страница 5: ...Vs AC_IN peak detector response 45 Figure 46 Example schematic for non isolated solution 46 Figure 47 Line coupling interface for 110 kHz channel 47 Figure 48 Line coupling interface for 132 5 kHz ch...

Страница 6: ...Bill of materials 16 Table 4 ST parts on the ST7540 reference design board 18 Table 5 Line coupling transformer specifications 21 Table 6 Noise immunity test settings 27 Table 7 50 pin connector digi...

Страница 7: ...onic distortion at mains output Loaded with CISPR 16 1 network 55 dBC 3rd harmonic distortion at mains output Loaded with CISPR 16 1 network 61 50Hz attenuation 100 dB Receiving specifications Rx mode...

Страница 8: ...0 kHz Table 1 Electrical characteristics of the ST7540 reference design continued Parameter Test conditions Value Unit Min Typ Max Table 2 Output voltage level setting through Vsense partitioning typi...

Страница 9: ...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 s...

Страница 10: ...he communication protocol stack A reset output RSTO and a programmable clock MCLK can be provided to the microcontroller by the ST7540 in order to simplify the external logic and circuitry The host co...

Страница 11: ...7540 power line modem demo kit software tool one EVALCOMMBOARD hosting the ST7 microcontroller one ST7540 reference design board EVALST7540 2 The correct procedure for connecting the EVALST7540 2 and...

Страница 12: ...xact transmitted bit sequence This can be done in two ways via the ST7540 control register settings the internal configuration register of the modem has a frame header field in which an 8 or 16 bit he...

Страница 13: ...r to plug the mains supply on one side of it and the I B U communication board on the other side Figure 6 Positioning of the various sections of the board The schematics of the whole reference design...

Страница 14: ...Board description AN2451 14 55 Doc ID 12791 Rev 3 Figure 7 Modem and coupling interface schematic HIGH VOLTAGE SECTION...

Страница 15: ...16V R2 220k R2 220k R5 1k5 R5 1k5 R1 10R 1W R1 10R 1W L3 470uH L3 470uH 2 1 D4 D4 R3 10 K R3 10 K 1 3 2 D5 10V D5 10V C3 10uF 400V C3 10uF 400V L4 33 uH L4 33 uH 1 2 4 3 U2 U2 2 4 1 3 6 5 7 8 U1 U1 4...

Страница 16: ...2 C11 C12 33pF TDK C1005C0G 1H330J 13 2 C14 C27 10nF Murata GRM188R7 1H103K 14 4 C16 C18 C19 C25 100nF TDK C1608X7R 1H104K 15 2 C21 C33 150pF Murata GRM1885C 1H151J 16 1 C22 10uF Murata GRM21BR6 1A106...

Страница 17: ...03 1 43 1 R4 560 0603 1 44 1 R5 1K5 0603 1 45 1 R6 1K1 0603 1 46 1 R7 47K 0603 1 47 1 R8 15K 0603 1 48 1 R9 4K7 0603 1 49 1 R10 12K 0603 1 50 1 R12 1K 0603 1 51 1 R14 1K8 0603 1 52 1 R17 470 0603 1 53...

Страница 18: ...2 capacitor 1 for SMD resistors 5 for SMD ceramic capacitors To evaluate sensitivity of the filters to the tolerances listed above the following sections include simulated responses of the filters wit...

Страница 19: ...s stage and a Sallen Key 2 pole cell with 9dB gain The R19 C32 low pass stage is aimed at introducing attenuation starting from approximately an octave above the transmission channel frequency The tra...

Страница 20: ...rance effect 5 1 2 Tx passive filter Coupling to the power line requires some passive components in addition to the active filtering stage In particular Tx passive filter section is made of the decoup...

Страница 21: ...er without inserting series inductance L5 L6 The drawback however is the poor accuracy of this parameter which can lead to a shift of the filter response and to bad coupling Consequently a low leakage...

Страница 22: ...d to the CISPR network with the components tolerance effect 5 1 3 Rx passive filter The Rx filter is made up of a resistor in series with a parallel L C resonant The transfer function of the filter ca...

Страница 23: ...transfer if RL is set to zero Looking at the first way to express the module of the transfer function it is possible to notice that a higher value of Q can help keeping the losses small Nevertheless a...

Страница 24: ...s in both Tx and Rx mode In both figures channel impedance point and the minimum impedance point are indicated The impedance magnitude values prove that the ST7540 reference design board is compliant...

Страница 25: ...bances 5 2 1 Conducted emissions The EN50065 1 standard describes the test setup and procedures for testing conducted emissions The conducted emissions measurements have been taken with 220 Vac mains...

Страница 26: ...k traced in red may be compared to the typical output spectrum of the ST7540 reference design board Figure 19 Output spectrum typical at 72 kHz 2400 baud deviation 1 mains 220Vac 5 2 2 Noise immunity...

Страница 27: ...trum Analyzer allows measurement of the actual signal and noise levels as seen by the receiving ST7540 internal circuitry programmed for 2400 baud Figure 21 represents the BER vs SNR curve in the pres...

Страница 28: ...ulated signal has been decreased until the measured BER was lower than 10 3 one error every 1000 transmitted bits Figure 22 shows SNR vs frequency curves for both a pure sinusoidal and an AM modulated...

Страница 29: ...issipating area on the bottom side is nearly 1 5 cm2 Figure 23 PCB copper dissipating area for ST7540 reference design board Even if the ST7540 features a built in thermal shutdown circuitry which tur...

Страница 30: ...wer that is well above the one sustainable at steady state For this reason a complete thermal analysis requires taking into account the characteristics of the transmission i e duty cycle and duration...

Страница 31: ...40 reference design Figure 27 Dissipated power vs load impedance modulus typical curve for ST7540 reference design board Referring to the relationship between dissipated power and temperature it can b...

Страница 32: ...apacitors No tracks or vias should cross the ground plane except for the crystal connections It is also recommended to use a large clearance on the oscillator related tracks to minimize humidity probl...

Страница 33: ...e 1 2 x 50 s Fast transient burst tests are specified at level 2 kV with pulse shape 5 x 50 ns and pulse frequency 5 kHz Figure 29 Figure 30 and Figure 31 illustrate the protection criteria implemente...

Страница 34: ...Board description AN2451 34 55 Doc ID 12791 Rev 3 Figure 30 Common mode disturbances protection negative disturbance Figure 31 Differential mode disturbances protection...

Страница 35: ...ode An Analog Input ANALOG_IN which is a line intended to implement a Received Signal Strength Indicator a peak meter used to give an Rx signal level estimation A VDDF_FORCE signal which forces the mi...

Страница 36: ...cup mode The power supply is designed in isolated flyback configuration Secondary regulation implemented through an optocoupler and a Zener diode takes the requested output tolerance for the specified...

Страница 37: ...ke the maximum reverse voltage and the RMS secondary current into account A STPS1H100 Power Schottky rectifier has been chosen for this purpose A LC filter has been added on the output consisting of L...

Страница 38: ...on stops the device operation until the device temperature falls The startup phase could be critical for the SMPS Output overshoot occurs if the circuit is not properly designed Care must be taken in...

Страница 39: ...6 Typical waveforms at 265 Vac startup Ch1 freq 23 50 Hz green Ch4 max 2 08 A light blue Ch4 mean 383 mA light blue Ch1 max 702 V black Ch2 mean 19 72 V green Ch4 max 500 mA light blue VDS IOUT VDD 11...

Страница 40: ...and the VIPer are forced to operate close to their current limitations and thus the efficiency is reduced In general efficiency is affected by the losses which are due to R1 series input resistor lim...

Страница 41: ...master node The main characteristics of this tool are indicated in red Figure 39 ST7540 powerline modem demonstration kit window for the master board Special controls are included in the ping test Re...

Страница 42: ...ach meter is placed on This information is mainly useful at system level in order to check for unexpected losses on the distribution line due to failures or energy theft Since the three phases on the...

Страница 43: ...h a current flowing into the LED of the optocoupler can minimize the delay between the actual zero crossing of the mains voltage and the edge of the ZC_OUT signal if the optocoupler has been chosen to...

Страница 44: ...of the incoming signal is useful to Evaluate the SNR signal to noise ratio at the node Choose the best routing through the network if repeaters are allowed One possible implementation for the receive...

Страница 45: ...ure sinusoidal waveform at the input The DC_OUT signal should be converted through an integrated A D converter by the application microcontroller Figure 45 Measured DC_OUT Vs AC_IN peak detector respo...

Страница 46: ...the ac dc SMPS For example the L5970 DC DC step down switching regulator can be used in case of 24 V bus to obtain the 12 V supply for the ST7540 device 7 6 110 and 132 5 kHz coupling circuit In this...

Страница 47: ...AN2451 Application ideas Doc ID 12791 Rev 3 47 55 Figure 47 Line coupling interface for 110 kHz channel...

Страница 48: ...Application ideas AN2451 48 55 Doc ID 12791 Rev 3 Figure 48 Line coupling interface for 132 5 kHz channel...

Страница 49: ...transmit What to check a Check the voltage on the PA_OUT test pad with the oscilloscope ground probe connected to the SVss signal ground The programmed carrier frequency must be present on the PA_OUT...

Страница 50: ...k if data are present on the RxD pin 6 Problem during a ping test or a transmission test the ST7540 reference design board shows high bit error rate Note This point refers to a half duplex communicati...

Страница 51: ...AN2451 Board layout Doc ID 12791 Rev 3 51 55 Appendix A Board layout Figure 49 PCB layout component placing...

Страница 52: ...Board layout AN2451 52 55 Doc ID 12791 Rev 3 Figure 50 PCB layout top view...

Страница 53: ...AN2451 Board layout Doc ID 12791 Rev 3 53 55 Figure 51 PCB layout bottom view...

Страница 54: ...ty requirements Part 4 2 Low voltage decoupling filters safety requirements Part 7 Equipment impedance Revision history Table 12 Document revision history Date Revision Changes 10 Jan 2007 1 First iss...

Страница 55: ...ARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION OR INFRINGEMENT OF ANY PATENT COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT UNLE...

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