Microchip Technology PL485-EK, User Manual

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Figure 3-7. PLC Coupling Schematic on the PL485-EK Board
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PL485 - Evaluation Kit
05/12/2019 15:01:59
PLC Coupling.SchDoc
Project Title
Sch #: Date:
File:
Revision: Sheet
Designed with
Drawn By:
JLCF
Sheet Title
PLC Coupling
Engineer:
JLCF
03-PL485
B
Size
A3
PL485-EK
PartNumber:
Variant Name
CEN-B
Altium.com
1k
R35
1 2
3
PMBD7000
D16 AGND
4.02k
1%
R36
10000pF
C70
PL_AGC
16R
R37
100pF
C71
AGND
PLC_RX
TP17
TP12
TP13
TP16
YELLOW
D15
1k
R33
1
2 3
BC807
Q2
GND
3V3
GND
33k
R31
TP14
300R
R32 470uH
L9
0R
R34
3
1
2
DMN2056U
Q3
3
1
2
DMN2056U
Q1
510R
0603
R27
0R
R28
1
2
3
BAT54SLT1
D13
10k
R26
10k
R21
GND
3V3
22uH
L6
2.2uH
L8
15uH
L7
1uF
25V
0805
C68
0.15uF
50V
1206
C67
3.3R
0805
1%
R24
0R
R23
PL_TXRX0
PL_TXRX1
PL_AGC
PL_VIN
PL_VZC
PL_EMIT
PLC Coupling
PL_TXRX0
PL_TXRX1
PL_AGC
PL_VIN
PL_VZC
PLC_Coupling
PL_EMIT
PL_TXRX0
PL_VIN
PLC Coupling
510k 1%
R25
510k 1%
R29
PLC+
PLC-
TP15
0R
R22
0R
R30
PL+
PL-
GND
SMAJ5.0CA-13-F
D14
10uF
C66
10uF
C69
TP21
PL_EMIT
3
2
1
Note: PLC coupling circuitry adds the yellow LED, D15, for visual indication of PLC frames transmission.
The following sections describe the aim of each sub-circuit assembled in the PL485-EK board.
3.3.2.1 PLC Filtering Circuit
The in-band flat response filtering stage reduces spurious emission to the limits set by the corresponding regulation
and blocks potential interferences from other transmission channels without distorting the injected signal.
The filtering stage used in PL485-EK, see Figure 3-7 , has three aims:
• Band-pass filtering of high frequency components of the square waveform generated by the transmission stage
• Adapt Input/Output impedance for optimal reception/transmission. This is controlled by TXRX0 signal
• A band-pass filtering for received signals
3.3.2.2 PLC Coupling Circuit
The PLC coupling circuit connects the PLC signal directly to DC power rails without requiring any hardware
adaptation (or to the mains grid using an AC coupler).
The main purpose of the circuit is to block the voltage of the rail to/from which the signal is injected/received. In
PL485-EK, it is carried out by the capacitors, C66 and C69, (see
Figure 3-7 ). Resistors R25 and R29 allow to
discharge C66 and C69 capacitors in case of disconnection from DC power rails.
D14 TVS diode protects the coupling circuit from the overvoltage and high transient voltages (surges and spikes)
from DC power rails.
CAUTION
PLC coupling components are designed for a maximum voltage of 48 V
DC
.
Important: In case of using the AC coupler accessory, it is recommended to remove R22 and R30 for
better performance. Please refer to PLC-AC-Coupler User Guide for more information about the AC
coupler accessory.
3.3.2.3 PLC Reception Circuit
The PLC reception circuit used in PL485-EK, see Figure 3-7 , is the reference design for the reception stage and it is
composed of:
PL485-EK
PL485-EK Board
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2020 Microchip Technology Inc.
User Guide
DS50002954B-page 16