Echelon LonWorks USB Network Interface - Manual (Page 22)

16 L ON W ORKS USB Network Interface User’s Guide
Ferrite
Bead
TX
AMP
RX
Front
End
VA
RXIN
RXCOMP
2.1mm
DC Power Jack
Figure A.3 Coupling Circuit and Power Supply Input Schematic
This is the same circuit that is described for the Line-to-Neutral (L-to-N) Isolated
Wall-Plug Power Supply/Coupler in the PL 3120 / PL 3150 Power Line Smart
Transceiver Data Book. For more information on this combined power supply
and coupling circuit, see the Wall-Plug Coupler and Power Supply section in
Chapter 4 of the PL 3120 / PL 3150 Power Line Smart Transceiver Data Book.
10.8-18VDC Automotive Coupling
If your DC power line network is in the range of 10.8 to 18VDC (i.e. truck or
automobile 12VDC supplies), then you can connect the U20 interface’s barrel
connector directly to the DC supply. Be sure to observe the proper polarity on the
barrel connector.
Keep in mind that large capacitors (>4700pF) present a low impedance to power
line communications signals and can cause significant attenuation. The
allowable amount of impedance across the line is application dependant
(distance, network impedance, etc.). If your application is suffering from
communications problems due to attenuation, you should consider adding series