Echelon LonWorks USB Network Interface - Manual (Page 20)

14 L ON W ORKS USB Network Interface User’s Guide
Alternate Power Line Coupling Circuit
This appendix describes how to design a power supply and coupling circuit for the
U20 interface. Before attempting to do so, you must carefully read and
understand Chapter 4, Coupling Circuits, of the PL 3120 / PL 3150 Power Line
Smart Transceiver Data Book.
You also need to understand the power requirements of the U20 interface, and
the circuitry provided in the U20 interface and wall-plug coupling circuit/power
supply. These topics are described in this appendix.
U20 USB Network Interface Power Requirements
The U20 interface draws power through both the USB Series “A” plug and the
barrel connector (marked PL-20). The interface draws 5V power (used to power
most of the internal interface circuits) from the Series “A” connector. The
transmit amplifier power supply draws power through the barrel connector, and
the barrel connector is also used for coupling power line communication signals
back onto the power line network.
The U20 interface will draw no more than 50mA through the 5V USB Series “A”
plug. Table A.1 summarizes the U20 interface’s power requirements drawn
through the barrel connector:
Table A.1 Power Requirements Through Barrel Connector
Parameter Min Typ Max Units Description
Voltage 10 14 18 Volts DC voltage required for the U20
interface transmit amplifier.
Current --- --- 250 Milliamps Peak transmit current require
during packet transmissions.
The barrel connector on the U20 interface is a 2.1mm DC power jack with the
following pin out:
POSITIVE TIP
(+) NEGATIVE BARREL
(-)
Figure A.1 U20 USB Network Interface Barrel Connector Pin Out
Wall-Plug Power Supply and Coupling Circuit
As you begin designing your own power line coupling circuit, it is imperative that
you carefully study the coupling circuits inside the U20 interface, as well as the
circuitry inside the supplied wall-plug coupling circuit/power supply. You must
also carefully read and understand the Wall-Plug Coupler and Power Supply
section in Chapter 4 of the PL 3120/PL 3150 Power Line Smart Transceiver Data
Book.