Echelon LonWorks Router - Manual (Page 78)

Designator Value
U1 TDA3663 (or similar LDO regulator)
U2 74AHCT1G126
U3 74AHCT1G04 (or a 74AHCT1G126
with OE tied high)
Important: Because the Router 5000 XOUT pin drives the FTT-10A CLK
signal, the value of C2 does not match the value of C1. The value for C2 is
specified as 30 pF based on an input capacitance for the buffer/line driver of 3 pF
at 25 ºC (so that the total capacitance for the XOUT pin is 33 pF). For the
74AHCT1G126 part, input capacitance can vary over temperature, up to 10 pF.
If your device is likely to experience extreme temperatures, consider changing the
value of C2 to 27 pF to allow for the change in capacitance over temperature.
See the L
ON W ORKS FTT-10A Free Topology Transceiver User’s Guide for
additional information about selecting appropriate parts for capacitors C8 and
C9, for using fast switching rectifiers in place of diodes D3 and D4, and for
replacing the PCB spark gaps with fast surge protectors with microgaps in
applications that must be conformally coated or potted.
See the L
ON W ORKS FTT-10A Free Topology Transceiver User’s Guide for PCB
layout guidelines for the FTT-10A transceiver; see PCB Layout Guidelines and
the Series 5000 Chip Data Book for PCB layout guidelines for the Router 5000.
Using an LPT-11 Link Power Transceiver
The Echelon L ON W ORKS LPT-11 Link Power Twisted Pair Transceiver provides a
simple, cost effective method for adding a network-powered L ON W ORKS
transceiver to any Neuron Chip-based sensor, activator, display, lighting device,
or general purpose I/O controller. The LPT-11 transceiver consists of a Single In-
Line Package (SIP) that contains a 78 kbps differential Manchester coded
communications transceiver, a switching power supply that draws power from
the twisted-pair network, and connections for the Router 5000 Communications
Port (CP) lines and for the twisted pair network. The LPT-11 transceiver
eliminates the need to use a local power supply for each device, because device
power is supplied by a central power supply over the same twisted wire pair that
handles network communications. A single network segment can support up to
128 LPT-11 based devices.
The LPT-11 transceiver includes an integral switching power supply that can
furnish +5 VDC at up to 100 mA. The LPT-11 transceiver derives its power
directly from the switching power supply, leaving up to 100 mA of current for a
Router 5000, application electronics, sensors, actuators, and displays. If a high-
current or high-voltage device must be controlled, then the +5 VDC power can be
used to trigger an isolating high-current triac, relay, or contactor.
The link-power system uses a single point of Earth ground, at the LPI-10 module,
and all of the LPT-11 transceivers electrically float relative to the local ground.
Differential transmission minimizes the effects of common-mode noise on signal
transmission. If grounded sensors or actuators are used, then either the
68 Developing a LONWORKS Router