User`s guide

5-4
System Performance and Cable Selection
Link power performance has system, transmission, and power specifications which are
outlined on the following pages. Each of the specifications should be met to ensure
proper operation.
The system designer may choose a variety of cables, depending on cost, availability
and performance. Performance as outlined in the transmission and power specifications
varies with cable type. The wire resistance per unit length is a significant factor in the
power specification, since the system is designed to accommodate a substantial drop in
voltage along the wire according to Ohm's Law. The transmission specification
depends on such factors as resistance, mutual capacitance and the velocity of signal
propagation.
Echelon has characterized system performance on several cable types whose typical
electrical parameters are shown in table 5.1.
Table 5.1 Cable Parameters
Cable Type Wire dia.
/AWG
R
loop
Ω/km
C
nF/km
Vprop
% of c
Belden 85102, single twisted pair,
stranded 9/29, unshielded, plenum
1.3mm/16 28 56 62
Belden 8471, single twisted pair,
stranded 9/29, unshielded, nonplenum
1.3mm/16 28 72 55
Level 4/22AWG, twisted pair,
typically solid & unshielded
0.65mm/22 106 49 67
JY (St) Y 2x2x0.8, 4-wire helical twist,
solid, shielded
0.8 mm/20.4 73 98 41
If the cable has a shield, it should be connected to the LPI-10 module ground (at the P1
connector) via a 470kΩ, 1/4 Watt, ≤ 10%, metal film resistor to prevent static charge
build-up.
For more information on Level 4 cable, refer to [12].
Note that the specifications in Transmission Specifications are for one network
segment. Multiple segments may be combined using repeaters as described in chapters 1
and 2 to increase the number of nodes, application current, and distance. For example, a
free topology network containing 512 nodes and total wire length of up to 2000 meters
may be built using four segments interconnected by 3 repeaters, assuming network traffic
requirements are met.