User`s guide

LONWORKS LPT-10 Transceiver User’s Guide 5-7
Power Specifications, Simplified Form
A link power network allows for multiple branches, e.g., a star topology. A branch is
defined as any length of twisted pair cable that extends from the LPI-10 module. Loop
topologies can be formed by joining the ends of branches.
Whereas system and transmission distance specifications involve the entire network,
power specifications apply to individual branches. The closer the nodes on a branch are
to the LPI-10 module, the more nodes that can be on that branch. Similarly, the fewer
the nodes on a branch, the longer that branch can be.
Both nominal and worst case power specifications for the performance of the link power
system, with both lumped and distributed loads, are shown in tables 5.3 through 5.5.
Nominal conditions include: nominal node temperature (+25°C), nominal average wire
temperature (+25°C), nominal manufacturing variations, nominal line-voltage
variations, and nominal LPI-10 module output voltage. The worst case values are
derated for all of these variations.
The following section, “Power Specifications for Extended Performance,” may be used as
an alternative to tables 5.1 through 5.3. It is more complex, but will allow better
performance for certain topologies.
Multiple link power systems may be interconnected via physical layer repeaters or
routers to extend distance, number of nodes, and total available application current.
Table 5.3 Simplified Power Specifications Using Belden 85102 or Belden
8471 (16AWG/1.3mm) Wire
Nominal Worst
Case
Units
500 meter branch length,
Evenly distributed loading along a bus
application current: 25 mA 128 128 nodes
50 mA 64 64
100 mA 32 32
500 meter branch length,
Lumped loading or otherwise distributed
application current: 25 mA 112 81 nodes
50 mA 56 40
100 mA 28 20
400 meter branch length,
Lumped loading or otherwise distributed
application current: 25 mA 128 101 nodes
50 mA 64 50
100 mA 32 25