
The objective of the T2 CDN in the figure is to drive the large common-mode noise
signal into the EUT’s network cable, while still isolating the AE unit’s network cable
from the noise. See the EN 61000-4-6 test standard
and related articles for more
information about test setups and procedures.
The following figure shows the changes in the EN 61000-4-6 test setup to
accommodate shielded twisted pair (STP) networks. An S2 CDN is used instead of
the T2 CDN, and the shield should be connected to earth ground.
Figure 6.5
Typical EN 61000-4-6 Test Set-up for Shielded Twisted Pair (STP)
Figure 6.6 shows the EN 61000-4-6 common-mode (CM) noise immunity of the
LPT-11 transceiver in a typical device during a 15Vrms scan
using unshielded twisted
pair. The LPT-11
transceiver-based device passes the 10Vrms EN-61000-4-6 Level 3
scan with good
margin. For comparison, the CM noise immunity of the LPT-10 transceiver
is also
plotted in the figure. The CM noise immunity of the LPT-11 transceiver is
significantly better than the LPT-10 transceiver.
L
ON
W
ORKS
LPT-11 Transceiver User’s Guide
6-11