Appendix B: PCB Layout Suggestion
The following shows an example
of a PCB layout using option
#021 that would result in good
electrical and EMI performance.
Things to note:
1. The ground plane should be
continuous under the part, but
should not extend under the
shield trace.
2. The shield trace is a wide, low
inductance trace back to the
system ground.
3. The AGND pin is connected to
the ground plane and not to
the shield tab.
4. C1 and C3 are optional supply
filter capacitors; they may be
left out if a clean power sup-
ply is used.
5. VLED can be connected to
either unfiltered or unregu-
lated power supply. If VLED
and V
CC
share the same power
supply and C1 is used, the
connection should be before
the C1 cap. In a noisy envi-
ronment, supply rejection can
be enhanced by including C3
as well.
COMPONENT SIDE
C2
R1
C1
C3
SHUTDOWN
SYSTEM
GROUND
SHIELD
VLED
TXD
V
CC
RXD
CIRCUIT SIDE
Figure 18. PCB layout suggestions.
13
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
