hsdl3208 Avago Technologies, hsdl3208 Datasheet - Page 12

• Manufacturer Part Number: hsdl3208
• Description: Ultra Small Profile Package Irda Data Compliant Low Power 115.2 Kbit/s Infrared Transceiver - Agilent Hewlett-packard
• Manufacturer: Avago Technologies

Appendix B: PCB Layout Suggestion
The HSDL-3208 is a shieldless part
and hence does not contain a shield
trace, unlike the other transceivers.
The following PCB layout guide-
lines should be followed to obtain a
good PSRR and EM immunity,
resulting in good electrical
performance. Things to note:
1. The AGND pin should be
2. C1 and C2 are optional supply
3. VLED can be connected to either
4. Preferably a multi-layered board
12
connected to the ground plane.
filter capacitors; they may be left
out if a clean power supply is
used.
unfiltered or unregulated power
supply. If VLED and V
the same power supply and C1 is
used, the connection should be
before the current limiting
resistor R2. In a noisy environ-
ment, including capacitor C2 can
enhance supply rejection. C1 is
generally a ceramic capacitor of
low inductance providing a wide
frequency response while C2 is a
tantalum capacitor of big volume
and fast frequency response. The
use of a tantalum capacitor is
more critical on the V
which carries a high current.
should be used to provide
sufficient ground plane. Use the
layer underneath and near the
transceiver module as V
sandwich that layer between
ground connected board layers.
LED
CC
CC
share
line,
, and
The area underneath the module at
the second layer, and 3 cm in all
directions around the module, is
defined as the critical ground plane
zone. The ground plane should be
maximized in this zone. Refer to
application note AN1114 or the
Agilent IrDA Data Link Design
Guide for details. The layout below
is based on a 2-layer PCB.
Figure 18. PCB layout suggestion.
Refer to the diagram below for
an example of a 4-layer board.
Top View
Bottom View
TOP LAYER
CONNECT THE METAL SHIELD AND MODULE
GROUND PIN TO BOTTOM GROUND LAYER.
LAYER 2
CRITICAL GROUND PLANE ZONE. DO NOT
CONNECT DIRECTLY TO THE MODULE
GROUND PIN.
LAYER 3
KEEP DATA BUS AWAY FROM CRITICAL
GROUND PLANE ZONE.
BOTTOM LAYER (GND)