AD9876-EB Analog Devices Inc, AD9876-EB Datasheet - Page 24

• Manufacturer Part Number: AD9876-EB
• Description: BOARD EVAL FOR AD9876
• Manufacturer: Analog Devices Inc

Specifications of AD9876-EB

• Rohs Status: RoHS non-compliant
• Module/board Type: Evaluation Board
• For Use With/related Products: AD9876

AD9876
on the MxFE side of the ferrite as well as a low ESR, ESL
decoupling capacitors on each supply pin (i.e., the AD9876
requires five power supply decoupling caps, one each on Pins 5,
38, 47, 14, and 35). The decoupling caps should be placed as close
to the MxFE supply pins as possible. An example of the proper
decoupling is shown in the AD9876 evaluation board schematic.
Ground Planes
In general, if the component placing guidelines discussed earlier
can be implemented, it is best to have at least one continuous
ground plane for the entire board. All ground connections should be
made as short as possible. This will result in the lowest impedance
return paths and the quietest ground connections.
If the components cannot be placed in a manner that will keep the
high frequency ground currents from traversing under the MxFE
and analog components, it may be necessary to put current steering
channels into the ground plane to route the high frequency
currents around these sensitive areas. These current steering
channels should be made only when and where necessary.
Revision History
Location
10/02—Data Sheet changed from REV. 0 to REV. A.
Changes to to Table IV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Changes to REGISTER 3—CLOCK SOURCE CONFIGURATION section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1.45
1.40
1.35
0.15
0.05
ROTATED 90 CCW
SEATING
PLANE
VIEW A
0.08 MAX
COPLANARITY
48-Lead Plastic Quad Flatpack [LQFP]
0.20
0.09
3.5
7
0
COMPLIANT TO JEDEC STANDARDS MS-026BBC
Dimensions shown in millimeters
OUTLINE DIMENSIONS
SEATING
PLANE
1.60 MAX
0.75
0.60
0.45
1.4 mm Thick
(ST-48)
–24–
INDICATOR
Signal Routing
The digital Rx and Tx signal paths should be kept as short as
possible. Also, the impedance of these traces should have
a controlled characteristic impedance of about 50 Ω. This will
prevent poor signal integrity and the high currents that can
occur during undershoot or overshoot caused by ringing. If the
signal traces cannot be kept shorter than about 1.5 inches, series
termination resistors (33 Ω to 47 Ω) should be placed close to
all signal sources. It is a good idea to series-terminate all clock
signals at their source, regardless of trace length.
The receive Rx
signals on the entire board. Careful routing of these signals
is essential for good receive path performance. The Rx
Rx
together as a pair. By keeping the traces adjacent to each other,
noise coupled onto the signals will appear as common mode and
will be largely rejected by the MxFE receive input. Keeping the
driving point impedance of the receive signal low and placing
any low-pass filtering of the signals close to the MxFE will
further reduce the possibility of noise corrupting these signals.
PIN 1
VIEW A
signals form a differential pair and should be routed
BSC
0.50
12
1
48
13
(PINS DOWN)
TOP VIEW
9.00 BSC
and Rx
24
37
0.27
0.22
0.17
36
25
signals are the most sensitive
7.00
BSC
REV. A
and
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