AD8109-EB Analog Devices, AD8109-EB Datasheet - Page 25

• Manufacturer Part Number: AD8109-EB
• Description: 250MHz, 8x8 Buffered Video Crosspoint Switch(Gain=2)
• Manufacturer: Analog Devices

Optimized for video applications, all signal inputs and outputs
are terminated with 75 Ω resistors. Stripline techniques are used
to achieve a characteristic impedance on the signal input and
output lines also of 75 Ω. Figure 16 shows a cross-section of one
of the input or output tracks along with the arrangement of the
PCB layers. It should be noted that unused regions of the four
layers are filled up with ground planes. As a result, the input
and output traces, in addition to having controlled impedances,
are well shielded.
The board has 16 BNC type connectors: eight inputs and eight
outputs. The connectors are arranged in two crescents around
the device. As can be seen from Figure 11, this results in all
eight input signal traces and all eight signal output traces having
the same length. This is useful in tests such as All-Hostile
Crosstalk where the phase relationship and delay between sig-
nals needs to be maintained from input to output.
The three power supply pins AVCC, DVCC, and AVEE should
be connected to good quality, low noise, ± 5 V supplies. Where
the same ± 5 V power supplies are used for analog and digital,
separate cables should be run for the power supply to the evalu-
ation board’s analog and digital power supply pins.
b = 0.024"
(0.6mm)
a = 0.008"
(0.2mm)
w = 0.008"
(0.2mm)
h = 0.011325"
(0.288mm)
t = 0.00135" (0.0343mm)
TOP LAYER
SIGNAL LAYER
POWER LAYER
BOTTOM LAYER
As a general rule, each power supply pin (or group of adjacent
power supply pins) should be locally decoupled with a 0.01 µF
capacitor. If there is a space constraint, it is more important to
decouple analog power supply pins before digital power supply
pins. A 0.1 µF capacitor, located reasonably close to the pins,
can be used to decouple a number of power supply pins. Finally
a 10 µF capacitor should be used to decouple power supplies as
they come on to the board.
Controlling the Evaluation Board from a PC
The evaluation board include Windows-based control software
and a custom cable that connects the board’s digital interface to
the printer port of the PC. The wiring of this cable is shown in
Figure 17. The software requires Windows 3.1 or later to oper-
ate. To install the software, insert the disk labeled “Disk #1 of
2” in the PC and run the file called SETUP.EXE. Additional
installation instructions will be given on-screen. Before begin-
ning installation, it is important to terminate any other Windows
applications that are running.
UPDATE
DATA IN
RESET
EVALUATION BOARD
DGND
CLK
CE
D-SUB-25
2
3
4
5
6
25
CRIMP TERMINAL HOUSING
MOLEX 0.100" CENTER
TERMINAL HOUSING
1
6
MOLEX
3
1
4
5
2
6
DGND
SIGNAL
CE
RESET
UPDATE
DATA IN
CLK
AD8108/AD8109
D-SUB 25 PIN (MALE)
14 1
25
PC
13