AD8115AST datasheet(24/26 Pages) AD

24 / 26 page

AD8114/AD8115

–24–

REV. 0

RESET

CLK

DATA IN

DGND

UPDATE

MOLEX 0.100" CENTER

CRIMP TERMINAL HOUSING

D-SUB 25 PIN (MALE)

EVALUATION BOARD

SIGNAL

RESET

UPDATE

DATA IN

CLK

DGND

MOLEX

TERMINAL HOUSING

D-SUB-25

Figure 52. Evaluation Board-PC Connection Cable

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 51 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.

w = 0.008"

(0.2mm)

a = 0.008"

(0.2mm)

b = 0.0514"

(1.3mm)

h = 0.025"

(0.63mm)

t = 0.00135" (0.0343mm)

TOP LAYER

SIGNAL LAYER

POWER LAYER

BOTTOM LAYER

Figure 51. Cross Section of Input and Output Traces

The board has 32 BNC type connectors: 16 inputs and 16

outputs. The connectors are arranged in a crescent around the

device. As can be seen from Figure 47, this results in all 16

input signal traces and all 16 signal output traces having the

same length. This is useful in tests such as All-Hostile

Crosstalk where the phase relationship and delay between

signals 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

evaluation board’s analog and digital power supply pins.

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. Fi-

nally a 10

µF capacitor should be used to decouple power sup-

plies as they come onto the board.

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