ADA4411-3

Rev. 0 | Page 13 of 16

PRINTED CIRCUIT BOARD LAYOUT

As with all high speed applications, attention to printed

circuit board layout is of paramount importance. Standard high

speed layout practices should be adhered to when designing

with the ADA4411-3. A solid ground plane is recommended,

and surface-mount, ceramic power supply decoupling

capacitors should be placed as close as possible to the supply

pins. All of the ADA4411-3 GND pins should be connected to

the ground plane with traces that are as short as possible.

Controlled impedance traces of the shortest length possible

should be used to connect to the signal I/O pins and should not

pass over any voids in the ground plane. A 75 Ω impedance

level is typically used in video applications. All signal outputs of

the ADA4411-3 should include series termination resistors

when driving transmission lines.

When the ADA4411-3 receives its inputs from a device

with current outputs, the required load resistor value for

the output current is often different from the characteristic

impedance of the signal traces. In this case, if the intercon-

nections are sufficiently short (<< 0.1 wavelength), the trace

does not have to be terminated in its characteristic impedance.

Traces of 75 Ω can be used in this instance, provided their

lengths are an inch or two at the most. This is easily achieved

because the ADA4411-3 and the device feeding it are usually

adjacent to each other, and connections can be made that are

less than one inch in length.

VIDEO ENCODER RECONSTRUCTION FILTER

The ADA4411-3 is easily applied as a reconstruction filter at

the DAC outputs of a video encoder. Figure 24 illustrates how to

use the ADA4411-3 in this type of application with an ADV7322

video encoder in a single-supply application with ac-coupled

outputs.