AD4080BBCZ datasheet(71/94 Pages) AD

71 / 94 page

Data Sheet

AD4080

LAYOUT GUIDELINES

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Rev. A | 71 of 94

The AD4080 includes all critical bypass capacitors within the device

package, which greatly reduces the layout challenge for a precision,

high-speed converter. These integrated capacitors are optimally

placed within the device package to ensure that maximum perform-

ance is easily obtained. However, as with any precision mixed

signal device, care must be taken in system device placement

to ensure that there is proper partitioning of the critical analog

signal chain component routing and routing of the high-speed digital

signals to prevent unwanted coupling effects.

Note the following layout considerations:

►

The AD4080 contains internal decoupling on all power supplies,

AVDD33 (0.47 μF), VDD11 (1.88 μF), IOVDD (0.22 μF), as well

as VDDLDO (0.22 μF). Therefore, no external bypass capacitors

are required, saving board space and reducing bill of material

(BOM) count and sensitivity.

►

Ensure good partitioning of analog and digital domain signals

within the design by, for example, having all analog signals in

from the left-hand side and keeping dynamic digital signals on

the right-hand side.

►

Have a solid ground plane under the AD4080 and connect all

analog ground (GND) pins, reference ground (REFGND), and

digital ground (IOGND) pins to this shared plane.

►

Recommended connections of ground (GND), reference ground

(REFGND), and digital ground (IOGND) connections are shown

in Figure 107. It is recommended to not keep the current return

path of the reference IC in the same current loop as the current

return loop from the other circuitry on the PCB. Connect the

reference local star point to the ADC star point ground on the top

layer of the PCB as shown in Figure 107.

►

See Figure 108 for the side view cross-section of the PCB board

showing the ground planes distribution . Note that Figure 108

only shows the ground planes but does not including the signal

tracks.

Figure 107. AD4080 External Reference Ground Connections

Figure 108. Recommended PCB Ground Planes Layout

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