Data Sheet

ADA4930-1/ADA4930-2

Rev. D | Page 23 of 25

LAYOUT, GROUNDING, AND BYPASSING

The ADA4930-1/ADA4930-2 are high speeddevices. Realizing

their superior performancerequiresattention to the details of

high speed PCB design.

The first requirement is tousea multilayer PCB with solidground

and powerplanesthat coveras muchoftheboardarea aspossible.

Bypasseach power supply pindirectlyto anearby groundplane, as

close to thedeviceaspossible. Use0.1 µF highfrequency ceramic

chip capacitors.

Provide low frequency bulkbypassing, using 10 µF tantalum

capacitors from each supply to ground.

Stray transmission linecapacitancein combination withpackage

parasitics can potentially form a resonantcircuit at high

frequencies, resulting in excessive gain peaking or possible

oscillation.

Signal routing should be short and direct to avoid such parasitic

effects. Provide symmetrical layout forcomplementary signals

to maximize balanced performance.

Figure 56. ADA4930-1 Ground and Power Plane Voiding

in the Vicinity of RF and RG

Use radio frequency transmission lines to connect the driver

and receiver to the amplifier.

Minimize stray capacitance at the input/output pins by clearing

the underlying ground and low impedanceplanes near thesepins

(see Figure 56).

If the driver/receiveris more than one-eighth of thewavelength

from the amplifier, the signal trace widths should be minimal.

This nontransmission lineconfiguration requirestheunderlying

and adjacent ground and low impedanceplanesto be cleared

near the signal lines.

The exposedthermal paddleis internallyconnected totheground

pin of the amplifier. Solder the paddleto the low impedance

ground plane on the PCB to ensurethe specified electrical

performance and to provide thermal relief. To reduce thermal

impedance further, it is recommended that thegroundplanes

on all layers under the paddlebe connectedtogetherwith vias.

1.30

0.80

0.80

1.30

Figure 57. Recommended PCB Thermal Attach PadDimensions (Millimeters)

0.8 mm

1.3 mm

POWER PLANE

GROUND PLANE

TOP METAL

BOTTOM METAL

Figure 58. Cross-Section of 4-Layer PCB Showing Thermal Via Connection to Buried Ground Plane (Dimensions in Millimeters)