ADA4930-1/ADA4930-2

Rev. A | Page 23 of 28

LAYOUT, GROUNDING, AND BYPASSING

The ADA4930-1/ADA4930-2 are high speed devices. Realizing

their superior performance requires attention to the details of

high speed PCB design.

The first requirement is to use a multilayer PCB with solid ground

and power planes that cover as much of the board area as possible.

Bypass each power supply pin directly to a nearby ground plane, as

close to the device as possible. Use 0.1 μF high frequency ceramic

chip capacitors.

Provide low frequency bulk bypassing, using 10 μF tantalum

capacitors from each supply to ground.

Stray transmission line capacitance in combination with package

parasitics can potentially form a resonant circuit 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 for complementary signals

to maximize balanced performance.

Figure 56. ADA4930-1 Ground and Power Plane Voiding

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 impedance planes near these pins

(see Figure 56).

If the driver/receiver is more than one-eighth of the wavelength

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

This nontransmission line configuration requires the underlying

and adjacent ground and low impedance planes to be cleared

near the signal lines.

The exposed thermal paddle is internally connected to the ground

pin of the amplifier. Solder the paddle to the low impedance

ground plane on the PCB to ensure the specified electrical

performance and to provide thermal relief. To reduce thermal

impedance further, it is recommended that the ground planes

on all layers under the paddle be connected together with vias.

1.30

0.80

0.80

1.30

Figure 57. Recommended PCB Thermal Attach Pad Dimensions (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)