ADA4960-1

Rev. 0 | Page 18 of 20

LAYOUT, GROUNDING, AND BYPASSING

The ADA4960-1 is a high speed device. Realizing its superior

performance requires attention to the details of high speed

printed circuit board (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.

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.

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.

0.3mm DIAMETER VIAS

1.2mm

1.5mm

Figure 44. Recommended PCB Thermal Attach Pad

TOP METAL

GROUND PLANE

POWER PLANE

BOTTOM METAL

1.5mm

1.2mm

Figure 45. Cross-Section of a 4-Layer PCB Showing Thermal Via Connection to Buried Ground Plane