11.1.2 RF Traces and Components

• The RF trace from RFIOP (Pin #5) and RFION (Pin #6) of the ATWILC3000A to the balun must be 50Ω differential controlled impedance. The route from the balun to the antenna connector must be a 50Ω controlled impedance trace. This trace must be routed in reference to the ground plane. This ground reference plane must extend entirely under the ATWILC3000A QFN package and to the sides of the these routes.
• Discuss with the PCB vendor to get the available PCB stack-ups and determine the trace dimensions for achieving 50Ω single-ended controlled impedance.
• Do not have any signal traces below/adjacent to the RF trace in the PCB.
• Be sure that the RF traces from ATWILC3000A to the antenna are as short as possible to reduce path losses and to mitigate the trace from picking up noise.
• Place guard ground vias on either side of the RF trace, running from module to the antenna feed point, in the PCB.
• Do not use thermal relief pads for the ground pads of all components in the RF path. These component pads must be completely filled with GND copper polygon. Place individual vias to the GND pads of these components.
• It is recommended to have a 3x3 grid of ground vias solidly connecting the exposed ground paddle of the ATWILC3000A to the ground plane on the inner/other layers of the PCB. This will act as a good ground and thermal conduction path for the ATWILC3000A.
• Make sure that all digital signals that may be toggling while the ATWILC3000A is active are placed as far away from the antenna as possible.
• Be sure to place the matching components and balun as close to the RFIOP and RFION pins as possible (these are C33, C23, C25, C17, C32, L8 and L9 in the reference schematic). The following figure shows the placement and routing of these components.