10.1.2 RF Traces and Components
The RF trace from RFIOP (Pin #7) and RFION (Pin #8) of the ATWINC15x0B 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 ATWINC15x0B QFN package and to the sides of the these routes.
- Determine the available PCB stack-ups and the trace dimensions to achieve 50Ω single-ended controlled impedance.
- Do not have any signal traces below/adjacent to the RF trace in the PCB.
- Ensure that the RF traces from ATWINC15x0B to the antenna is 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 device 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 ATWINC15x0B to the ground plane on the inner/other layers of the PCB. This acts as a good ground and thermal conduction path for the ATWINC15x0B.
- Ensure that all digital signals that may be toggling while the ATWINC15x0B is active are placed as far away from the antenna as possible.
- Ensure that the matching components and balun are placed as close to the RFIOP and RFION pins as possible (C33, C23, C24, C17, C32, L8 and L9 in the reference schematic). The following figure shows the placement and routing of these components.
