3 Replies Latest reply on Mar 22, 2017 7:41 AM by MichaelF_56

    BCM20736S layout instructions?

    marco.belcastro

      Hi,

      I'm trying to understand how to layout this IC so that I get the best range possible but the instructions on the technical manual are nor very clear to me.MWSnap 2017-03-21, 12_45_26.jpg

      Are side A and D on the edge of the board or is the GND Plane on the edge of the board? If the GND plane is not the edge of the board then what should I do after that? Can I just extend this GND plane for the entire board?

      Where there is the L indication for the GND plane the same does nor reach the edge of the keepout area. Why is that? What should be placed above this area?

      Would someone have an example that has a good range with this IC (no external antenna)?

        • 1. Re: BCM20736S layout instructions?
          BoonT_56

          Firstly, the above picture is the layout recommendation of the 20737S SiP module. This module has packaged the IC, filter, crystal, EEPROM and antenna altogether under one roof.

           

          Side A can be near to the edge of the motherboard.

           

          The purpose of the L-shaped ground plane is to maximize the antenna efficiency (up to 40% with a maximum usable range of 50m) of the embedded antenna. Deviations will result in the reduction of range, but it may be acceptable to some as they need probably only 10m. It can sit on the top layer or underneath. Below is a picture of a top-only layout and do take note there are no component on the ground plane.

           

          20732S.jpg

           

          Otherwise, you may lay the ground in a two-layer arrangement as shown below. The picture were extracted from an actual layout and I think it offered a better view.

           

          (1) Top layer (in blue)

          top.jpg

           

          (2) Second layer (in purple)

           

          bottom.jpg

           

          More details at here:

           

          Sample BCM20732S PCB Layout

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          • 2. Re: BCM20736S layout instructions?
            marco.belcastro

            On the top layer in blue there is a trace coming out from the corner (it is a GND trace) but the datasheet clearly states

            • Connect to system ground from side D of the module (pins 13–22).
            • Route signal traces out of the module from side C (between pins 27 and 30) or side D (between pins 16 and 19) of the module. Traces can be overlapped to avoid routing through the keep-out area.

            In our previous designs we implemented the layout exactly as descried by you plus we respected the above two points but we never get more than 10m. Is there a more detailed description on how to do the layout? The information given on the documentation is not clear for such an important aspect of the design witch is the RF requirements.

            • 3. Re: BCM20736S layout instructions?
              MichaelF_56

              WICED Sense 1 and 2 use the SiP module.

               

              Here's the WICED Sense 2 PCB Files

               

              These may be useful to extract exact layout requirements.