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Layout considerations

Electrical and mechanical design files (symbols, footprints, drawings and step files) are available for download at the support page.

All dimensions are in millimeters, if not specified otherwise.

W-BACnet OEM module pad positions

Refering to the image above. All below positions are with respect to the origin point (0 , 0):

  • Pin P38 position (3.25 , 6)
  • Pin P39 position (10 , 9.25)
  • Pin P40 position (7.1 , 4)
  • Pin P41 position (5.3 , 4)

  • Main pads - oblong 1.4 x 2.79 (oblong edge a half circle with diameter 1.4)
  • Small rectangles left edge 1.0 x 0.8 (red)
  • Small squares right edge 1.02 x 1.02 (blue)
  • Large square 2.0 x 2.0 (green)

Layout considerations for the carrier board

The W-BACnet module has been specifically designed to achieve optimal RF performance. To maintain this, we stress the following guidelines:

  • The use of ground planes on the main board cannot be emphasized enough. Good decoupling of any high-speed digital circuitry is a must. Many embedded microprocessors today have clock frequencies with clocks or overtones that reach well into the GHz range. It is perfectly possible for an embedded design to pass any EMC certification and still cause disturbances that will block the RF reception of the W-BACnet module. The sensitivity of the W-BACnet module receiver is -96 dBm; it is therefore recommended to keep disturbances below -100 dBm in the frequency range of operation.

  • It is essential that all power paths are of low impedance. This means that the power and GND pads must be connected to the source with a sufficient amount of copper (use wide traces and proper via coupling).

  • A near field probe connected to a spectrum analyzer will show if there are any disturbances present on the 2.45 GHz band generated by the microprocessor or any other device that is placed on the main board. Pay special attention to pre-built LAN-products; they pass EMC certifications, but some of them radiate poorly on 2.45 GHz. If disturbances can be seen on a spectrum analyzer - then the W-BACnet module will have impaired reception.

  • The W-BACnet module has supply voltage decoupling on the circuit board. The supply voltage must still be properly filtered. If interference or intermittent communication failures occur, check the supply voltage for dropouts, switch supply ripple, etc.

  • The TOP layer within the footprint must be free of copper. There is a ground plane on the W-BACnet module, but there are also supply lines. It is an unnecessary risk to rely on solder mask lacquer for isolation.

Keep out area Purple diagonal striped area indicates the routing keepout for the top layer. Avoid placing tracks, vias or other copper shapes in this area

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