Use the multi-layer host board for routing signals on the inner layer and the bottom layer.
The top layer (underneath the module) of the host board must be ground with as many GND vias as possible, shown in the following figure.
Avoid fan-out of the signals under the module or antenna area. Use a via to fan-out signals to theedge of the WBZ45 module.
For a better GND connection to the WBZ45 module, solder the exposed GND pads of the WBZ45 module on the host board.
For the module GND pad, use a GND via of a minimum 10 mil (hole diameter) for good ground to all the layers and thermal conduction path.
Having a series resistor on the host board for all GPIOs is recommended. These resistors must be placed close to the WBZ45 module. Refer to the following figure for the placement of the series resistor.
The SOSC crystal (32.768 kHz) on the host board
must be placed close to the WBZ45 module and
follow the shortest trace routing length with no vias (see the following
figure).Figure 4-7. Example of Host Board on
Top Layer
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