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WA_DEV_W218_PTS_002 Rev 005 Page 94 of 109
Product Technical Specification &
Customer Design Guidelines
Note 1
: Please refer to the recommendations specified in the Pin Description sub-section regarding the connection between
DSR and DTR.
PCB Specification for Application Board
In order to save costs for simple applications, a cheap PCB structure can be used for the application
board of the WISMO218. A 4-layer through-hole type PCB structure can be used.
Figure 44. PCB Structure Example for the Application Board
Note: Due to the limited layers of 4-layer PCBs, sensitive signals like audio, SIM and clocks cannot be
protected by 2 adjacent ground layers. As a result, during PCB layout, care must be taken for these
sensitive signals, by avoiding coupling to noisy baseband through adjacent layers.