Hello Pradhan, 1. The distance between the PAD and MCU should be as short as possible to minimize Ctrace, which is a form of parasitic capacitance. Higher parasitic/steady-state/baseline capacitances result in lower sensitivity, therefore making your capacitive touch button signal more difficult to recognize. Separating the PAD and MCU between PCBs is not recommended since it introduces several parasitics including longer trace lengths and pin connectors, hence making the cap touch button less effective. 2. ESD protection for noise immunity is especially important if you are noticing AC load noise on the system that will directly affect the SNR. Series resistors should be placed as closely to the MCU as possible and their value is dependent on factors such as additional ESD protection (TVSs, decoupling capacitors, etc), max IC voltage and current, and so on. More information is supplied by the MSP430 System-Level ESD Considerations Application Report (SLAA530): www.ti.com/.../slaa530.pdf 3. GND pouring should be hatched, spaced as far away, and placed on the layer furthest from the trace lines to reduce parasitic capacitance. Separation between the electrode and coplanar GND pur should be at least one half the height of the covering materials. 4. A circular electrode of about 10 mm in diameter, with an electrode larger than the decal, is recommended for maximum human touch sensing. 5. The PAD should be separated from the surrounding environment with both a soldermask layer and overlay. 6. Circular electrodes are best for human touch. This is all covered in the Capacitive Touch Hardware Design Guide (SLAA576): www.ti.com/.../slaa576a.pdf Regards, Ryan
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