Design Considerations
AN64846 - Getting Started with CapSense
®
Doc. No. 001-64846 Rev. *X
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3.6 Proximity Sensing Design
This section presents the steps involved in implementing a proximity sensor and the various factors that affect the
proximity distance. For the detailed design guidelines, refer to
– Proximity Sensing with CapSense
3.6.1 Implementing Proximity Sensing with CapSense
shows the steps for designing a proximity-sensing system based on CapSense.
1.
Understand proximity sensing:
section in this design guide explains how proximity
sensing, based on CapSense, works and describes the parameters that affect proximity-sensing distance.
2.
Evaluate how proximity sensing works:
3.
Specify the proximity-sensing requirements:
After evaluating the proximity sensor performance, specify the
proximity-sensing requirements such as the required proximity-sensing distance, area available on the PCB for
sensor construction, system power consumption requirements, and EMI/ESD performance. These requirements
help you to select the right CapSense device and design the sensor layout.
4.
Select the right CapSense device:
After the requirements are finalized, refer to the
chapter to select the right CapSense device based on the required proximity-sensing distance.
5.
Design the schematic and layout:
After selecting the CapSense device, design the schematic and layout. Follow
the guidelines mentioned in the
section to design the schematic. You should also refer to the
device datasheet and device-specific
for details on the schematic design. For proximity-
sensor layout guidelines such as proximity-sensor type and size, refer to the section
Factors Affecting Proximity Distance
6.
Build the prototype:
After the schematic and layout design is completed, build the prototype of the design to
check if the design meets the performance requirements.
7.
Tune:
Tune the prototype board to achieve the required performance. See the
After tuning the sensor, check if the proximity sensor performance meets the requirements. If the requirements are
met, proceed to step 11; otherwise continue with Step 8.
8.
Redesign if necessary:
If the proximity sensor does not provide the required performance after you have set the
optimum parameters, increase the sensor size or reduce the noise in the system by shielding the sensor from
noise sources and continue with Step 9.
9.
Retune:
After redesigning the proximity sensor, retune the sensor and check if the sensor performance meets the
requirements. If the requirements are met, proceed to Step 11; otherwise continue with Step 10.
10.
Revisit the design or requirements:
If the proximity sensor does not meet the required performance even after
you have changed the sensor dimensions to the maximum possible value and tuned it with the optimum
parameters, revisit the requirements.
If you are not able to achieve the required proximity-sensing distance, select a device that has a better proximity
performance than the current device.
If you are not able to achieve the required proximity-sensing distance even with the best device, you need to
change the proximity sensor requirements, such as the area available for the sensor or the required proximity-
sensing distance, and repeat the procedure from Step 1.
11.
Proceed to mass production:
If the proximity sensor meets the required performance, you can proceed to mass
production.
