CapSense Technology
CY8C20xx7/S CapSense
®
Design Guide
Doc. No. 001-78329 Rev. *E
19
Figure 2-13. Design of Laptop Multimedia Keys for a 21-Inch Model
Figure 2-14. Design of Laptop Multimedia Keys for a 15-Inch Model with Identical Functionality and Button Size
2.2.3.2 Reduced Design Cycle Time
Usually, the most time-consuming task for a capacitive sensor interface design is firmware development and sensor
tuning. With a typical touch-sensing controller, the sensor must be retuned when the same design is ported to
different models or when there are changes in the mechanical dimensions of the PCB or the sensor PCB layout. A
design with SmartSense_EMCPLUS solves these challenges because it needs less firmware development effort, no
tuning, and no retuning. This makes a typical design cycle much faster.
compares the design cycles of a
typical touch-sensing controller and a SmartSense_EMC_PLUS-based design.
Figure 2-15. Typical Capacitive Interface Design Cycle Comparison
Feasibility
Study
Schematics
Design
PCB Layout
Design
Mechanical Design
Review
System
Integration
Re-tuning for any
changes
Tuning process
Production Fine
Tuning
Design
Validation
Production
Typical Capacitive User Interface Design Cycle
Firmware
Development
Feasibility
Study
Schematics
Design
PCB Layout
Design
Mechanical Design
Review
System
Integration
Design
Validation
Production
SmartSense-based Capacitive User Interface Design Cycle
Firmware
Development
2.2.4 Selecting the User Module
The SmartSense_EMCPLUS eliminates the tuning process that is required by CSD and CSDPLUS UM. It is
recommended to use SmartSense_EMCPLUS to simplify the CapSense design process. However, there may be
instances where the sensor parameters such as resolution and prescaler need to be controlled to optimize device
power consumption or detect touch for a sensor with high C
P
. In such cases, use the CSD/CSDPLUS UM.
The following are the advantages of the CSDPLUS UM when compared to CSD:
CSDPLUS UM provides higher
for a given sensor resolution (or scan time).
CSDPLUS UM requires less time to scan a sensor to achieve the same SNR. Because of the short scan time,
the average power consumption
a
of the CapSense device with CSDPLUS UM will be lower than the CSD UM
when they are tuned to achieve the same SNR.
However, if the sensor C
P
is below 10 pF, the CSDPLUS UM provides lower SNR when compared to the CSD UM
and it is recommended to use the CSD UM instead of the CSDPLUS UM.
Note:
When I
COMP
is set to
„0‟, the CSDPLUS UM behavior will be the same as the CSD UM.
a
Here the device is assumed to enter sleep mode after scanning the sensor and wakeup periodically to reduce the device power
consumption.
