Glossary
AN66308 - CY8CMBR2044 CapSense® Design Guide, Doc. No. 001-66308 Rev. *F
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While designing a PCB for capacitive sensing, a grounded copper plane should be placed surrounding
the sensors for good noise immunity. But a solid ground increases the parasitic capacitance of the sensor
which is not desired. Therefore, the ground should be filled in a special hatch pattern. A hatch pattern has
closely-placed, crisscrossed lines looking like a mesh and the line width and the spacing between two
lines determine the fill percentage. In case of liquid tolerance, this hatch fill referred as a shield electrode
is driven with a shield signal instead of ground.
Hysteresis
A parameter used to prevent the sensor status output from random toggling due to system noise, used in
conjunction with the Finger Threshold to determine the sensor state. See
IDAC (Current-Output Digital-to-Analog Converter)
Programmable constant current source available inside PSoC, used for CapSense and ADC operations.
Liquid Tolerance
The ability of a capacitive sensing system to work reliably in the presence of liquid droplets, streaming
liquids or mist.
Linear Slider
A widget consisting of more than one sensor arranged in a specific linear fashion to detect the physical
position (in single axis) of a finger.
Low Baseline Reset
A parameter that represents the maximum number of scan samples where the Raw Count is abnormally
below the Negative Noise Threshold. If the Low Baseline Reset value is exceeded, the Baseline is reset
to the current Raw Count.
Manual-Tuning
The manual process of setting (or tuning) the CapSense parameters.
Matrix Buttons
A widget consisting of more than two sensors arranged in a matrix fashion, used to detect the presence
or absence of a human finger (a touch) on the intersections of vertically and horizontally arranged
sensors.
If M is the number of sensors on the horizontal axis and N is the number of sensors on the vertical axis,
the Matrix Buttons Widget can monitor a total of M x N intersections using ONLY M + N port pins.
When using the CSD sensing method (self-capacitance), this Widget can detect a valid touch on only one
intersection position at a time.
Modulation Capacitor (CMOD)
An external capacitor required for the operation of a CSD block in Self-Capacitance sensing mode.
Modulator Clock
A clock source that is used to sample the modulator output from a CSD block during a sensor scan. This
clock is also fed to the Raw Count counter. The scan time (excluding pre and post processing times) is
given by (2
N
– 1)/Modulator Clock Frequency, where N is the Scan Resolution.
Modulation IDAC
