MTCH102 Datasheet, PDF (9/37 Pages) Microchip Technology – 2, 5 and 8-Channel Proximity/Touch Controller Data Sheet

3.0 SENSITIVITY ADJUSTMENT
The sensitivity of the sensor inputs determines how far
it can respond to proximity or how much capacitance is
required to activate a touch. The voltage on the
MTCH102/5/8 MTSA pin will determine the sensitivity.
VDD voltage will give the lowest sensitivity, while VSS
voltage will give the highest. The device will sample the
voltage on the MTSA pin after every 32^nd scan, so it
does not only support setting a fixed sensitivity by a
resistor ladder, but it also allows adjusting the
sensitivity dynamically while the device is running. A
Digital-to-Analog Converter (DAC) controlled by the
host or a hardware potentiometer can be used to adjust
the sensitivity. Refer to the typical circuit in Figure 3-1
to Figure 3-4.
FIGURE 3-1:
FIXED SENSITIVITY
USING RESISTOR
LADDER
VDD
R1
R3
MTSA
R2
10k
Note:
Both R1 and R2 are recommended
to be greater than 100K for lower
power consumption.
FIGURE 3-2:
HARDWARE SENSITIVITY
ADJUST USING
POTENTIOMETER
VDD
R2
R1
MTSA
10k
MTCH102/5/8
FIGURE 3-3:
SENSITIVITY
CONTROLLED BY HOST
USING DAC
Host
R2
DAC
10k
MTSA
FIGURE 3-4:
SENSITIVITY
CONTROLLED BY HOST
USING PWM
Host
R
PWM
C
MTSA
Note:
Refer to Application Note “Using PWM to
Generate Analog Output” (AN538) for
details about how to choose appropriate
R and C values.
 2015-2016 Microchip Technology Inc.
Preliminary
DS40001793C-page 9