Datasheet

 2012 Microchip Technology Inc. Preliminary DS41664A-page 5
MTCH101
3.0 SENSITIVITY ADJUSTMENT
The sensitivity of the system determines how far and
fast it can respond to proximity or touch. The MTCH101
provides the MTSA pin to adjust the sensitivity, and the
voltage on this pin will determine the sensitivity. V
DD
voltage will give the lowest sensitivity, while GND
voltage will give the highest sensitivity.
The device will sample the voltage on the MTSA pin
after each 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. See typical circuit in
Figure 3-1 to Figure 3-4.
FIGURE 3-1: FIXED SENSITIVITY
USING RESISTOR
LADDER
FIGURE 3-2: HARDWARE SENSITIVITY
ADJUST USING
POTENTIOMETER
FIGURE 3-3: SENSITIVITY
CONTROLLED BY HOST
USING DAC
FIGURE 3-4: SENSITIVITY
CONTROLLED BY HOST
USING PWM
MTSA
R3
VDD
10k
Note: Both R1 and R2 are recommended to be
greater than 100K for lower power consumption.
R1
R2
MTSA
R2
VDD
10k
R1
Note 1: Application Note AN538, “Using PWM to
Generate Analog Output”
has details
about how to choose appropriate R and C
values.
MTSA
R2
10k
Host
DAC
MTSA
R
Host
PWM
C