MTCH101 Datasheet, PDF (5/20 Pages) Microchip Technology – Single-Channel Proximity Detector

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. VDD
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:
VDD
FIXED SENSITIVITY
USING RESISTOR
LADDER
R1
R3
MTSA
10k
R2
MTCH101
FIGURE 3-3:
SENSITIVITY
CONTROLLED BY HOST
USING DAC
Host
R2
DAC
1 0k
MTSA
FIGURE 3-4:
SENSITIVITY
CONTROLLED BY HOST
USING PWM
Host
R
PWM
C
MTSA
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
Note 1: Application Note AN538, “Using PWM to
Generate Analog Output” has details
about how to choose appropriate R and C
values.
R2
R1
10k
MTSA
 2012-2013 Microchip Technology Inc.
Preliminary
DS40001664B-page 5