MTCH102T-ESLASHST datasheet(9/37 Pages) MICROCHIP

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Preliminary

DS40001793C-page 9

MTCH102/5/8

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 32nd 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

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

Note:

Both R1 and R2 are recommended

to be greater than 100K for lower

power consumption.

10k

VDD

MTSA

10k

VDD

MTSA

10k

MTSA

Host

DAC

Note:

Refer to Application Note “Using PWM to

Generate Analog Output”

(AN538) for

details about how to choose appropriate

R and C values.

MTSA

Host

PWM

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