MCP2036-ESLASHP datasheet(8/30 Pages) MICROCHIP

8 / 30 page

MCP2036

DS22186B-page 8

FIGURE 3-2:

Using GPIO for Key Selection (Example)

3.1

Application example

Figure 3-3 shows an example for a 4-key Inductive

Touch keyboard with key controlled by the IO pins of

the PIC® MCU.

FIGURE 3-3:

MCP2036 Typical Application

The PIC® microcontroller is used to generate a square

wave signal and to do all the necessary operations for

proper detection of the key press event.

Then, RIN-CIN filter converts the square wave output of

the PWM into a quasi-triangular waveform.

To calculate the amplitude of the triangular signal, the

standard charging time equation for an RC network will

be used, as shown in Equation 3-1:

EQUATION 3-1:

For the first half of the square wave, the capacitor CIN

is charged through RIN, for the second half, it is

discharged through RIN, and assuming that clock

signal has a 50% duty cycle factor, we can consider:

EQUATION 3-2:

MCP2036

LREF

LBTN

LREF

DRVOUT

10nF

REFSEL

10nF

I/O

CD4052

Key Coils

PIC® Microcontroller

I/O

VDET-

VDETOUT

VDET+

VREF

CLK

DRVIN

PWM

ADC

CFILTER

RGAIN

CRGND

RIN

CIN

RADC

CADC

() V

step

tRC

⁄

–

()

exp

–

[]

•

start

DD 2

⁄ -ΔV

stop

DD 2

⁄ +ΔV

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