APT7846 查看數據表（PDF） - Anpec Electronics

零件编号

产品描述 (功能)

生产厂家

APT7846

Touch Screen Controller

Anpec Electronics 

APT7846

Calculating Touch Resistance

There are total of four measurements possible :

MEASURE

X-position

Y-position

Z1-position

Z2-position

DRIVE

X+,X-

Y+,Y-

Y+,X-

Y+,X-

PIN MEASURED

Y+

X+

X+

Y-

RESULT

A

B

C

D

FIGURE 8 is Pressure measurement diagram.

where the result is a number from 0 to 4096.

From simple network theory , RTHOUCH can be represented in many ways , 2 are given below :

A

D

RTHOUGH = RX * 4096 * (

C

-1 )

where RX = X plate resistance

RX

A

B

or

RTHOUGH = C * 4096 * ( 4096 - C ) - RY + RY * 4096

where RY = Y plate resistance

X+

Y+

Touch

X-Position

X-

Y-

X+

Y+

Touch

Z2-Position

Measure X -Position

Measure Z 1-Position

X+

Y+

Touch

Z1-Position

X-

Y-

X-

Y-

Measure Z 2-Position

FIGURE 8 is Pressure measurement diagram.

Internal Reference

The APT7846 has an internal 2.5V voltage reference

that can be turned ON and OFF with the power-down

address PD1=1(see table V). Typically , the internal

reference voltage is only used in the single-ended

mode for battery monitoring , temperature measure-

ment , and for utilizing the auxiliary input. Optimal

touch-screen performance is achieved when utiliz-

ing the differential mode. The internal reference volt-

age of the APT7846 must be commanded to be off to

maintain compatibility with the APT7843. Therefore ,

after power-up , a write of PD1=0 is required to in-

sure the reference is off.

Copyright  ANPEC Electronics Corp.

10

Rev. A.6 - Dec., 2001

www.anpec.com.tw

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