TSC2003 datasheet(13/22 Pages) TI

13 / 22 page

TSC2003

SBAS162D

www.ti.com

BATTERY MEASUREMENT

An added feature of the TSC2003 is the ability to monitor the

battery voltage on the other side of the voltage regulator

(DC/DC converter), as shown in Figure 7. The battery voltage

can vary from 0.5V to 6V, while the voltage regulator main-

tains the voltage to the TSC2003 at 2.7V, 3.3V, etc. The input

voltage (VBAT1 or VBAT2) is divided down by 4 so that a 6.0V

battery voltage is represented as 1.5V to the A/D converter.

The simplifies the multiplexer and control logic. In order to

minimize the power consumption, the divider is only ON

during the sample period which occurs after control bits C3

= 0, C2 = 0, C1 = 0, and C0 = 1 (VBAT1) or C3 = 0, C2 = 1,

C1 = 0, and C0 = 1 (VBAT2) are received. See Tables I and

II for the relationship between the control bits and configura-

tion of the TSC2003.

VDD

VBAT

7.5k

Ω

2.5k

Ω

DC/DC

Converter

Battery

0.5V

6.0V

0.125V to 1.5V

2.7V

A/D

Converter

FIGURE 7. Battery Measurement Functional Block Diagram.

X-Position

Measure X-Position

Measure Z

1-Position

Touch

X+

Y+

X–

Y–

1-Position

Touch

X+

Y+

Y–

X–

Measure Z

2-Position

Touch

X+

Y+

Y–

X–

FIGURE 8. Pressure Measurement Block Diagrams.

PRESSURE MEASUREMENT

Measuring touch pressure can also be done with the TSC2003.

To determine pen or finger touch, the pressure of the “touch”

needs to be determined. Generally, it is not necessary to

have high accuracy for this test, therefore, the 8-bit resolution

mode is recommended. However, calculations will be shown

with the 12-bit resolution mode. There are several different

ways of performing this measurement—the TSC2003 sup-

ports two methods.

The first method requires knowing the X-Plate resistance,

measurement of the X-Position, and two additional

cross-panel measurements (Z2 and Z1) of the touch screen,

as shown in Figure 8. Using Equation 2 will calculate the

touch resistance:

X Position

4096

– 1

TOUCH

X Plate

=• −













−

(2)

The second method requires knowing both the X-Plate and

Y-Plate resistance, measurement of X-Position and Y-Posi-

tion, and Z1. Equation 3 calculates the touch resistance using

the second method:

Position

4096

– 1

–R

Position

4096

TOUCH

X Plate

Y Plate

−









•

−









−

•

−

1–

(3)

DIGITAL INTERFACE

The TSC2003 supports the I2C serial bus and data transmis-

sion protocol in all three defined modes: standard, fast, and

high-speed. A device that sends data onto the bus is defined

as a transmitter, and a device receiving data as a receiver.

The device that controls the message is called a

master. The

devices that are controlled by the master are

slaves. The bus

must be controlled by a master device which generates the

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