TSC2004 datasheet(18/62 Pages) TI2

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ANALOG-TO-DIGITAL CONVERTER

Converter

-REF

+REF

+IN

-IN

AUX

SNSGND

AGND

X+

X-

SNSVDD

PenTouch

IRQ

(1)

50kW

Y+

Y-

VREF

PINTDAV

Preprocessing

Zone

Detect

Control

Logic

LevelShift

Data

Available

C3-C0

MAV

SNSVDD

AGND

TSC2004

SBAS408E – JUNE 2007 – REVISED MARCH 2008

Figure 28 shows the analog inputs of the TSC2004. The analog inputs (X, Y, and Z touch panel coordinates, chip

temperature and auxiliary inputs) are provided via a multiplexer to the Successive Approximation Register (SAR)

Analog-to-Digital (A/D) converter. The A/D architecture is based on capacitive redistribution architecture, which

inherently includes a sample-and-hold function.

(1)

Untrimmed resistor; see the typical value in the Electrical Characteristics

Figure 28. Simplified Diagram of the Analog Input Section

A unique configuration of low on-resistance switches allows an unselected A/D converter input channel to

provide power and an accompanying pin to provide ground for driving the touch panel. By maintaining a

differential input to the converter and a differential reference input architecture, it is possible to negate errors

caused by the driver switch on-resistances.

The A/D converter is controlled by two A/D Converter Control registers. Several modes of operation are possible,

depending on the bits set in the control registers. Channel selection, scan operation, preprocessing, resolution,

and conversion rate may all be programmed through these registers. These modes are outlined in the sections

that follow for each type of analog input. The conversion results are stored in the appropriate result register.

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