TSC2046

SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008

www.ti.com

9

TYPICAL CHARACTERISTICS (continued)

At TA = +25°C, +VCC = +2.7V, IOVDD = +1.8V, VREF = External +2.5V, 12-bit mode, PD0 = 0, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz,

unless otherwise noted.

TEMP1 DIODE VOLTAGE vs +V

CC

2.7

3.0

3.3

+V

CC (V)

720

718

716

714

712

710

THEORY OF OPERATION

The TSC2046 is a classic successive approximation

register (SAR) analog-to-digital converter (ADC). The

architecture is based on capacitive redistribution, which

inherently includes a sample-and-hold function. The

converter is fabricated on a 0.6

µm CMOS process.

The basic operation of the TSC2046 is shown in Figure 1.

The device features an internal 2.5V reference and uses

an external clock. Operation is maintained from a single

supply of 2.7V to 5.25V. The internal reference can be

overdriven with an external, low-impedance source

between 1V and +VCC. The value of the reference voltage

directly sets the input range of the converter.

The analog input (X-, Y-, and Z-Position coordinates,

auxiliary input, battery voltage, and chip temperature)

to the converter is provided via a multiplexer. A unique

configuration of low on-resistance touch panel driver

switches allows an unselected ADC input channel to

provide power and the accompanying pin to provide

ground for an external device, such as a touch screen.

By maintaining a differential input to the converter and

a differential reference architecture, it is possible to

negate the error from each touch panel driver switch

on-resistance (if this is a source of error for the

particular measurement).

+V

CC

+V

CC

X+

Y+

X

−

Y

−

V

BAT

AUX

B1

C1

D1

E1

G2

G3

G6

E7

G4

G5

A2

A3

A4

A5

A6

B7

C7

D7

DCLK

CS

DIN

BUSY

DOUT

PENIRQ

IOVDD

V

REF

Serial/Conversion Clock

Chip Select

Serial Data In

Converter Status

Serial Data Out

+

1

∝F

to

10

∝F

(Optional)

+2.7V to +5V

TSC2046

Auxiliary Input

To Battery

Voltage

Regulator

Touch

Screen

0.1

∝F

Pen Interrupt

GND

GND

NOTE: VFBGA package and pin names shown.

Figure 1. Basic Operation of the TSC2046