TYPICAL CHARACTERISTICS
(Cont.)
At T
A
= +25°C, +V
CC
= +2.7V, IOVDD = +1.8V, V
REF
= External +2.5V, 12-bit mode, PD0 = 0, f
SAMPLE
= 125kHz, and f
CLK
= 16 • f
SAMPLE
= 2MHz, unless otherwise noted.
TEMP1 DIODE VOLTAGE vs +V
CC
720
TEMP1 Diode Voltage (mV)
718
716
714
712
710
2.7
3.0
+V
CC
(V)
3.3
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
0.6µm 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
+V
CC
. 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’s on-resistance (if this
is a source of error for the particular measurement).
+2.7V to +5V
1µF
+
to
10µF
(Optional)
TSC2046
B1 +V
CC
C1 +V
CC
D1 X+
E1 Y+
DCLK A2
CS A3
DIN A4
BUSY A5
DOUT A6
PENIRQ B7
IOVDD C7
V
REF
D7
G5
GND
Serial/Conversion Clock
Chip Select
Serial Data In
Converter Status
Serial Data Out
Pen Interrupt
0.1µF
Touch
Screen
To Battery
G2 X–
G3 Y–
G6 V
BAT
Auxiliary Input
E7 AUX
GND
G4
Voltage
Regulator
NOTE: BGA package and pin names shown.
FIGURE 1. Basic Operation of the TSC2046.
8
TSC2046
www.ti.com
SBAS265C
BURR-BROWN [ BURR-BROWN CORPORATION ]
