Datasheet

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SBAS417B − JUNE 2007 − REVISED JANUARY 2008
www.ti.com
9
TYPICAL CHARACTERISTICS (continued)
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
2.7 3.0 3.3
+V
CC
(V)
TEMP1 Diode Voltage (mV)
720
718
716
714
712
710
THEORY OF OPERATION
The TSC2046E 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 TSC2046E 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
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
µ
F
to
10
µ
F
(Optional)
+2.7V to +5V
TSC2046E
Auxiliary Input
To Battery
Voltage
Regulator
Touch
Screen
0.1
µ
F
Pen Interrupt
GND
GND
NOTE: VFBGA package and pin names shown.
Figure 1. Basic Operation of the TSC2046E