Low Voltage I/O Touch Screen Controller (Rev. G)

Low Voltage I/O Touch Screen Controller (Rev. G)
TSC2046
SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
Low-Voltage I/O
TOUCH SCREEN CONTROLLER
FEATURES
D
D
D
D
D
D
D
D
D
D
DESCRIPTION
SAME PINOUT AS ADS7846
2.2V TO 5.25V OPERATION
1.5V TO 5.25V DIGITAL I/O
INTERNAL 2.5V REFERENCE
DIRECT BATTERY MEASUREMENT (0V TO 6V)
ON-CHIP TEMPERATURE MEASUREMENT
TOUCH-PRESSURE MEASUREMENT
QSPI AND SPI 3-WIRE INTERFACE
AUTO POWER-DOWN
AVAILABLE IN TSSOP-16, QFN-16, AND
VFBGA-48 PACKAGES
APPLICATIONS
D
D
D
D
D
D
The TSC2046 is a next-generation version to the
ADS7846 4-wire touch screen controller which supports
a low-voltage I/O interface from 1.5V to 5.25V. The
TSC2046 is 100% pin-compatible with the existing
ADS7846, and will drop into the same socket. This allows
for easy upgrade of current applications to the new
version. The TSC2046 also has an on-chip 2.5V
reference that can be used for the auxiliary input, battery
monitor, and temperature measurement modes. The
reference can also be powered down when not used to
conserve power. The internal reference operates down to
2.7V supply voltage, while monitoring the battery voltage
from 0V to 6V.
The low power consumption of < 0.75mW typ at 2.7V
(reference off), high-speed (up to 125kHz sample rate),
and on-chip drivers make the TSC2046 an ideal choice for
battery-operated systems such as personal digital
assistants (PDAs) with resistive touch screens, pagers,
cellular phones, and other portable equipment. The
TSC2046 is available in TSSOP-16, QFN-16, and
VFBGA-48 packages and is specified over the –40°C to
+85°C temperature range.
PERSONAL DIGITAL ASSISTANTS
PORTABLE INSTRUMENTS
POINT-OF-SALE TERMINALS
PAGERS
TOUCH SCREEN MONITORS
CELLULAR PHONES
US Patent No. 6246394
QSPI and SPI are registered trademarks of Motorola.
PENIRQ
Pen Detect
+VCC
X+
Temperature
Sensor
X−
SAR
IOVDD
Y+
DOUT
TSC2046
Y−
BUSY
Comparator
6− Channel
MUX
VBAT
CDAC
Serial
Data
In/Out
CS
DCLK
Battery
Monitor
DIN
AUX
VREF
Internal 2.5V Reference
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
Copyright  2002−2008, Texas Instruments Incorporated
! ! www.ti.com
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
ABSOLUTE MAXIMUM RATINGS(1)
ELECTROSTATIC DISCHARGE SENSITIVITY
+VCC and IOVDD to GND . . . . . . . . . . . . . . . . . . . . . −0.3V to +6V
Analog Inputs to GND . . . . . . . . . . . . . . . . . −0.3V to +VCC + 0.3V
Digital Inputs to GND . . . . . . . . . . . . . . . . . −0.3V to IOVDD + 0.3V
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250mW
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . +150°C
Operating Temperature Range . . . . . . . . . . . . . . . . −40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . . . . . . −65°C to +150°C
Lead Temperature (soldering, 10s) . . . . . . . . . . . . . . . . . . . . . +300°C
(1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods
may degrade device reliability. These are stress ratings only, and
functional operation of the device at these or any other conditions
beyond those specified is not implied.
This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be
handled with appropriate precautions. Failure to observe
proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to
complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
PACKAGE/ORDERING INFORMATION(1)
PRODUCT
TSC2046I
NOMINAL
PENIRQ
PULLUP
RESISTOR
VALUES
50kΩ
MAXIMUM
INTEGRAL
LINEARITY
ERROR
(LSB)
±2
PACKAGELEAD
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
TSSOP-16
PW
−40°C to +85°C
TSC2046I
4x4, 1mm
QFN-16
4x4
VFBGA-48
TSC2046I(2)
(1)
90kΩ
±2
4x4
VFBGA-48
RGV
−40°C
−40
C to +85
+85°C
C
TSC2046
GQC
−40°C to +85°C
AZ2046
ZQC
−40°C to +85°C
BC2046
GQC
−40°C to +85°C
ZQC
−40°C to +85°C
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
TSC2046IPW
Rails, 100
TSC2046IPWR
Tape and Reel, 2500
TSC2046IRGVT
Tape and Reel, 250
TSC2046IRGVR
Tape and Reel, 2500
TSC2046IRGVRG4
Tape and Reel, 2500
TSC2046IGQCR
Tape and Reel, 2500
TSC2046IZQCT
Tape and Reel, 250
TSC2046IZQCR
Tape and Reel, 2500
AZ2046A
TSC2046IGQCR-90
Tape and Reel, 2500
BC2046A
TSC2046IZQCR-90
Tape and Reel, 2500
For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet, or see the TI web
site at www.ti.com.
(2) High-impedance version.
2
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V
At TA = −40°C to +85°C, +VCC = +2.7V, VREF = 2.5V internal voltage, fSAMPLE = 125kHz, fCLK = 16 • fSAMPLE = 2MHz, 12-bit mode, digital
inputs = GND or IOVDD, and +VCC must be ≥ IOVDD, unless otherwise noted.
PARAMETER
ANALOG INPUT
Full-Scale Input Span
Absolute Input Range
CONDITION
MIN
Positive Input−Negative Input
Positive Input
Negative Input
0
−0.2
−0.2
Capacitance
Leakage Current
SYSTEM PERFORMANCE
Resolution
No Missing Codes
Integral Linearity Error
Offset Error
Gain Error
Noise
Power-Supply Rejection
SAMPLING DYNAMICS
Conversion Time
Acquisition Time
Throughput Rate
Multiplexer Settling Time
Aperture Delay
Aperture Jitter
Channel-to-Channel Isolation
SWITCH DRIVERS
On-Resistance
Y+, X+
Y−, X−
Drive Current(2)
BATTERY MONITOR
Input Voltage Range
Input Impedance
Sampling Battery
Battery Monitor Off
Accuracy
TEMPERATURE MEASUREMENT
Temperature Range
Resolution
Accuracy
(1)
(2)
(3)
(4)
(5)
(6)
(7)
MAX
UNITS
VREF
+VCC + 0.2
+0.2
V
V
V
pF
µA
25
0.1
12
11
±2
±6
±4
External VREF
Including Internal VREF
70
70
12
3
125
500
30
100
100
VIN = 2.5VPP at 50kHz
5
6
Duration 100ms
REFERENCE OUTPUT
Internal Reference Voltage
Internal Reference Drift
Quiescent Current
REFERENCE INPUT
Range
Input Impedance
TSC2046
TYP
50
2.45
2.50
15
500
Ω
Ω
mA
+VCC
1
V
GΩ
250
Ω
6.0
V
+2
+3
kΩ
GΩ
%
%
10
1
−2
−3
−40
Differential Method(3)
TEMP0(4)
Differential Method(3)
TEMP0(4)
CLK Cycles
CLK Cycles
kHz
ns
ns
ps
dB
V
ppm/°C
µA
0.5
VBAT = 0.5V to 5.5V, External VREF = 2.5V
VBAT = 0.5V to 5.5V, Internal Reference
LSB
LSB
µVrms
dB
2.55
1.0
SER/DFR = 0, PD1 = 0
Internal Reference Off
Internal Reference On
Bits
Bits
LSB(1)
+85
1.6
0.3
±2
±3
°C
°C
°C
°C
°C
LSB means Least Significant Bit. With VREF = +2.5V, one LSB is 610µV.
Assured by design, but not tested. Exceeding 50mA source current may result in device degradation.
Difference between TEMP0 and TEMP1 measurement, no calibration necessary.
Temperature drift is −2.1mV/°C.
TSC2046 operates down to 2.2V.
IOVDD must be ≤ (+VCC).
Combined supply current from +VCC and IOVDD. Typical values obtained from conversions on AUX input with PD0 = 0.
3
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V (continued)
At TA = −40°C to +85°C, +VCC = +2.7V, VREF = 2.5V internal voltage, fSAMPLE = 125kHz, fCLK = 16 • fSAMPLE = 2MHz, 12-bit mode, digital
inputs = GND or IOVDD, and +VCC must be ≥ IOVDD, unless otherwise noted.
PARAMETER
DIGITAL INPUT/OUTPUT
Logic Family
Capacitance
VIH
VIL
VOH
VOL
CONDITION
All Digital Control Input Pins
| IIH | ≤ +5µA
| IIL | ≤ +5µA
IOH = −250µA
IOL = 250µA
MIN
CMOS
5
IOVDD • 0.7
−0.3
IOVDD • 0.8
IOVDD(6)
Quiescent Current(7)
Power Dissipation
TEMPERATURE RANGE
Specified Performance
(1)
(2)
(3)
(4)
(5)
(6)
(7)
4
MAX
UNITS
15
IOVDD + 0.3
0.3 • IOVDD
pF
V
V
V
V
0.4
Straight
Binary
Data Format
POWER-SUPPLY REQUIREMENTS
+VCC(5)
TSC2046
TYP
Specified Performance
Operating Range
2.7
2.2
1.5
Internal Reference Off
Internal Reference On
fSAMPLE = 12.5kHz
Power-Down Mode with
CS = DCLK = DIN = IOVDD
+VCC = +2.7V
280
780
220
−40
LSB means Least Significant Bit. With VREF = +2.5V, one LSB is 610µV.
Assured by design, but not tested. Exceeding 50mA source current may result in device degradation.
Difference between TEMP0 and TEMP1 measurement, no calibration necessary.
Temperature drift is −2.1mV/°C.
TSC2046 operates down to 2.2V.
IOVDD must be ≤ (+VCC).
Combined supply current from +VCC and IOVDD. Typical values obtained from conversions on AUX input with PD0 = 0.
3.6
5.25
+VCC
650
3
V
V
V
µA
µA
µA
µA
1.8
mW
+85
°C
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
PIN CONFIGURATION
Top View
Top View
TSSOP
VFBGA
DCLK
1
+VCC
1
16
DCLK
X+
2
15
CS
Y+
3
14
DIN
X−
4
Y−
5
GND
13
TSC2046
2
DIN
3
BUSY DOUT
4
5
6
7
A NC
+VCC
DOUT
6
11
PENIRQ
VBAT
7
10
IOVDD
AUX
8
NC
B
NC
C
NC
D
NC
E
F NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
PENIRQ
+VCC
BUSY
12
IOVDD
X+
VREF
Y+
9
CS
AUX
NC
VREF
G NC
NC
GND
GND
VBAT
13 VREF
8
X−
4
(Thermal Pad)(1)
7
DCLK
3
Y+
CS
TSC2046
6
2
X+
DIN
5
1
Y−
QFN
+VCC
BUSY
14 IOVDD
16 DOUT
Top View
15 PENIRQ
X−
12
AUX
11
VBAT
10
GND
9
Y−
(1) The thermal pad is internally connected to the substrate. This pad can be connected to the analog ground or left floating. Keep the thermal
pad separate from the digital ground, if possible.
PIN DESCRIPTION
TSSOP PIN #
QFN PIN #
NAME
DESCRIPTION
1
VFBGA PIN #
B1 and C1
5
Power Supply
2
D1
6
+VCC
X+
3
E1
7
Y+
Y+ Position Input
4
G2
8
X−
X− Position Input
5
G3
9
Y−
Y− Position Input
6
G4 and G5
10
GND
Ground
7
G6
11
Battery Monitor Input
8
E7
12
VBAT
AUX
9
D7
13
10
C7
14
VREF
IOVDD
11
B7
15
PENIRQ
12
A6
16
DOUT
Serial Data Output. Data are shifted on the falling edge of DCLK. This output is high
impedance when CS is high.
13
A5
1
BUSY
Busy Output. This output is high impedance when CS is high.
14
A4
2
DIN
Serial Data Input. If CS is low, data are latched on the rising edge of DCLK.
15
A3
3
CS
Chip Select Input. Controls conversion timing and enables the serial input/output register.
CS high = power-down mode (ADC only).
16
A2
4
DCLK
X+ Position Input
Auxiliary Input to ADC
Voltage Reference Input/Output
Digital I/O Power Supply
Pen Interrupt
External Clock Input. This clock runs the SAR conversion process and synchronizes serial
data I/O.
5
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
TYPICAL CHARACTERISTICS
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.
+VCC SUPPLY CURRENT vs TEMPERATURE
IOVDD SUPPLY CURRENT vs TEMPERATURE
30
350
IOVDD Supply Current (µA)
+VCC Supply Current (µA)
400
300
250
200
150
100
−40
−20
0
20
40
60
80
25
20
15
10
5
−40
100
−20
Temperature (°C)
0
20
40
60
80
100
4.5
5.0
4.5
5.0
Temperature (°C)
+VCC SUPPLY CURRENT vs +VCC
POWER−DOWN SUPPLY CURRENT vs TEMPERATURE
450
140
400
+VCC Supply Current (µA)
Supply Current (nA)
120
100
80
60
40
fSAMPLE = 125kHz
350
300
250
200
f SAMPLE = 12.5kHz
150
100
−40
−20
0
20
40
60
80
2.0
100
2.5
3.0
1M
+VCC ≥ IOVDD
50
Sample Rate (Hz)
IOVDD Supply Current (µA)
4.0
MAXIMUM SAMPLE RATE vs +VCC
IOVDD SUPPLY CURRENT vs IOVDD
60
40
fSAMPLE = 125kHz
30
20
10
100k
10k
fSAMPLE = 12.5kHz
0
1k
1.0
1.5
2.0
2.5
3.0
IOVDD (V)
6
3.5
+VCC (V)
Temperature (°C)
3.5
4.0
4.5
5.0
2.0
2.5
3.0
3.5
+VCC (V)
4.0
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
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.
CHANGE IN OFFSET vs TEMPERATURE
0.10
0.4
Delta from +25°C (LSB)
0.6
0.05
0
−0.05
−0.10
−0.15
−40
−20
0
20
40
60
80
0.2
0
−0.2
−0.4
−0.6
−40
100
−20
0
Temperature (°C)
40
60
80
100
REFERENCE CURRENT vs TEMPERATURE
14
18
12
16
Reference Current (µA)
Reference Current (µA)
20
Temperature (°C)
REFERENCE CURRENT vs SAMPLE RATE
10
8
6
4
14
12
10
8
2
0
0
25
50
75
100
6
−40
125
−20
0
20
40
60
80
100
Temperature (°C)
Sample Rate (kHz)
SWITCH ON− RESISTANCE vs +VCC
(X+, Y+: +VCC to Pin; X−, Y−: Pin to GND)
SWITCH ON−RESISTANCE vs TEMPERATURE
(X+, Y+: +VCC to Pin; X−, Y−: Pin to GND)
8
8
Y−
7
7
Y−
6
6
5
RON (Ω)
RON (Ω)
Delta from +25°C (LSB)
CHANGE IN GAIN vs TEMPERATURE
0.15
X−
X+, Y+
5
X−
4
3
X+, Y+
4
2
1
3
2.0
2.5
3.0
3.5
+VCC (V)
4.0
4.5
5.0
−40
−20
0
20
40
60
80
100
Temperature (°C)
7
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
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.
INTERNAL VREF vs TEMPERATURE
MAXIMUM SAMPLING RATE vs RIN
2.5080
2.5075
INL: RIN = 500Ω
INL: RIN = 2kΩ
DNL: RIN = 500Ω
DNL: RIN = 2kΩ
1.8
1.6
1.4
2.5070
Internal VREF (V)
Max Absolute Delta Error from
RIN = 0 (LSB)
2.0
1.2
1.0
0.8
0.6
2.5065
2.5060
3.5055
2.5050
2.5045
2.5040
0.4
2.5035
0.2
2.5030
20
40
60
80
100 120 140
Sampling Rate (kHz)
160
180
−40
−35
−30
−25
−20
−15
−10
−5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
0
200
Temperature (°C)
INTERNAL VREF vs +VCC
INTERNAL VREF vs TURN− ON TIME
2.510
100
No Cap
(42µs)
12-Bit Settling
80
2.500
Internal VREF (%)
Internal VREF (V)
2.505
2.495
2.490
1µF Cap
(124µs)
12-Bit Settling
60
40
20
2.485
2.480
0
2.5
3.0
3.5
4.0
4.5
5.0
0
+VCC (V)
200
400
600
800
1000
1200
1400
Turn-On Time (µs)
TEMP DIODE VOLTAGE vs TEMPERATURE
TEMP0 DIODE VOLTAGE vs +VCC
850
604
750
90.1mV
TEMP1
700
650
600
550
TEMP0
135.1mV
500
450
602
600
598
596
−40
−35
−30
−25
−20
−15
−10
−5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
594
Temperature (°C)
8
TEMP0 Diode Voltage (mV)
TEMP Diode Voltage (mV)
800
2.7
3.0
+VCC (V)
3.3
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
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 +VCC
TEMP1 Diode Voltage (mV)
720
718
716
714
712
710
2.7
3.0
3.3
+VCC (V)
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 +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).
+2.7V to +5V
1∝F
+
to
10∝F
(Optional)
Touch
Screen
0.1∝F
TSC2046
B1 +VCC
DCLK A2
C1 +VCC
CS A3
Serial/Conversion Clock
Chip Select
Serial Data In
D1 X+
DIN A4
E1 Y+
BUSY A5
Converter Status
G2 X−
DOUT A6
Serial Data Out
G3 Y−
PENIRQ B7
Pen Interrupt
To Battery
Auxiliary Input
Voltage
Regulator
G6 VBAT
IOVDD C7
E7 AUX
VREF D7
GND G4
G5 GND
NOTE: VFBGA package and pin names shown.
Figure 1. Basic Operation of the TSC2046
9
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
ANALOG INPUT
When the converter enters the hold mode, the voltage
difference between the +IN and –IN inputs (shown in
Figure 2) is captured on the internal capacitor array. The
input current into the analog inputs depends on the
conversion rate of the device. During the sample period, the
source must charge the internal sampling capacitor (typically
25pF). After the capacitor is fully charged, there is no further
input current. The rate of charge transfer from the analog
source to the converter is a function of conversion rate.
Figure 2 shows a block diagram of the input multiplexer on
the TSC2046, the differential input of the ADC, and the
differential reference of the converter. Table 1 and Table 2
show the relationship between the A2, A1, A0, and
SER/DFR control bits and the configuration of the TSC2046.
The control bits are provided serially via the DIN pin—see the
Digital Interface section of this data sheet for more details.
+VCC
PENIRQ IOVDD
Level
Shifter
TEMP1
50kΩ
or
90kΩ
VREF
TEMP0
Logic
A2− A0
(Shown 001B)
SER/DFR
(Shown Low)
X+
X−
Ref On/Off
Y+
+IN
Y−
+REF
ADC
−IN
2.5V
Reference
−REF
7.5kΩ
VBAT
2.5kΩ
Battery
On
AUX
GND
Figure 2. Simplified Diagram of Analog Input
A2
A1
A0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
VBAT
AUXIN
TEMP
Y−
X+
Y+
+IN (TEMP0)
Y-POSITION X-POSITION Z1-POSITION Z2-POSITION X-DRIVERS
Off
+IN
Measure
Off
+IN
+IN
Measure
+IN
Measure
+IN
Measure
+IN
+IN (TEMP1)
Y-DRIVERS
Off
On
Off
Off
X−, On
Y+, On
X−, On
Y+, On
On
Off
Off
Off
Off
Off
Table 1. Input Configuration (DIN), Single-Ended Reference Mode (SER/DFR high)
A2
A1
A0
+REF
−REF
0
0
1
Y+
Y−
Y−
+IN
X+
0
1
1
Y+
X−
+IN
1
0
0
Y+
X−
1
0
1
X+
X−
Y+
Y-POSITION
X-POSITION
Z1-POSITION
Z2-POSITION
Measure
Y+, Y−
Measure
+IN
Y+, X−
Measure
+IN
Measure
Table 2. Input Configuration (DIN), Differential Reference Mode (SER/DFR low)
10
DRIVERS
Y+, X−
X+, X−
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INTERNAL REFERENCE
The TSC2046 has an internal 2.5V voltage reference that
can be turned on or off with the control bit, PD1 (see Table 5
and Figure 3). Typically, the internal reference voltage is only
used in the single-ended mode for battery monitoring,
temperature measurement, and for using the auxiliary input.
Optimal touch screen performance is achieved when using
the differential mode. The internal reference voltage of the
TSC2046 must be commanded to be off to maintain
compatibility with the ADS7843. Therefore, after power-up,
a write of PD1 = 0 is required to insure the reference is off
(see the Typical Characteristics for power-up time of the
reference from power-down).
Reference
Power−Down
Band
Gap
There is also a critical item regarding the reference when
making measurements while the switch drivers are ON. For
this discussion, it is useful to consider the basic operation of
the TSC2046 (see Figure 1). This particular application
shows the device being used to digitize a resistive touch
screen. A measurement of the current Y-Position of the
pointing device is made by connecting the X+ input to the
ADC, turning on the Y+ and Y– drivers, and digitizing the
voltage on X+ (Figure 4 shows a block diagram). For this
measurement, the resistance in the X+ lead does not affect
the conversion (it does affect the settling time, but the
resistance is usually small enough that this is not a concern).
However, since the resistance between Y+ and Y– is fairly
low, the on-resistance of the Y drivers does make a small
difference. Under the situation outlined so far, it is not
possible to achieve a 0V input or a full-scale input regardless
of where the pointing device is on the touch screen because
some voltage is lost across the internal switches. In addition,
the internal switch resistance is unlikely to track the
resistance of the touch screen, providing an additional
source of error.
VREF
Buffer
+VCC
To
CDAC
VREF
Optional
Y+
Figure 3. Simplified Diagram of the Internal
Reference
X+
REFERENCE INPUT
The voltage difference between +REF and –REF (see
Figure 2) sets the analog input range. The TSC2046
operates with a reference in the range of 1V to +VCC. There
are several critical items concerning the reference input
and its wide voltage range. As the reference voltage is
reduced, the analog voltage weight of each digital output
code is also reduced. This is often referred to as the LSB
(least significant bit) size and is equal to the reference
voltage divided by 4096 in 12-bit mode. Any offset or gain
error inherent in the ADC appears to increase, in terms of
LSB size, as the reference voltage is reduced. For
example, if the offset of a given converter is 2LSBs with a
2.5V reference, it is typically 5LSBs with a 1V reference.
In each case, the actual offset of the device is the same,
1.22mV. With a lower reference voltage, more care must
be taken to provide a clean layout including adequate
bypassing, a clean (low-noise, low-ripple) power supply, a
low-noise reference (if an external reference is used), and
a low-noise input signal.
The voltage into the VREF input directly drives the
capacitor digital-to-analog converter (CDAC) portion of the
TSC2046. Therefore, the input current is very low (typically
< 13µA).
+IN
+REF
Converter
−IN
−REF
Y−
GND
Figure 4. Simplified Diagram of Single-Ended
Reference (SER/DFR high, Y switches enabled,
X+ is analog input)
This situation can be remedied as shown in Figure 5. By
setting the SER/DFR bit low, the +REF and –REF inputs
are connected directly to Y+ and Y–, respectively, which
makes the analog-to-digital conversion ratiometric. The
result of the conversion is always a percentage of the
external resistance, regardless of how it changes in
relation to the on-resistance of the internal switches. Note
that there is an important consideration regarding power
dissipation when using the ratiometric mode of operation
(see the Power Dissipation section for more details).
11
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
+VCC
Y+
X+
+IN
+REF
TSC2046 data rate. Once the required number of
conversions have been made, the processor commands
the TSC2046 to go into its power-down state on the last
measurement. This process is required for X-Position,
Y-Position, and Z-Position measurements. Option 3 is to
operate in the 15 Clock-per-Conversion mode, which
overlaps the analog-to-digital conversions and maintains
the touch screen drivers on until commanded to stop by the
processor (see Figure 13).
Converter
−IN
−REF
TEMPERATURE MEASUREMENT
Y−
GND
Figure 5. Simplified Diagram of Differential
Reference (SER/DFR low, Y switches enabled,
X+ is analog input)
As a final note about the differential reference mode, it
must be used with +VCC as the source of the +REF voltage
and cannot be used with VREF. It is possible to use a
high-precision reference on VREF and single-ended
reference mode for measurements which do not need to
be ratiometric. In some cases, it is possible to power the
converter directly from a precision reference. Most
references can provide enough power for the TSC2046,
but might not be able to supply enough current for the
external load (such as a resistive touch screen).
TOUCH SCREEN SETTLING
In some applications, external capacitors may be required
across the touch screen for filtering noise picked up by the
touch screen (e.g., noise generated by the LCD panel or
backlight circuitry). These capacitors provide a low-pass
filter to reduce the noise, but cause a settling time
requirement when the panel is touched that typically
shows up as a gain error. There are several methods for
minimizing or eliminating this issue. The problem is that
the input and/or reference has not settled to the final
steady-state value prior to the ADC sampling the input(s)
and providing the digital output. Additionally, the reference
voltage may still be changing during the measurement
cycle. Option 1 is to stop or slow down the TSC2046 DCLK
for the required touch screen settling time. This allows the
input and reference to have stable values for the Acquire
period (3 clock cycles of the TSC2046; see Figure 9). This
works for both the single-ended and the differential modes.
Option 2 is to operate the TSC2046 in the differential mode
only for the touch screen measurements and command
the TSC2046 to remain on (touch screen drivers ON) and
not go into power-down (PD0 = 1). Several conversions
are made depending on the settling time required and the
12
In some applications, such as battery recharging, a
measurement of ambient temperature is required. The
temperature measurement technique used in the
TSC2046 relies on the characteristics of a semiconductor
junction operating at a fixed current level. The forward
diode voltage (VBE) has a well-defined characteristic
versus temperature. The ambient temperature can be
predicted in applications by knowing the +25°C value of
the VBE voltage and then monitoring the delta of that
voltage as the temperature changes. The TSC2046 offers
two modes of operation. The first mode requires
calibration at a known temperature, but only requires a
single reading to predict the ambient temperature. A diode
is used (turned on) during this measurement cycle. The
voltage across the diode is connected through the MUX for
digitizing the forward bias voltage by the ADC with an
address of A2 = 0, A1 = 0, and A0 = 0 (see Table 1 and
Figure 6 for details). This voltage is typically 600mV at
+25°C with a 20µA current through the diode. The absolute
value of this diode voltage can vary a few millivolts.
However, the TC of this voltage is very consistent at
–2.1mV/°C. During the final test of the end product, the
diode voltage would be stored at a known room
temperature, in memory, for calibration purposes by the
user. The result is an equivalent temperature
measurement resolution of 0.3°C/LSB (in 12-bit mode).
+VCC
TE MP 0
TEM P1
MUX
ADC
Figure 6. Functional Block Diagram of
Temperature Measurement
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The second mode does not require a test temperature
calibration, but uses a two-measurement method to eliminate
the need for absolute temperature calibration and for
achieving 2°C accuracy. This mode requires a second
conversion with an address of A2 = 1, A1 = 1, and A0 = 1,
with a 91 times larger current. The voltage difference
between the first and second conversion using 91 times the
bias current is represented by Equation (1):
DV + kT
q @ In(N)
(1)
where:
N is the current ratio = 91.
BATTERY MEASUREMENT
An added feature of the TSC2046 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 0V to 6V, while maintaining the voltage
to the TSC2046 at 2.7V, 3.3V, etc. The input voltage (VBAT)
is divided down by 4 so that a 5.5V battery voltage is
represented as 1.375V to the ADC. This simplifies the
multiplexer and control logic. In order to minimize the power
consumption, the divider is only on during the sampling
period when A2 = 0, A1 = 1, and A0 = 0 (see Table 1 for the
relationship between the control bits and configuration of the
TSC2046).
k = Boltzmann’s constant = 1.3807 × 10−23 J/K
(joules/kelvins).
q = the electron charge = 1.6022 × 10–19 C (coulombs).
T = the temperature in kelvins (K).
This method can provide improved absolute temperature
measurement, but at a lower resolution of 1.6°C/LSB. The
resulting equation that solves for T is:
T+
q @ DV
k @ In(N)
DC/DC
Converter
Battery
0.5V +
to
5.5V
+VCC
(2)
0.125V to 1.375V
VBAT
where:
∆V = VBE(TEMP1) − VBE(TEMP0) (in mV)
∴ T = 2.573 ⋅ ∆V (in K)
2.7V
ADC
7.5kΩ
2.5kΩ
or T = 2.573 ⋅ ∆V – 273 (in °C)
NOTE: The bias current for each diode temperature
measurement is only on for 3 clock cycles (during the
acquisition mode) and, therefore, does not add any
noticeable increase in power, especially if the temperature
measurement only occurs occasionally.
Figure 7. Battery Measurement Functional Block
Diagram
13
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PRESSURE MEASUREMENT
DIGITAL INTERFACE
Measuring touch pressure can also be done with the
TSC2046. To determine pen or finger touch, the pressure
of the touch needs to be determined. Generally, it is not
necessary to have very high performance for this test;
therefore, the 8-bit resolution mode is recommended
(however, calculations will be shown here in the 12-bit
resolution mode). There are several different ways of
performing this measurement. The TSC2046 supports two
methods. The first method requires knowing the X-plate
resistance, measurement of the X-Position, and two
additional cross panel measurements (Z1 and Z2) of the
touch screen, as shown in Figure 8. Using Equation (3)
calculates the touch resistance:
See Figure 9 for the typical operation of the TSC2046
digital interface. This diagram assumes that the source of
the digital signals is a microcontroller or digital signal
processor with a basic serial interface. Each
communication between the processor and the converter,
such as SPI, SSI, or Microwiret synchronous serial
interface, consists of eight clock cycles. One complete
conversion can be accomplished with three serial
communications for a total of 24 clock cycles on the DCLK
input.
ǒ
Ǔ
Z
R TOUCH + RX−Plate @ X−Position 2 *1
4096
Z1
The first eight clock cycles are used to provide the control
byte via the DIN pin. When the converter has enough
information about the following conversion to set the input
multiplexer and reference inputs appropriately, the
converter enters the acquisition (sample) mode and, if
needed, the touch panel drivers are turned on. After three
more clock cycles, the control byte is complete and the
converter enters the conversion mode. At this point, the
input sample-and-hold goes into the hold mode and the
touch panel drivers turn off (in single-ended mode). The
next 12 clock cycles accomplish the actual analogto-digital conversion. If the conversion is ratiometric
(SER/DFR = 0), the drivers are on during the conversion
and a 13th clock cycle is needed for the last bit of the
conversion result. Three more clock cycles are needed to
complete the last byte (DOUT will be low), which are
ignored by the converter.
(3)
The second method requires knowing both the X-plate
and Y-plate resistance, measurement of X-Position and
Y-Position, and Z1. Using Equation (4) also calculates
the touch resistance:
R TOUCH +
ǒ
Ǔ
RX−Plate @ X−Position 4096
*1
4096
Z1
ǒ
Ǔ
*R Y−Plate 1* Y−Position
4096
(4)
Microwire is a registered trademark of National Semiconductor.
Measure
X−Position
Measure
Z1−Position
Y+
X+
X+
Y+
Y+
X+
Touch
Touch
Touch
X−Position
Z1−Position
X−
Y−
X−
Z2−Position
X−
Y−
Figure 8. Pressure Measurement Block Diagrams
14
Y−
Measure
Z2−Position
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Control Byte
mode, the converter reference voltage is always the
difference between the VREF and GND pins (see Table 1
and Table 2, and Figure 2 through Figure 5, for further
information).
The control byte (on DIN), as shown in Table 3, provides the
start conversion, addressing, ADC resolution, configuration,
and power-down of the TSC2046. Figure 9, Table 3 and
Table 4 give detailed information regarding the order and
description of these control bits within the control byte.
Initiate START—The first bit, the S bit, must always be
high and initiates the start of the control byte. The
TSC2046 ignores inputs on the DIN pin until the start bit is
detected.
BIT 7
(MSB)
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
(LSB)
S
A2
A1
A0
MODE
SER/DFR
PD1
PD0
Table 3. Order of the Control Bits in the Control
Byte
Addressing—The next three bits (A2, A1, and A0) select
the active input channel(s) of the input multiplexer (see
Table 1, Table 2, and Figure 2), touch screen drivers, and
the reference inputs.
MODE—The mode bit sets the resolution of the ADC. With
this bit low, the next conversion has 12 bits of resolution,
whereas with this bit high, the next conversion has eight
bits of resolution.
SER/DFR—The SER/DFR bit controls the reference
mode, either single-ended (high) or differential (low). The
differential mode is also referred to as the ratiometric
conversion mode and is preferred for X-Position,
Y-Position, and Pressure-Touch measurements for
optimum performance. The reference is derived from the
voltage at the switch drivers, which is almost the same as
the voltage to the touch screen. In this case, a reference
voltage is not needed as the reference voltage to the ADC
is the voltage across the touch screen. In the single-ended
BIT
NAME
DESCRIPTION
7
S
Start bit. Control byte starts with first high bit on DIN.
A new control byte can start every 15th clock cycle
in 12-bit conversion mode or every 11th clock cycle
in 8-bit conversion mode (see Figure 13).
6-4
A2-A0
Channel Select bits. Along with the SER/DFR bit,
these bits control the setting of the multiplexer input,
touch driver switches, and reference inputs (see
Table 1 and Figure 13).
3
MODE
12-Bit/8-Bit Conversion Select bit. This bit controls
the number of bits for the next conversion: 12-bits
(low) or 8-bits (high).
2
SER/DFR
Single-Ended/Differential Reference Select bit. Along
with bits A2-A0, this bit controls the setting of the
multiplexer input, touch driver switches, and
reference inputs (see Table 1 and Table 2).
1-0
PD1-PD0
Power-Down Mode Select bits. Refer to Table 5 for
details.
Table 4. Descriptions of the Control Bits within
the Control Byte
CS
t ACQ
DCLK
DIN
1
S
8
A2
A1
A0
MO D E
SER/
DFR
1
8
1
8
PD1 PD0
(START)
Idle
Conversion
Acquire
Idle
BUSY
DOUT
11
10
9
8
7
6
5
4
3
(MSB)
2
1
0
Zero Filled...
(LSB)
(1)
Drivers 1 and 2
(SER/DFR High)
Off
Drivers 1 and 2(1, 2)
(SER/DFR Low)
Off
On
Off
On
Off
NOTES: (1) For Y−Position, Driver 1 is on X+ is selected, and Driver 2 is off. For X−Position, Driver 1 is off, Y+ is selected, and Driver 2 is on. Y− will turn on
when power−down mode is entered and PD0 = 0.
(2) Drivers will remain on if PD0 = 1 (no power down) until selected input channel, reference mode, or p ower−down mode is changed, or CS is high.
Figure 9. Conversion Timing, 24 Clocks-per-Conversion, 8-Bit Bus Interface.
No DCLK delay required with dedicated serial port
15
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If X-Position, Y-Position, and Pressure-Touch are
measured in the single-ended mode, an external reference
voltage is needed. The TSC2046 must also be powered
from the external reference. Caution should be observed
when using the single-ended mode such that the input
voltage to the ADC does not exceed the internal reference
voltage, especially if the supply voltage is greater than
2.7V.
NOTE: The differential mode can only be used for
X-Position,
Y-Position,
and
Pressure-Touch
measurements. All other measurements require the
single-ended mode.
PD0 and PD1—Table 5 describes the power-down and
the internal reference voltage configurations. The internal
reference voltage can be turned on or off independently of
the ADC. This can allow extra time for the internal
reference voltage to settle to the final value prior to making
a conversion. Make sure to also allow this extra wake-up
time if the internal reference is powered down. The ADC
requires no wake-up time and can be instantaneously
used. Also note that the status of the internal reference
power-down is latched into the part (internally) with BUSY
going high. In order to turn the reference off, an additional
write to the TSC2046 is required after the channel has
been converted.
PD1
PD0
PENIRQ
DESCRIPTION
0
0
Enabled
Power-Down Between Conversions. When
each conversion is finished, the converter
enters a low-power mode. At the start of the
next conversion, the device instantly powers up
to full power. There is no need for additional
delays to ensure full operation, and the very first
conversion is valid. The Y− switch is on when in
power-down.
0
1
Disabled
Reference is off and ADC is on.
1
0
Enabled
Reference is on and ADC is off.
1
1
Disabled
Device is always powered. Reference is on and
ADC is on.
Table 5. Power-Down and Internal Reference
Selection
PENIRQ OUTPUT
The pen-interrupt output function is shown in Figure 10.
While in power-down mode with PD0 = 0, the Y-driver is on
and connects the Y-plane of the touch screen to GND. The
PENIRQ output is connected to the X+ input through two
transmission gates. When the screen is touched, the X+
input is pulled to ground through the touch screen.
In most of the TSC2046 models, the internal pullup resistor
value is nominally 50kΩ, but this may vary between 36kΩ
and 67kΩ given process and temperature variations. In order
to assure a logic low of 0.35 S (+VCC) is presented to the
PENIRQ circuitry, the total resistance between the X+ and
Y− terminals must be less than 21kΩ.
16
IOVDD
+V CC
Level
Shifter
50kΩ
or
90kΩ
+VCC
TEMP0
Y+
High except
when TEMP0,
TEMP1 activated.
X+
PENIRQ
TEMP1
TEMP
DIODE
Y−
On
Y+ or X+ drivers on,
or TEMP0, TEMP1
measurements activated.
Figure 10. PENIRQ Functional Block Diagram
The −90 version of the TSC2046 uses a nominal 90kΩ
pullup resistor, which allows the total resistance between
the X+ and Y− terminals to be as high as 30kΩ. Note that
the higher pullup resistance will cause a slower response
time of the PENIRQ to a screen touch, so user software
should take this into account.
The PENIRQ output goes low due to the current path through
the touch screen to ground, which initiates an interrupt to the
processor. During the measurement cycle for X-, Y-, and
Z-Position, the X+ input is disconnected from the PENIRQ
internal pull-up resistor. This is done to eliminate any leakage
current from the internal pull-up resistor through the touch
screen, thus causing no errors.
Furthermore, the PENIRQ output is disabled and low during
the measurement cycle for X-, Y-, and Z-Position. The
PENIRQ output is disabled and high during the
measurement cycle for battery monitor, auxiliary input, and
chip temperature. If the last control byte written to the
TSC2046 contains PD0 = 1, the pen-interrupt output function
is disabled and is not able to detect when the screen is
touched. In order to re-enable the pen-interrupt output
function under these circumstances, a control byte needs to
be written to the TSC2046 with PD0 = 0. If the last control
byte written to the TSC2046 contains PD0 = 0, the
pen-interrupt output function is enabled at the end of the
conversion. The end of the conversion occurs on the falling
edge of DCLK after bit 1 of the converted data is clocked out
of the TSC2046.
It is recommended that the processor mask the interrupt
PENIRQ is associated with whenever the processor sends
a control byte to the TSC2046. This prevents false triggering
of interrupts when the PENIRQ output is disabled in the
cases discussed in this section.
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16 Clocks-per-Conversion
Digital Timing
The control bits for conversion n + 1 can be overlapped
with conversion n to allow for a conversion every 16 clock
cycles, as shown in Figure 11. This figure also shows
possible serial communication occurring with other serial
peripherals between each byte transfer from the processor
to the converter. This is possible, provided that each
conversion completes within 1.6ms of starting. Otherwise,
the signal that is captured on the input sample-and-hold
may droop enough to affect the conversion result. Note
that the TSC2046 is fully powered while other serial
communications are taking place during a conversion.
Figure 9, Figure 12, and Table 6 provide detailed timing for
the digital interface of the TSC2046.
15 Clocks-per-Conversion
Figure 13 provides the fastest way to clock the TSC2046.
This method does not work with the serial interface of most
microcontrollers and digital signal processors, as they are
generally not capable of providing 15 clock cycles per
serial transfer. However, this method can be used with
field-programmable gate arrays (FPGAs) or applicationspecific integrated circuits (ASICs). Note that this
effectively increases the maximum conversion rate of the
converter beyond the values given in the specification
tables, which assume 16 clock cycles per conversion.
CS
DCLK
1
DIN
8
8
1
S
1
8
1
S
Control Bits
Control Bits
BUSY
DOUT
11 10 9
8
7
6
5
4
3
2
1
11 10 9
0
Figure 11. Conversion Timing, 16 Clocks-per-Conversion, 8-Bit Bus Interface.
No DCLK delay required with dedicated serial port
CS
tCSS
tCL
t CH
tBD
tBD
tDO
tCSH
DCLK
t DS
tDH
PD0
DIN
tBDV
tBTR
BUSY
tDV
DOUT
tTR
11
10
Figure 12. Detailed Timing Diagram
17
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SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
+VCC S 2.7V, +VCC S IOVDD S 1.5V, CLOAD = 50pF
MIN
TYP
MAX
SYMBOL
DESCRIPTION
tACQ
tDS
Acquisition Time
1.5
µs
DIN Valid Prior to DCLK Rising
100
ns
DIN Hold After DCLK High
50
tDH
tDO
tDV
tTR
UNITS
ns
DCLK Falling to DOUT Valid
200
ns
CS Falling to DOUT Enabled
200
ns
CS Rising to DOUT Disabled
200
ns
tCSS
tCSH
CS Falling to First DCLK Rising
100
ns
CS Rising to DCLK Ignored
10
ns
tCH
tCL
DCLK High
200
ns
DCLK Low
200
tBD
DCLK Falling to BUSY Rising/Falling
200
ns
tBDV
tBTR
CS Falling to BUSY Enabled
200
ns
CS Rising to BUSY Disabled
200
ns
ns
Table 6. Timing Specifications, TA = −405C to +855C
Power−Down
CS
DCLK
15
1
DIN
S A2 A1 A0
MOD E
SER/
DFR
1
15
S A2 A1 A0
PD1 PD0
M ODE
SER/
DFR
1
0
1
S A2 A1 A0
PD1 PD0
BUSY
DOUT
11 10
9
8
7
6
5
4
3
2
11 10
9
8
7
Figure 13. Maximum Conversion Rate, 15 Clocks-per-Conversion
Data Format
FS = Full− Scale Voltage = VREF(1)
1LSB = VREF(1)/4096
The TSC2046 output data is in Straight Binary format, as
shown in Figure 14. This figure shows the ideal output
code for the given input voltage and does not include the
effects of offset, gain, or noise.
The TSC2046 provides an 8-bit conversion mode that can
be used when faster throughput is needed and the digital
result is not as critical. By switching to the 8-bit mode, a
conversion is complete four clock cycles earlier. Not only
does this shorten each conversion by four bits (25% faster
throughput), but each conversion can actually occur at a
faster clock rate. This is because the internal settling time
of the TSC2046 is not as critical—settling to better than 8
bits is all that is needed. The clock rate can be as much as
50% faster. The faster clock rate and fewer clock cycles
combine to provide a 2x increase in conversion rate.
11...110
Output Code
8-Bit Conversion
1LSB
11...111
11...101
00...010
00...001
00...000
0V
Input Voltage(2) (V)
FS − 1LSB
NOTES: (1) Reference voltage at converter: +REF − (−REF); see Figure 2.
(2) Input voltage at converter, after multiplexer: +IN − (−IN); see
Figure 2.
Figure 14. Ideal Input Voltages and Output Codes
18
"#$%&
www.ti.com
SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
POWER DISSIPATION
There are two major power modes for the TSC2046:
full-power (PD0 = 1) and auto power-down (PD0 = 0).
When
operating
at
full
speed
and
16
clocks-per-conversion (see Figure 11), the TSC2046
spends most of the time acquiring or converting. There is
little time for auto power-down, assuming that this mode is
active. Therefore, the difference between full-power mode
and auto power-down is negligible. If the conversion rate
is decreased by slowing the frequency of the DCLK input,
the two modes remain approximately equal. However, if
the DCLK frequency is kept at the maximum rate during a
conversion but conversions are done less often, the
difference between the two modes is dramatic.
Figure 15 shows the difference between reducing the
DCLK frequency (scaling DCLK to match the conversion
rate) or maintaining DCLK at the highest frequency and
reducing the number of conversions per second. In the
latter case, the converter spends an increasing
percentage of time in power-down mode (assuming the
auto power-down mode is active).
Another important consideration for power dissipation is
the reference mode of the converter. In the single-ended
reference mode, the touch panel drivers are ON only when
the analog input voltage is being acquired (see Figure 9
and Table 1). The external device (e.g., a resistive touch
screen), therefore, is only powered during the acquisition
period. In the differential reference mode, the external
device must be powered throughout the acquisition and
conversion periods (see Figure 9). If the conversion rate is
high, this could substantially increase power dissipation.
CS also puts the TSC2046 into power-down mode. When
CS goes high, the TSC2046 immediately goes into
power-down mode and does not complete the current
conversion. The internal reference, however, does not turn
off with CS going high. To turn the reference off, an
additional write is required before CS goes high (PD1 = 0).
When the TSC2046 first powers up, the device draws
about 20µA of current until a control byte is written to it with
PD0 = 0 to put it into power-down mode. This can be
avoided if the TSC2046 is powered up with CS = 0 and
DCLK = IOVDD.
1000
Supply Current (µA)
fCLK = 16 ⋅ fSAMPLE
100
f CLK = 2MHz
Supply Current from
+V C C and IO VDD
10
TA = 25¡C
+VCC = 2.7V
IOVDD = 1.8V
1
1k
10k
100k
1M
fSAMPLE (Hz)
Figure 15. Supply Current versus Directly Scaling
the Frequency of DCLK with Sample Rate or
Maintaining DCLK at the Maximum Possible
Frequency
19
"#$%&
www.ti.com
SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
LAYOUT
The following layout suggestions provide the most
optimum performance from the TSC2046. Many portable
applications, however, have conflicting requirements
concerning power, cost, size, and weight. In general, most
portable devices have fairly clean power and grounds
because most of the internal components are very low
power. This situation means less bypassing for the
converter power and less concern regarding grounding.
Still, each situation is unique and the following
suggestions should be reviewed carefully.
For optimum performance, care should be taken with the
physical layout of the TSC2046 circuitry. The basic SAR
architecture is sensitive to glitches or sudden changes on
the power supply, reference, ground connections, and
digital inputs that occur just prior to latching the output of
the analog comparator. Therefore, during any single
conversion for an n-bit SAR converter, there are n
‘windows’ in which large external transient voltages can
easily affect the conversion result. Such glitches can
originate from switching power supplies, nearby digital
logic, and high-power devices. The degree of error in the
digital output depends on the reference voltage, layout,
and the exact timing of the external event. The error can
change if the external event changes in time with respect
to the DCLK input.
With this in mind, power to the TSC2046 should be clean
and well bypassed. A 0.1µF ceramic bypass capacitor
should be placed as close to the device as possible. A 1µF
to 10µF capacitor may also be needed if the impedance of
the connection between +VCC or IOVDD and the power
supplies is high. Low-leakage capacitors should be used
to minimize power dissipation through the bypass
capacitors when the TSC2046 is in power-down mode.
A bypass capacitor is generally not needed on the VREF
pin because the internal reference is buffered by an
internal op amp. If an external reference voltage originates
from an op amp, make sure that it can drive any bypass
capacitor that is used without oscillation.
20
The TSC2046 architecture offers no inherent rejection of
noise or voltage variation in regards to using an external
reference input. This is of particular concern when the
reference input is tied to the power supply. Any noise and
ripple from the supply appears directly in the digital results.
Whereas high-frequency noise can be filtered out, voltage
variation due to line frequency (50Hz or 60Hz) can be
difficult to remove.
The GND pin must be connected to a clean ground point.
In many cases, this is the analog ground. Avoid
connections which are too near the grounding point of a
microcontroller or digital signal processor. If needed, run
a ground trace directly from the converter to the
power-supply entry or battery connection point. The ideal
layout includes an analog ground plane dedicated to the
converter and associated analog circuitry.
In the specific case of use with a resistive touch screen,
care should be taken with the connection between the
converter and the touch screen. Although resistive touch
screens have fairly low resistance, the interconnection
should be as short and robust as possible. Longer
connections are a source of error, much like the
on-resistance of the internal switches. Likewise, loose
connections can be a source of error when the contact
resistance changes with flexing or vibrations.
As indicated previously, noise can be a major source of
error in touch screen applications (e.g., applications that
require a backlit LCD panel). This EMI noise can be
coupled through the LCD panel to the touch screen and
cause flickering of the converted data. Several things can
be done to reduce this error, such as using a touch screen
with a bottom-side metal layer connected to ground to
shunt the majority of noise to ground. Additionally, filtering
capacitors from Y+, Y–, X+, and X− pins to ground can also
help. Caution should be observed under these
circumstances for settling time of the touch screen,
especially operating in the single-ended mode and at high
data rates.
"#$%&
www.ti.com
SBAS265G − OCTOBER 2002 − REVISED JANUARY 2008
Revision History
DATE
REV
1/08
G
8/07
F
PAGE
SECTION
3, 4
Electrical Chartacteristics
13
Temperature Measurement
5
Pin Configuration
DESCRIPTION
Fixed typos in conditions header and in Note (6).
Fixed typos in Equations (1) and (2).
Added note to QFN package.
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
21
PACKAGE OPTION ADDENDUM
www.ti.com
24-Aug-2014
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
TSC2046EIPWG4
ACTIVE
TSSOP
PW
16
90
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
TSC
2046EI
TSC2046EIPWRG4
ACTIVE
TSSOP
PW
16
2000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
TSC
2046EI
TSC2046IPW
ACTIVE
TSSOP
PW
16
90
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC
2046I
TSC2046IPWG4
ACTIVE
TSSOP
PW
16
90
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC
2046I
TSC2046IPWR
ACTIVE
TSSOP
PW
16
2500
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC
2046I
TSC2046IPWRG4
ACTIVE
TSSOP
PW
16
2500
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC
2046I
TSC2046IRGVR
ACTIVE
VQFN
RGV
16
2500
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
TSC
2046
TSC2046IRGVRG4
ACTIVE
VQFN
RGV
16
2500
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
TSC
2046
TSC2046IRGVT
ACTIVE
VQFN
RGV
16
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
TSC
2046
TSC2046IZQCR
ACTIVE
BGA
MICROSTAR
JUNIOR
ZQC
48
2500
Pb-Free
(RoHS)
SNAGCU
Level-3-260C-168 HR
-40 to 85
BC2046
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
24-Aug-2014
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
1-Nov-2016
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
TSC2046IPWR
TSSOP
PW
16
2500
330.0
12.4
6.9
5.6
1.6
8.0
12.0
Q1
TSC2046IRGVR
VQFN
RGV
16
2500
330.0
12.4
4.25
4.25
1.15
8.0
12.0
Q2
TSC2046IRGVT
VQFN
RGV
16
250
180.0
12.4
4.25
4.25
1.15
8.0
12.0
Q2
ZQC
48
2500
330.0
12.4
4.3
4.3
1.5
8.0
12.0
Q1
TSC2046IZQCR
BGA MI
CROSTA
R JUNI
OR
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
1-Nov-2016
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
TSC2046IPWR
TSC2046IRGVR
TSSOP
PW
16
2500
367.0
367.0
38.0
VQFN
RGV
16
2500
367.0
367.0
35.0
TSC2046IRGVT
VQFN
RGV
16
250
210.0
185.0
35.0
TSC2046IZQCR
BGA MICROSTAR
JUNIOR
ZQC
48
2500
336.6
336.6
28.6
Pack Materials-Page 2
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