TSC2003
TSC
2003
TSC2
003
SBAS162G – NOVEMBER 2000 – REVISED JUNE 2007
I2C TOUCH SCREEN CONTROLLER
DESCRIPTION
FEATURES
● 2.5V TO 5.25V OPERATION
● INTERNAL 2.5V REFERENCE
● DIRECT BATTERY MEASUREMENT
(0.5V TO 6V)
● ON-CHIP TEMPERATURE MEASUREMENT
● TOUCH-PRESSURE MEASUREMENT
● I2C INTERFACE SUPPORTS:
Standard, Fast, and High-Speed Modes
● AUTO POWER DOWN
● TSSOP-16 AND VFBGA-48 PACKAGES
The TSC2003 is a 4-wire resistive touch screen controller. It
also features direct measurement of two batteries, two auxiliary analog inputs, temperature measurement, and touchpressure measurement.
The TSC2003 has an on-chip 2.5V reference that can be
utilized for the auxiliary inputs, battery monitors, and temperature-measurement modes. The reference can also be
powered down when not used to conserve power. The
internal reference will operate down to 2.7V supply voltage
while monitoring the battery voltage from 0.5V to 6V.
The TSC2003 is available in the small TSSOP-16 and
VFBGA-48 packages and is specified over the –40°C to
+85°C temperature range.
APPLICATIONS
●
●
●
●
●
●
PERSONAL DIGITAL ASSISTANTS
PORTABLE INSTRUMENTS
POINT-OF-SALES TERMINALS
PAGERS
TOUCH SCREEN MONITORS
CELLULAR PHONES
VDD
PENIRQ
TEMP0
X+
X–
TEMP1
SCL
VDD
SAR
SDA
Y+
Y–
I2C
Interface
and
Control
Logic
Comparator
MUX
CDAC
A0
IN1
IN2
VBAT1
Internal
Clock
Channel Select
A1
VBAT2
Internal
+2.5VREF
VREF
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.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright © 2000-2007, Texas Instruments Incorporated
www.ti.com
PACKAGE/ORDERING INFORMATION(1)
MAXIMUM
RELATIVE ACCURACY
(LSB)
MAXIMUM
GAIN ERROR
(LSB)
PACKAGE-LEAD
PACKAGE
DESIGNATOR
TSC2003
TSC2003
TSC2003
TSC2003
±2
±2
±2
±2
±4
±4
±4
±4
TSSOP-16
TSSOP-16
TSSOP-16
TSSOP-16
TSC2003
TSC2003
±2
±2
±4
±4
VFBGA-48
VFBGA-48
PRODUCT
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER
PW
PW
PW
PW
–40°C
–40°C
–40°C
–40°C
TSC2003I
TSC2003I
TSC2003I
TSC2003I
TSC2003IPW
TSC2003IPWT
TSC2003IPWR
TSC2003IPWRG4
ZQC
ZQC
–40°C to +85°C
–40°C to +85°C
BC2003
BC2003
TSC2003IZQCT
TSC2003IZQCR
to
to
to
to
+85°C
+85°C
+85°C
+85°C
NOTE: (1) For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet, or refer to our web
site at www.ti.com.
ELECTROSTATIC
DISCHARGE SENSITIVITY
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.
ABSOLUTE MAXIMUM RATINGS(1)
+VDD to GND ........................................................................ –0.3V to +6V
Digital Input Voltage to GND ................................. –0.3V to +VDD + 0.3V
Analog Input Voltage to GND. All Pins Except 7, 8 ...... –0.3V to +VDD + 0.3V
Analog Input Voltage Pins 7, 8 to GND ........................... –0.3V to +6.0V
Operating Temperature Range ........................................ –40°C to +85°C
Storage Temperature Range ......................................... –65°C to +150°C
Power Dissipation .......................................................... (TJ Max – TA)/θJA
TSSOP Package
Junction Temperature (TJ Max) .............................................. +150°C
θJA Thermal Impedance ................................................... +115.2°C/W
Lead Temperature, Soldering
Vapor Phase (60s) ............................................................ +215°C
Infrared (15s) ..................................................................... +220°C
VFBGA Package
PIN CONFIGURATION
Junction Temperature (TJ Max) .............................................. +125°C
Top View
θJA Thermal Impedance ........................................................ +50°C/W
TSSOP
Lead Temperature, Soldering
Vapor Phase (60s) ............................................................ +215°C
+VDD
1
16
IN1
X+
2
15
IN2
Y+
3
14
A0
X–
4
13
A1
Y–
5
12
SCL
GND
6
11
SDA
VBAT1
7
10
PENIRQ
VBAT2
8
9
VREF
TSC2003
Infrared (15s) ..................................................................... +220°C
NOTE: (1) Stresses above those listed under Absolute Maximum Ratings may
cause permanent damage to the device. Exposure to absolute maximum
conditions for extended periods may affect device reliability.
PIN DESCRIPTIONS
TSSOP VFBGA
Top View
PIN #
PIN #
NAME
DESCRIPTION
1
C1, D1
+VDD
Power Supply
2
E1
X+
X+ Position Input
3
F1
Y+
Y+ Position Input
4
G1
X–
X– Position Input
5
G2
Y–
Y– Position Input
6
G3, G4
GND
Ground
7
G5
VBAT1
Battery Monitor Input
8
G6
VBAT2
Battery Monitor Input
9
B7
VREF
Voltage Reference Input/Output
10
A7
PENIRQ
11
A6
SDA
12
A4
SCL
13
A3
A1
I2C Bus Address Input A1
14
A2
A0
I2C Bus Address Input A0
15
A1
IN2
Auxiliary A/D Converter Input
16
B1
IN1
Auxiliary A/D Converter Input
VFBGA
A0
1
A1
2
SCL
3
SDA PENIRQ
4
5
A
6
7
NC
IN2
B
NC
C
NC
NC
NC
NC
NC
NC
NC
NC
VREF
IN1
NC
+VDD
D
NC
NC
NC
NC
NC
NC
E
NC
NC
NC
NC
NC
NC
F
NC
NC
NC
NC
NC
NC
+VDD
X+
Y+
G
NC
X−
Y−
GND
GND
VBAT1
VBAT2
Pen Interrupt. Open Drain Output (Requires
30kΩ to 100kΩ pull-up resistor externally).
Serial Data
Serial Clock
NC = No Connection
TSC2003
2
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SBAS162G
ELECTRICAL CHARACTERISTICS
At TA = –40°C to +85°C, +VDD = +2.7V, VREF = 2.5V external voltage, I2C bus frequency = 3.4MHz, 12-bit mode and digital inputs = GND or +VDD, unless
otherwise noted.
TSC2003I
PARAMETER
CONDITIONS
ANALOG INPUT
Full-Scale Input Span
Absolute Input Range
Capacitance
Leakage Current
SYSTEM PERFORMANCE
Resolution
No Missing Codes
Integral Linearity Error
Offset Error
Gain Error
Noise
Power-Supply Rejection Ratio
SAMPLING DYNAMICS
Throughput Rate
Channel-to-Channel Isolation
SWITCH DRIVERS
On-Resistance
Y+, X+
Y–, X–
Drive Current(2)
REFERENCE OUTPUT
Internal Reference Voltage
Internal Reference Drift
Output Impedance
Quiescent Current
REFERENCE INPUT
Range
Resistance
BATTERY MONITOR
Input Voltage Range
Input Impedance
Accuracy
TEMPERATURE MEASUREMENT
Temperature Range
Resolution
Accuracy
DIGITAL INPUT/OUTPUT
Logic Family
Logic Levels, Except PENIRQ
VIH
VIL
VOH
VOL
PENIRQ VOL
Data Format
Input Capacitance
TYP
0
–0.2
MAX
UNITS
VREF
+VDD +0.2
V
V
pF
µA
25
0.1
12
Standard and Fast Mode
High-Speed Mode
Standard and Fast Mode
High-Speed Mode
70
70
Bits
Bits
Bits
LSB(1)
LSB
LSB
LSB
µVrms
dB
50
100
ksps
dB
5.5
7.3
Ω
Ω
mA
11
10
±2
±4
±6
±4
Including Internal VREF
VIN = 2.5Vp-p at 50kHz
Duration 100ms
50
2.45
Internal Reference ON
Internal Reference OFF
PD1 = 1, PD0 = 0, SDA, SCL High
2.50
25
300
1
750
2.0
PD1 = PD0 = 0
2.55
V
ppm/°C
Ω
GΩ
µA
VDD
V
GΩ
6.0
V
kΩ
GΩ
%
%
1
0.5
Sampling Battery
Battery Monitor OFF
External VREF = 2.5V
Internal Reference
10
1
–2
–3
+2
+3
–40
Differential Method(3)
TEMP0(4)
Differential Method(3)
TEMP0(4)
+85
°C
°C
°C
°C
°C
+VDD + 0.3
+VDD • 0.3
0.4
0.4
V
V
V
V
V
10
pF
1.6
0.3
±2
±3
CMOS
| IIH | ≤ +5µA
| IIL | ≤ +5µA
IOH = –250µA
IOL = 250µA
30kΩ Pull-Up
+VDD • 0.7
–0.3
+VDD • 0.8
Straight
Binary
SDA, SCL Lines
TSC2003
SBAS162G
MIN
3
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ELECTRICAL CHARACTERISTICS (Cont.)
At TA = –40°C to +85°C, +VDD = +2.7V, VREF = 2.5V external voltage, I2C bus frequency = 3.4MHz, 12-bit mode and digital inputs = GND or +VDD, unless
otherwise noted.
TSC2003I
PARAMETER
CONDITIONS
POWER-SUPPLY REQUIREMENTS
+VDD
MIN
Specified Performance
Operating Range
Internal Reference OFF,
PD1 = PD0 = 0
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode: SCL = 100kHz
Internal Reference ON, PD0 = 0
Internal Reference OFF,
PD1 = PD0 = 0
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode: SCL = 100kHz
PD1 = PD0 = 0, SDA = SCL = +VDD
+VDD = +2.7V
Quiescent Current
Power-Down Current when Part is
Not Addressed
Power Dissipation
TYP
2.7
2.5
254
95
63
1005
MAX
3.6
5.25
V
V
650
µA
µA
µA
µA
3
1.8
µA
µA
µA
µA
mW
+85
°C
90
21
4
TEMPERATURE RANGE
Specified Performance
–40
UNITS
NOTES: (1) LSB means Least Significant Bit. With VREF equal to +2.5V, one LSB is 610µV. (2) Ensured by design, but not tested. Exceeding 50mA source current may
result in device degradation. (3) Difference between TEMP0 and TEMP1 measurement. No calibration necessary. (4) Temperature drift is –2.1mV/°C.
TIMING DIAGRAM
trDA
tfDA
SDA
tBUF
tLOW
trCL
tfCL
tHD; STA
tSP
SCL
tHD; STA
tHD; DAT
tSU; DAT
tSU; STA
tHIGH
STOP START
trCL1
tSU; STO
REPEATED
START
TSC2003
4
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SBAS162G
TIMING CHARACTERISTICS
At TA = –40°C to +85°C, +VDD = +2.7V, unless otherwise noted. All values referred to VIHMIN and VILMAX levels.
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
SCL Clock Frequency
fSCL
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
0
0
0
0
100
400
3.4
1.7
kHz
kHz
MHz
MHz
Bus Free Time Between a STOP and
Start Condition
tBUF
Standard Mode
Fast Mode
4.7
1.3
µs
µs
Standard Mode
Fast Mode
High-Speed Mode
4.0
600
160
µs
ns
ns
Hold Time (Repeated) START
Condition
tHD;
STA
LOW Period of the SCL Clock
tLOW
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
4.7
1.3
160
320
µs
µs
ns
ns
HIGH Period of the SCL Clock
tHIGH
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
4.0
600
60
120
µs
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode
4.7
600
160
µs
ns
ns
Standard Mode
Fast Mode
High-Speed Mode
250
100
10
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
0
0
0
0
3.45
0.9
70
150
µs
µs
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
20 + 0.1Cb
10
20
1000
300
40
80
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
20 + 0.1Cb
10
20
1000
300
80
160
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
20 + 0.1Cb
10
20
300
300
40
80
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
20 + 0.1Cb
10
20
1000
300
80
160
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, Cb = 100pF max
High-Speed Mode, Cb = 400pF max
20 + 0.1Cb
10
20
300
300
80
160
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode
4.0
600
160
Setup Time for a Repeated START
Condition
tSU;
STA
Data Setup Time
tSU;
DAT
Data Hold Time
tHD;
DAT
Rise Time of SCL Signal
trCL
Rise Time of SCL Signal After a
Repeated START Condition and
After an Acknowledge Bit
trCL1
Fall Time of SCL Signal
tfCL
Rise Time of SDA Signal
Fall Time of SDA Signal
Setup Time for STOP Condition
trDA
tfDA
tSU;
STO
µs
ns
ns
Capacitive Load for SDA or SCL
Line
Cb
Standard Mode
Fast Mode
High-Speed Mode, SCL = 1.7MHz
High-Speed Mode, SCL = 3.4MHz
Pulse Width of Spike Suppressed
tSP
Fast Mode
High-Speed Mode
0
0
Noise Margin at the HIGH Level for
Each Connected Device (Including
Hysteresis)
VnH
Standard Mode
Fast Mode
High-Speed Mode
0.2VDD
V
Standard Mode
Fast Mode
High-Speed Mode
0.1VDD
V
Noise Margin at LOW Level for Each
Connected Device (Including
Hysteresis)
VnL
TSC2003
SBAS162G
400
400
400
100
pF
pF
pF
pF
50
10
ns
ns
5
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POWER-ON SEQUENCE TIMING
During TSC2003 power-up, the I2C bus should be idle. In
other words, the SDA and SCL lines must be high before the
TSC supply (+VDD) ramps up greater than 0.9V. If the TSC
uses the same supply as the the I2C bus pull-up resistors
(VI2C), then a 1µF capacitor placed very close to the TSC
supply pin will cause the TSC supply to ramp up more slowly
(refer to the Power-On Sequence timing diagram). If the TSC
supply (+VDD) is different than the supply to the I2C bus pullup resistors (VI2C), then VI2C should be turned on before the
TSC supply (+VDD) is powered up.
POWER-ON SEQUENCE TIMING DIAGRAM
t1 ≥ 0
TSC Supply
+VDD
100% VDD
~ 0.9V
0V
SCL High
100% VI2C
SCL
I2C Bus Activity
~ 0.9V
0V
100% VI2C
SDA
~ 0.9V
0V
SDA Low
I2C Bus Activity
TSC2003
6
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SBAS162G
TYPICAL CHARACTERISTICS: +2.7V
At TA = +25°C, +VDD = +2.7V, VREF = External +2.5V, I2C bus frequency = 3.4MHz, PD1 = PD0 =0, unless otherwise noted.
SUPPLY CURRENT vs VDD
SUPPLY CURRENT vs TEMPERATURE
300
High-Speed Mode = 3.4MHz
Supply Current (µA)
Supply Current (µA)
250
200
150
Fast Mode = 400kHz
100
50
Standard Mode = 100kHz
0
–40
–20
0
20
40
60
80
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
High-Speed Mode = 3.4MHz
Fast Mode = 400kHz
Standard Mode = 100kHz
2.5
100
3.0
3.5
4.0
SUPPLY CURRENT vs I2C BUS FREQUENCY
300
900
High-Speed Mode
200
150
100
700
600
500
Fast
Mode = 400kHz
400
300
Standard
Mode = 100kHz
200
100
Fast/Standard Mode
100
1000
0
10000
2.5
3.0
3.5
I2C Bus Frequency (kHz)
4.0
4.5
5.0
5.5
VDD (V)
SUPPLY CURRENT (Part Not Addressed)
vs TEMPERATURE
CHANGE IN GAIN vs TEMPERATURE
100
4.0
90
High-Speed Mode = 3.4MHz
70
60
50
Fast Mode = 400kHz
40
30
20
Standard Mode = 100kHz
10
Gain Delta from +25˚C (LSB)
3.0
80
Supply Current (µA)
5.5
High-Speed Mode = 3.4MHz
800
Supply Current (µA)
Supply Current (µA)
250
10
5.0
SUPPLY CURRENT (Part Not Addressed) vs VDD
1000
50
4.5
VDD (V)
Temperature (°C)
0
2.0
1.0
0.0
–1.0
–2.0
–3.0
–4.0
–40
–20
0
20
40
60
80
100
–40
Temperature (°C)
0
20
40
60
80
100
Temperature (°C)
TSC2003
SBAS162G
–20
7
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TYPICAL CHARACTERISTICS: +2.7V (Cont.)
At TA = +25°C, +VDD = +2.7V, VREF = External +2.5V, I2C bus frequency = 3.4MHz, PD1 = PD0 =0, unless otherwise noted.
EXTERNAL REFERENCE CURRENT
vs TEMPERATURE
6.0
10
5.0
9
External Reference Current (µA)
Offset Delta from +25°C (LSB)
CHANGE IN OFFSET vs TEMPERATURE
4.0
3.0
2.0
1.0
0.0
–1.0
–2.0
–3.0
–4.0
–5.0
8
High-Speed Mode = 3.4MHz
7
6
5
4
Fast Mode = 400kHz
3
Standard Mode = 100kHz
2
1
0
–6.0
–40
–20
0
20
40
60
80
–40
100
–20
0
Temperature (°C)
9
9
8
8
X–
7
7
6
6
Y–
RON (Ω)
RON (Ω)
SWITCH-ON RESISTANCE vs VDD
(X+, Y+: +VDD to Pin; X–, Y–: Pin to GND)
5
4
X+
3
Y+
40
60
80
100
SWITCH-ON RESISTANCE vs TEMPERATURE
(X+, Y+: +VDD to Pin; X–, Y–: Pin to GND)
X–
Y–
5
Y+
4
X+
3
2
2
1
1
0
0
2.5
3
3.5
4
4.5
5
–40
5.5
–20
INTERNAL VREF vs TEMPERATURE
2.54
2.54
2.53
2.53
2.52
2.52
Internal VREF (V)
2.55
2.50
2.49
2.48
40
20
60
80
100
INTERNAL VREF vs VDD
2.55
2.51
0
Temperature (°C)
VDD (V)
2.51
2.50
2.49
2.48
2.47
2.47
2.46
2.46
2.45
2.45
–40
–35
–30
–25
–20
–15
–10
–05
0
05
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
Internal VREF (V)
20
Temperature (°C)
2.5
3
3.5
4
4.5
5
5.5
VDD (V)
Temperature (°C)
TSC2003
8
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SBAS162G
TYPICAL CHARACTERISTICS: +2.7V (Cont.)
At TA = +25°C, +VDD = +2.7V, VREF = External +2.5V, I2C bus frequency = 3.4MHz, PD1 = PD0 =0, unless otherwise noted.
TEMP DIODE VOLTAGE vs TEMPERATURE
TEMP0 DIODE VOLTAGE vs VDD (25°C)
850
614
TEMP1
TEMP0 Diode Voltage (mV)
Temp Diode Voltage (mV)
800
750
700
650
600
TEMP0
550
500
450
613
612
611
–40
–35
–30
–25
–20
–15
–10
–05
0
05
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
610
2.5
3.0
3.5
Temperature (°C)
4.0
4.5
5.0
5.5
VDD (V)
TEMP1 DIODE VOLTAGE vs VDD (25°C)
738
TEMP1 Diode Voltage (mV)
736
734
732
730
728
726
724
722
720
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
TSC2003
SBAS162G
9
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THEORY OF OPERATION
a differential input to the converter, and a differential reference architecture, it is possible to negate the switch’s onresistance error (should this be a source of error for the
particular measurement).
The TSC2003 is a classic Successive Approximation
Register (SAR) Analog-to-Digital (A/D) converter. The architecture is based on capacitive redistribution which inherently
includes a sample-and-hold function. The converter is fabricated on a 0.6µ CMOS process.
ANALOG INPUT
See Figure 2 for a block diagram of the input multiplexer on
the TSC2003, the differential input of the A/D converter, and
the converter's differential reference.
The basic operation of the TSC2003 is shown in Figure 1.
The device features an internal 2.5V reference and an
internal 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 2V and
+VDD. The value of the reference voltage directly sets the
input range of the converter.
When the converter enters the Hold mode, the voltage
difference between the +IN and –IN inputs (see Figure 2) is
captured on the internal capacitor array. The input current on
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 has been fully charged, there is no further input
current. The amount of charge transfer from the analog
source to the converter is a function of conversion rate.
The analog input (X, Y, and Z parallel coordinates, auxiliary
inputs, battery voltage, and chip temperature) to the converter is provided via a multiplexer. 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 an external device. By maintaining
Voltage
Regulator
+2.7V to +5V
1.2kΩ
1µF
+
to
10µF
(Optional)
50kΩ
TSC2003
0.1µF
Touch
Screen
1
+VDD
IN1 16
Auxiliary Input
2
X+
IN2 15
Auxiliary Input
3
Y+
A0 14
4
X–
A1 13
5
Y–
SCL 12
Serial Clock
6
GND
SDA 11
Serial Data
7
VBAT1
PENIRQ 10
8
VBAT2
VREF
Pen Interrupt
9
0.1µF
Main
Battery
1.2kΩ
+
1µF
to
10µF
(Optional)
Secondary
Battery
FIGURE 1. Basic Operation of the TSC2003.
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SBAS162G
+VDD
PENIRQ
TEMP1
VREF
TEMP0
C2-C0
(Shown 101B)
C3
(Shown HIGH)
X+
X–
Ref ON/OFF
Y+
+IN
Y–
+REF
Converter
–IN
2.5V
Reference
–REF
7.5kΩ
VBAT1
7.5kΩ
VBAT2
2.5kΩ
2.5kΩ
Battery
On
Battery
On
IN1
IN2
GND
FIGURE 2. Simplified Diagram of the Analog Input.
INTERNAL REFERENCE
Reference
Power Down
The TSC2003 has an internal 2.5V voltage reference that
can be turned ON or OFF with the power-down control bits,
PD0 and PD1 (see Table II and Figure 3). The internal
reference is powered down when power is first applied to the
device.
The internal reference voltage is only used in the
single-ended reference mode for battery monitoring, temperature measurement, and for measuring the auxiliary input. Optimal touch screen performance is achieved when
using a ratiometric conversion; thus, all touch screen measurements are done automatically in the differential mode.
Band
Gap
VREF
Buffer
To
CDAC
Optional
FIGURE 3. Simplified Diagram of the Internal Reference.
TSC2003
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REFERENCE INPUT
REFERENCE MODE
The voltage difference between +REF and –REF (see
Figure 2) sets the analog input range. The TSC2003 will
operate with a reference in the range of 2V to +VDD. 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
(256 if in 8-bit mode). Any Offset or Gain error inherent in the
A/D converter will appear 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 will
typically be 2.5LSBs with a 2V 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, lowripple) power supply, a low-noise reference (if an external
reference is used), and a low-noise input signal.
There is 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
TSC2003 (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 A/D converter,
turning on the Y+ and Y– drivers, and digitizing the voltage
on X+, as shown in Figure 4. For this measurement, the
resistance in the X+ lead does not affect the conversion; it
does, however, 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 would not be 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.
The voltage into the VREF input is not buffered, and directly
drives the Capacitor Digital-to-Analog Converter (CDAC)
portion of the TSC2003. Therefore, the input current is very
low, typically < 6µA.
VREF
+VDD
This situation is remedied, as shown in Figure 5, by using the
differential mode: the +REF and –REF inputs are connected
directly to Y+ and Y–, respectively. This makes the A/D
converter ratiometric. The result of the conversion is always a
percentage of the external reference, regardless of how it
changes in relation to the on-resistance of the internal switches.
+VDD
Y+
X+
+IN
+REF
Y+
Converter
–IN
–REF
Y–
X+
+IN
+REF
Converter
–IN
–REF
GND
Y–
FIGURE 4. Simplified Diagram of Single-Ended Reference.
GND
FIGURE 5. Simplified Diagram of Differential Reference (Y
Switches Enabled, X+ is Analog Input).
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Differential reference mode always uses the supply voltage,
through the drivers, as the reference voltage for the A/D
converter. VREF cannot be used as the reference voltage in
differential mode.
It is possible to use a high-precision reference on VREF in
single-ended reference mode for measurements which do
not need to be ratiometric (i.e., battery voltage, temperature
measurement, etc.). In some cases, it could be possible to
power the converter directly from a precision reference. Most
references can provide enough power for the TSC2003, but
they might not be able to supply enough current for the
external load, such as a resistive touch screen.
the Temperature Coefficient (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.
X+
MUX
A/D
Converter
TOUCH SCREEN SETTLING
In some applications, external capacitors may be required
across the touch screen for filtering noise picked up by the
touch screen (i.e., noise generated by the LCD panel or
backlight circuitry). These capacitors will provide a low-pass
filter to reduce the noise, but they will also cause a settling
time requirement when the panel is touched. The settling
time will typically show up as a gain error. The problem is that
the input and/or reference has not settled to its final steadystate value prior to the A/D converter sampling the input(s),
and providing the digital output. Additionally, the reference
voltage may still be changing during the measurement cycle.
To resolve these settling time problems, the TSC2003 can be
commanded to turn on the drivers only without performing a
conversion (see Table I). Time can then be allowed before
the command is issued to perform a conversion. Generally,
the time it takes to communicate the conversion command
over the I2C bus is adequate for the touch screen to settle.
TEMPERATURE MEASUREMENT
In some applications, such as battery recharging, a measurement of ambient temperature is required. The temperature
measurement technique used in the TSC2003 relies on the
characteristics of a semiconductor junction operating at a
fixed current level to provide a measurement of the temperature of the TSC2003 chip. The forward diode voltage (VBE)
has a well-defined characteristic versus temperature. The
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 TSC2003
offers two modes of temperature measurement.
The first mode requires calibrations at a known temperature,
but only requires a single reading to predict the ambient
temperature. A diode is used during this measurement cycle.
The voltage across the diode is connected through the MUX
for digitizing the diode forward bias voltage by the A/D
converter with an address of C3 = 0, C2 = 0, C1 = 0, and
C0 = 0 (see Table I and Figure 6 for details). This voltage is
typically 600mV at +25°C, with a 20µA current through it. The
absolute value of this diode voltage can vary a few millivolts;
Temperature Select
TEMP0
FIGURE 6. Functional Block Diagram of Temperature Measurement Mode.
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/LSB accuracy. This mode requires a second conversion with an address of C3 = 0, C2 = 1, C1 = 0, and C0 = 0,
with an 91 times larger current. The voltage difference
between the first and second conversion using 91 times the
bias current will be represented by kT/q • 1n (N), where N is
the current ratio = 91, k = Boltzmann's constant (1.38054 •
10–23 electrons volts/degrees Kelvin), q = the electron charge
(1.602189 • 10–19 C), and T = the temperature in degrees
Kelvin. This mode can provide improved absolute temperature measurement over the first mode, but at the cost of less
resolution (1.6°C/LSB). The equation to solve for °K is:
°K =
q • ∆V
k • 1n(N)
(1)
where:
∆V = V(I91) – V(I1) (in mV)
∴ oK = 2.573∆VoK/mV
o
C = 2.573 • ∆V(mV) – 273o K
NOTE: The bias current for each diode temperature measurement is only turned ON during the acquisition mode,
and, therefore, does not add any noticeable increase in
power, especially if the temperature measurement only occurs occasionally.
TSC2003
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BATTERY MEASUREMENT
An added feature of the TSC2003 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 0.5V to 6V, while the voltage regulator maintains the voltage to the TSC2003 at 2.7V, 3.3V, etc. The input
voltage (VBAT1 or VBAT2) is divided down by 4 so that a 6.0V
battery voltage is represented as 1.5V to the A/D converter.
The simplifies the multiplexer and control logic. In order to
minimize the power consumption, the divider is only ON
during the sample period which occurs after control bits C3
= 0, C2 = 0, C1 = 0, and C0 = 1 (VBAT1) or C3 = 0, C2 = 1,
C1 = 0, and C0 = 1 (VBAT2) are received. See Tables I and
II for the relationship between the control bits and configuration of the TSC2003.
The second method requires knowing both the X-Plate and
Y-Plate resistance, measurement of X-Position and Y-Position, and Z1. Equation 3 calculates the touch resistance using
the second method:
R TOUCH =
R X −Plate • X − Position 4096
– 1
4096
Z
1
Y − Position
–R Y −Plate • 1–
4096
(3)
Measure X-Position
X+
Y+
Touch
2.7V
DC/DC
Converter
Battery
0.5V
to
6.0V
X-Position
+
Y–
X–
VDD
Measure Z1-Position
Y+
X+
0.125V to 1.5V
VBAT
A/D
Converter
Touch
7.5kΩ
Z1-Position
2.5kΩ
X–
Y+
X+
FIGURE 7. Battery Measurement Functional Block Diagram.
Y–
Touch
PRESSURE MEASUREMENT
Measuring touch pressure can also be done with the TSC2003.
To determine pen or finger touch, the pressure of the “touch”
needs to be determined. Generally, it is not necessary to
have high accuracy for this test, therefore, the 8-bit resolution
mode is recommended. However, calculations will be shown
with the 12-bit resolution mode. There are several different
ways of performing this measurement—the TSC2003 supports two methods.
The first method requires knowing the X-Plate resistance,
measurement of the X-Position, and two additional
cross-panel measurements (Z2 and Z1) of the touch screen,
as shown in Figure 8. Using Equation 2 will calculate the
touch resistance:
RTOUCH = RX −Plate •
X − Position
4096
Z2
– 1
Z1
(2)
Z2-Position
X–
Y–
Measure Z2-Position
FIGURE 8. Pressure Measurement Block Diagrams.
DIGITAL INTERFACE
The TSC2003 supports the I2C serial bus and data transmission protocol in all three defined modes: standard, fast, and
high-speed. A device that sends data onto the bus is defined
as a transmitter, and a device receiving data as a receiver.
The device that controls the message is called a master. The
devices that are controlled by the master are slaves. The bus
must be controlled by a master device which generates the
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SBAS162G
serial clock (SCL), controls the bus access, and generates
the START and STOP conditions. The TSC2003 operates as
a slave on the I2C bus. Connections to the bus are made via
the open-drain I/O lines SDA and SDL.
stable LOW during the HIGH period of the acknowledge clock
pulse. Of course, setup and hold times must be taken into account.
A master must signal an end of data to the slave by not generating
an acknowledge bit on the last byte that has been clocked out of
the slave. In this case, the slave must leave the data line HIGH to
enable the master to generate the STOP condition.
The following bus protocol has been defined, as shown in
Figure 9:
Figure 9 details how data transfer is accomplished on the I2C
bus. Depending upon the state of the R/W bit, two types of
data transfer are possible:
• Data transfer may be initiated only when the bus is not busy.
• During data transfer, the data line must remain stable
whenever the clock line is HIGH. Changes in the data line
while the clock line is HIGH will be interpreted as control
signals.
• Data transfer from a master transmitter to a slave
receiver. The first byte transmitted by the master is the
slave address. Next follows a number of data bytes. The
slave returns an acknowledge bit after the slave address
and each received byte.
Accordingly, the following bus conditions have been defined:
Bus Not Busy: Both data and clock lines remain HIGH.
Start Data Transfer: A change in the state of the data line,
from HIGH to LOW, while the clock is HIGH defines a START
condition.
• Data transfer from a slave transmitter to a master
receiver. The first byte (the slave address) is transmitted
by the master. The slave then returns an acknowledge bit.
Next, a number of data bytes are transmitted by the slave
to the master. The master returns an acknowledge bit
after all received bytes other than the last one. At the end
of the last received byte, a ‘not acknowledge’ is returned.
Stop Data Transfer: A change in the state of the data line,
from LOW to HIGH, while the clock line is HIGH defines a
STOP condition.
Data Valid: The state of the data line represents valid data
when, after a START condition, the data line is stable for the
duration of the HIGH period of the clock signal. There is one
clock pulse per bit of data.
The master device generates all of the serial clock pulses
and the START and STOP conditions. A transfer is ended
with a STOP condition or a repeated START condition. Since
a repeated START condition is also the beginning of the next
serial transfer, the bus will not be released.
Each data transfer is initiated with a START condition and
terminated with a STOP condition. The number of data bytes
transferred between START and STOP conditions is not
limited, and is determined by the master device. The information is transferred byte-wise, and each receiver acknowledges with a ninth-bit.
The TSC2003 may operate in the following two modes:
• Slave Receiver Mode: Serial data and clock are received
through SDA and SCL. After each byte is received, an
acknowledge bit is transmitted. START and STOP conditions are recognized as the beginning and end of a serial
transfer. Address recognition is performed by hardware
after reception of the slave address and direction bit.
Within the I2C bus specifications, a standard mode (100kHz
clock rate), a fast mode (400kHz clock rate), and a
high-speed mode (3.4MHz clock rate) are defined. The
TSC2003 works in all three modes.
• Slave Transmitter Mode: The first byte (the slave address) is received and handled as in the slave receiver
mode. However, in this mode the direction bit will indicate
that the transfer direction is reversed. Serial data is
transmitted on SDA by the TSC2003 while the serial clock
is input on SCL. START and STOP conditions are recognized as the beginning and end of a serial transfer.
Acknowledge: Each receiving device, when accessed, is
obliged to generate an acknowledge after the reception of
each byte. The master device must generate an extra clock
pulse, which is associated with this acknowledge bit.
A device that acknowledges must pull down the SDA line during
the acknowledge clock pulse in such a way that the SDA line is
SDA
Slave Address
R/W
Direction
Bit
Acknowledgement
Signal from
Receiver
Acknowledgement
Signal from
Receiver
1
SCL
2
6
7
8
9
ACK
START
Condition
1
2
3-7
8
9
ACK
Repeated If More Bytes Are Transferred
STOP Condition
or Repeated
START Condition
FIGURE 9. I2C Bus Protocol.
TSC2003
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Address Byte
The address byte, as shown in Figure 10, is the first byte
received following the START condition from the master
device. The first five bits (MSBs) of the slave address are
factory preset to 10010. The next two bits of the address byte
are the device select bits: A1 and A0. Input pins (A1-A0) on
the TSC2003 determine these two bits of the device address
for a particular TSC2003. Therefore, a maximum of four
devices with the same preset code can be connected on the
same bus at one time.
It is recommended to set PD0 = 0 in each command byte to get
the lowest power consumption possible. If multiple X-, Y-, and
Z-position measurements will be done one right after another,
such as when averaging, PD0 =1 will leave the touch screen
drivers on at the end of each conversion cycle.
LSB
MSB
0
1
0
1
0
A1
A0
R/W
FIGURE 10. Address Byte.
The A1-A0 Address Inputs can be connected to VDD or digital
ground. The last bit of the address byte (R/W) defines the
operation to be performed. When set to a “1”, a read
operation is selected; when set to a “0”, a write operation is
selected. Following the START condition, the TSC2003
monitors the SDA bus and checks the device type identifier
being transmitted. Upon receiving the 10010 code, the appropriate device select bits, and the R/W bit, the slave device
outputs an acknowledge signal on the SDA line.
The TSC2003’s operating mode is determined by a command byte, which is shown in Figure 11.
LSB
MSB
C2
C1
• M: Mode bit. If M is 0, the TSC2003 is in 12-bit mode. If
M is 1, 8-bit mode is selected.
• X: Don’t care.
PD1
PD0
PENIRQ
DESCRIPTION
0
0
1
1
0
1
0
1
Enabled
Disabled
Enabled
Disabled
Power-Down Between Conversions
Internal reference OFF, ADC(1) ON
Internal reference ON, ADC(1) OFF
Internal reference ON, ADC(1) ON
NOTE: (1) ADC = Analog-to Digital Converter.
TABLE II. Power-Down Bit Functions.
Command Byte
C3
The internal reference voltage can be turned ON or OFF
independently of the A/D converter. This can allow extra time
for the internal reference voltage to settle to its final value prior
to making a conversion. Make sure to allow this extra wakeup time if the internal reference was powered down. Also note
that the status of the internal reference power down is latched
into the part (internally) when a STOP or repeated START
occurs at the end of a command byte (see Figures 12 and 14).
Therefore, in order to turn the internal reference OFF, an
additional write to the TSC2003, with PD1 = 0, is required after
the channel has been converted.
C0
PD1
PD0
M
X
When the TSC2003 powers up, the power-down mode bits
need to be written to ensure that the part is placed into the
desired mode to achieve lowest power. Therefore, immediately after power-up, a command byte should be sent which
sets PD1 = PD0 = 0, so that the device will be in the lowest
power mode, powering down between conversions.
FIGURE 11. Command Byte.
Start A Conversion/Write Cycle
The bits in the device command byte are defined as follows:
A Conversion/Write Cycle begins when the master issues the
address byte containing the slave address of the TSC2003,
with the eighth bit equal to a 0 (R/W = 0), as shown in Figure
10. Once the eighth bit has been received, and the address
matches the A1-A0 address input pin setting, the TSC2003
issues an acknowledge.
• C3-C0: Configuration bits. These bits set the input multiplexer address and functions that the TSC2003 will perform, as shown in Table I.
• PD1-PD0: Power-down bits. These two bits select the
power-down mode that the TSC2003 will be in after the
current command completes, as shown in Table II.
C3
C2
C1
C0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
FUNCTION
Measure TEMP0
Measure VBAT1
Measure IN1
Reserved
Measure TEMP1
Measure VBAT2
Measure IN2
Reserved
Activate X– Drivers
Activate Y– Drivers
Activate Y+, X– Drivers
Reserved
Measure X Position
Measure Y Position
Measure Z1 Position
Measure Z2 Position
INPUT to ADC
TEMP0
VBAT1
IN1
–
TEMP1
VBAT2
IN2
–
–
–
–
–
Y+
X+
X+
Y–
X-DRIVERS
OFF
OFF
OFF
–
OFF
OFF
OFF
–
ON
OFF
X– ON
–
ON
OFF
X– ON
X– ON
Y-DRIVERS
OFF
OFF
OFF
–
OFF
OFF
OFF
–
OFF
ON
Y+ ON
–
OFF
ON
Y+ ON
Y+ ON
REFERENCE MODE
Single-Ended
Single-Ended
Single-Ended
Single-Ended
Single-Ended
Single-Ended
Single-Ended
Single-Ended
Differential
Differential
Differential
Differential
Differential
Differential
Differential
Differential
TABLE I. Possible Input Configurations.
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Read A Conversion/Read Cycle
Once the master receives the acknowledge bit from the
TSC2003, the master writes the command byte to the slave
(see Figure 11). After the command byte is received by the
slave, the slave issues another acknowledge bit. The master
then ends the Write Cycle by issuing a repeated START or
a STOP condition, as shown in Figure 12.
If the master sends additional command bytes after the initial
byte, before sending a STOP or repeated START condition,
the TSC2003 will not acknowledge those bytes.
For best performance, the I2C bus should remain in an idle
state while an A/D conversion is taking place. This prevents
digital clock noise from affecting the bit decisions being made
by the TSC2003. The master should wait for at least 10µs
before attempting to read data from the TSC2003 to realize
this best performance. However, the master does not need
to wait for a completed conversion before beginning a read
from the slave, if full 12-bit performance is not necessary.
The input multiplexer for the A/D converter has its channel
selected when bits C3 through C0 are clocked in. If the
selected channel is an X-,Y-, or Z-position measurement, the
appropriate drivers will turn on once the acquisition period
begins.
Data access begins with the master issuing a START condition
followed by the address byte (see Figure 10) with R/W = 1.
Once the eighth bit has been received, and the address
matches, the slave issues an acknowledge. The first byte of
serial data will follow (D11-D4, MSB first).
When R/W = 0, the input sample acquisition period starts on
the falling edge of SCL once the C0 bit of the command byte
has been latched, and ends when a STOP or repeated
START condition has been issued. A/D conversion starts
immediately after the acquisition period. The multiplexer
inputs to the A/D converter are disabled once the conversion
period starts. However, if an X-, Y-, or Z-position is being
measured, the respective touch screen drivers remain on
during the conversion period. A complete Write Cycle is
shown in Figure 12.
After the first byte has been sent by the slave, it releases the
SDA line for the master to issue an acknowledge. The slave
responds with the second byte of serial data upon receiving
the acknowledge from the master (D3-D0, followed by four 0
bits). The second byte is followed by a NOT acknowledge bit
(ACK = 1) from the master to indicate that the last data byte
has been received. If the master acknowledges the second
data byte, then the data will repeat on subsequent reads with
ACKs between bytes. This is true in both 12-bit and 8-bit
mode. The master will then issue a STOP condition, which
ends the Read Cycle, as shown in Figure 13.
SCL
Address Byte
1
SDA
0
0
1
Command Byte
0
A1
A0
R/W
0
0
C3
C2
C1
C0 PD1 PD0
TSC2003
ACK
M
0
X
TSC2003
ACK
Acquisition
START
Conversion
STOP or
REPEATED START
FIGURE 12. Complete I2C Serial Write Transmission.
SCL
Address Byte
SDA
1
START
0
0
1
0
Date Byte 2
Date Byte 1
A1 A0 R/W
1
0
D11 D10
D9 D8 D7 D6 D5 D4
TSC2003
ACK
0
D3 D2 D1 D0
MASTER
ACK
0
0
0
0
1
MASTER
NACK
STOP or
REPEATED START
FIGURE 13. Complete I2C Serial Read Transmission.
TSC2003
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I2C High-Speed Operation
FS = Full-Scale Voltage = VREF(1)
1LSB = VREF(1)/4096
The TSC2003 can operate with high-speed I2C masters. To
do so, the simple resistor pull-up on SCL must be changed
to the active pull-up, as recommended in the I2C specification.
1LSB
11...111
I2C
bus will be operating in standard or fast mode
The
initially. Following a START condition, the master will send
the code 00001xxx, which the slave will not acknowledge. At
this point, the bus is now operating in high-speed mode. The
bus will remain in high-speed mode until a STOP condition
occurs. Therefore, to maximize throughput only repeated
STARTs should be used to separate transactions.
Output Code
11...110
00...000
Input Voltage(2) (V)
NOTES: (1) Reference voltage at converter: +REF – (–REF). See Figure 2.
(2) Input voltage at converter, after multiplexer: +IN – (–IN). See Figure 2
FIGURE 15. Ideal Input Voltages and Output Codes.
The TSC2003 output data is in Straight Binary format, as
shown in Figure 15. This shows the ideal output code for the
given input voltage, and does not include the effects of
offset, gain, or noise.
LAYOUT
The following layout suggestions should provide optimum
performance from the TSC2003. However, many portable
applications 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 would
mean less bypassing for the converter's power, and less
concern regarding grounding. Still, each situation is unique,
and the following suggestions should be reviewed carefully.
8-Bit Conversion
The TSC2003 provides an 8-bit conversion mode (M = 1)
that can be used when faster throughput is needed, and the
digital result is not as critical (for example, measuring pressure). By switching to the 8-bit mode, a conversion result can
be read by transferring only one data byte.
This shortens each conversion by four bits and reduces data
transfer time which results in fewer clock cycles and provides
lower power consumption.
HS-Mode Enabled
F/S Mode
0
0
Sr
1
0
0
0
1
X
X
X
N
A/D Converter Powers Up and Begins Sampling
A/D Converter Power-Down Mode
1
0
FS – 1LSB
0V
Data Format
0
00...010
00...001
Since the TSC2003 may not have completed a conversion
before a read to the part can be requested, the TSC2003 is
capable of stretching the clock until the converted data is
stored in its internal shift register. Once the data is latched,
the TSC2003 will release the clock line so that the master
can receive the converted data. A complete high-speed
Conversion Cycle is shown in Figure 14.
S
11...101
A1
A0
W
A
C3
C2
C1
C0
PD1
PD0
M
X
A
Programmable
Fixed Address Part
A/D Converter Stops Sampling and Begins Conversion Using Internal Clock
Sr
1
0
0
1
0
A1
A0
R
A
SCLH is stretched LOW until A/D Converter is finished converting data.
A/D Converter Goes Into Power-Down Mode After Finishing Conversion (If PD0 = 0)
D11
D10
D9
D8
D7
D6
D5
D4
A
D3
D2
Exit HS-Mode and Enter F/S Mode
D1
D0
0
0
0
0
N
P
16 Bits + Ack
S = START
Sr = REPEATED START
P = STOP
= Master Controls Bus
= Slave Controls Bus
FIGURE 14. High-Speed I2C Mode Conversion Cycle.
TSC2003
18
www.ti.com
SBAS162G
For optimum performance, care should be taken with the
physical layout of the TSC2003 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 might 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 SCL input.
With this in mind, power to the TSC2003 should be clean and
well bypassed. A 0.1µF ceramic bypass capacitor should be
placed as close to the device as possible. In addition, a 1µF
to 10µF capacitor may also be needed if the impedance of
the connection between +VDD and the power supply is high.
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.
The TSC2003 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
will appear directly in the digital results. While high-frequency
noise can be filtered out, voltage variation due to line frequency (50Hz or 60Hz) can be difficult to remove.
The GND pin should be connected to a clean ground point. In
many cases, this will be 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 point. The
ideal layout will include an analog ground plane dedicated to
the converter and associated analog circuitry.
PENIRQ output is HIGH. While in the power-down mode, with
PD0 = 0, the Y– driver is ON and connected to GND, and the
PENIRQ output is connected to the X+ input. When the panel
is touched, the X+ input is pulled to ground through the touch
screen, and PENIRQ output goes LOW due to the current path
through the panel to GND, initiating an interrupt to the processor.
During the measurement cycle for X-, Y-, and Z-Position, the X+
input will be disconnected from the PENIRQ pull-down transistor to eliminate any leakage current from the pull-up resistor to
flow through the touch screen, thus causing no errors.
In addition to the measurement cycles for X-, Y-, and Zposition, commands which activate the X-drivers, Y-drivers, Y+
and X-drivers without performing a measurement also disconnect the X+ input from the PENIRQ pull-down transistor and
disable the pen-interrupt output function regardless of the value
of the PD0 bit. Under these conditions, the PENIRQ output will
be forced LOW. Furthermore, if the last command byte written
to the TSC2003 contains PD0 = 1, the pen-interrupt output
function will be disabled and will not be able to detect when the
panel is touched. In order to re-enable the pen-interrupt output
function under these circumstances, a command byte needs to
be written to the TSC2003 with PD0 = 0.
Once the bus master sends the address byte with R/W = 0
(see Figure 10) and the TSC2003 sends an acknowledge,
the pen-interrupt function is disabled. If the command which
follows the address byte has PD0 = 0, then the pen-interrupt
function will be enabled at the end of a conversion. This is
approximately 10µs (12-bit mode) or 7µs (8-bit mode) after
the TSC2003 receives a STOP/START condition following
the reception of a command byte (see Figures 12 and 14 for
further details of when the conversion cycle begins).
In both cases listed above, it is recommended that the
master processor mask the interrupt which the PENIRQ is
associated with whenever the host writes to the TSC2003.
This will prevent false triggering of interrupts when the
PENIRQ line is disabled in the cases listed above.
VDD
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. Since resistive touch screens have
fairly low resistance, the interconnection should be as short
and robust as possible. Longer connections will be 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.
30kΩ to 100kΩ
VDD
VDD
10kΩ
TEMP0
TEMP1
Y+
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 utilizing a
touch screen with a bottom-side metal layer connected to ground.
This will couple the majority of noise to ground. Additionally, filtering
capacitors from Y+, Y–, X+, and X– to ground can also help.
HIGH except
when TEMP0,
TEMP1 activated
TEMP
DIODE
X+
Y–
ON
Y+ or X+ drivers on,
or TEMP0, TEMP1
measurements activated
PENIRQ OUTPUT
The pen-interrupt output function is shown in Figure 16. By
connecting a pull-up resistor to VDD (typically 100kΩ), the
FIGURE 16. PENIRQ Functional Block Diagram.
TSC2003
SBAS162G
PENIRQ
19
www.ti.com
Revision History
DATE
REVISION
PAGE
SECTION
6/07
G
6
Timing
DESCRIPTION
Added Power-On Sequence Timing section.
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
TSC2003
20
www.ti.com
SBAS162G
PACKAGE OPTION ADDENDUM
www.ti.com
13-Jul-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
TSC2003IPW
ACTIVE
TSSOP
PW
16
90
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC
2003I
Samples
TSC2003IPWG4
ACTIVE
TSSOP
PW
16
90
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC
2003I
Samples
TSC2003IPWR
ACTIVE
TSSOP
PW
16
2500
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC
2003I
Samples
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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