TSC2000
TSC
200
0
®
SBAS257 – FEBRUARY 2002
PDA ANALOG INTERFACE CIRCUIT
FEATURES
APPLICATIONS
●
●
●
●
●
●
● PERSONAL DIGITAL ASSISTANTS
● CELLULAR PHONES
● MP3 PLAYERS
4-WIRE TOUCH SCREEN INTERFACE
RATIOMETRIC CONVERSION
SINGLE 2.7V TO 3.6V SUPPLY
SERIAL INTERFACE
INTERNAL DETECTION OF SCREEN TOUCH
PROGRAMMABLE 8-, 10-, OR 12-BIT
RESOLUTION
● PROGRAMMABLE SAMPLING RATES
●
●
●
●
●
DESCRIPTION
DIRECT BATTERY MEASUREMENT (0.5V to 6V)
ON-CHIP TEMPERATURE MEASUREMENT
TOUCH-PRESSURE MEASUREMENT
FULL POWER-DOWN CONTROL
TSSOP-20 PACKAGE
The TSC2000 is a complete PDA analog interface circuit. It
contains a complete 12-bit, Analog-to-Digital (A/D) resistive
touch screen converter including drivers, the control to measure touch pressure, and an 8-bit Digital-to-Analog (D/A)
converter output for LCD contrast control. The TSC2000
interfaces to the host controller through a standard SPI™
serial interface. The TSC2000 offers programmable resolution
and sampling rates from 8- to 12-bits and up to 125kHz to
accommodate different screen sizes.
The TSC2000 also offers two battery-measurement inputs,
one of which is capable of reading battery voltages up to 6V
while operating at only 2.7V. It also has an on-chip temperature
sensor capable of reading 0.3°C resolution. The TSC2000 is
available in a TSSOP-20 package.
SPI is a registered trademark of Motorola.
US Patent No. 624639.
MISO
X+
X–
Y+
Y–
SS
Clock
Touch Panel
Drivers
Serial
Interface
and
Control
Logic
Temp Sensor
SCLK
MOSI
A/D Converter
VBAT1
Battery Monitor
VBAT2
Battery Monitor
DAV
MUX
PENIRQ
AUX1
AUX2
Internal 2.5V
Reference
VREF
ARNG
AOUT
D/A Converter
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.
Copyright © 2002, Texas Instruments Incorporated
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.
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ABSOLUTE MAXIMUM RATINGS(1)
ELECTROSTATIC
DISCHARGE SENSITIVITY
VDD to GND ........................................................................... –0.3V to +6V
Digital Input Voltage to GND ................................... –0.3V to VDD + 0.3V
Operating Temperature Range ...................................... –40°C to +105°C
Storage Temperature Range ......................................... –65°C to +150°C
Junction Temperature (TJ Max) .................................................... +150°C
TSSOP Package
Power Dissipation .................................................... (TJ Max – TA)/θJA
θJA Thermal Impedance .......................................................... 93°C/W
Lead Temperature, Soldering
Vapor Phase (60s) ............................................................ +215°C
Infrared (15s) ..................................................................... +220°C
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.
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.
INTEGRAL
LINEARITY
PACKAGE
ERROR (LSB) PACKAGE-LEAD DESIGNATOR(1)
PRODUCT
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER(2)
TRANSPORT
MEDIA, QUANTITY
TSC2000IPW
±2
TSSOP-20
PW
–40°C to +85°C
TSC2000I
TSC2000IPW
Rails, 70
"
"
"
"
"
"
TSC2000IPWR
Tape and Reel, 2000
NOTES: (1) For the most current specifications and package information, refer to our web site at www.ti.com. (2) Models labeled with “R” indicates large quantity
tape and reel.
PIN DESCRIPTION
PIN CONFIGURATION
Top View
TSSOP
+VDD
1
20
AUX1
X+
2
19
AUX2
Y+
3
18
ARNG
X–
4
17
AOUT
Y–
5
16
PENIRQ
TSC2000
2
GND
6
15
MISO
VBAT1
7
14
DAV
VBAT2
8
13
MOSI
VREF
9
12
SS
NC
10
11
SCLK
PIN
NAME
1
2
3
VDD
X+
Y+
4
5
6
7
8
9
10
11
12
X–
Y–
GND
VBAT1
VBAT2
VREF
NC
SCLK
SS
13
MOSI
14
15
DAV
MISO
16
PENIRQ
17
18
19
20
AOUT
ARNG
AUX2
AUX1
DESCRIPTION
Power Supply
X+ Position Input
Y+ Position Input
X– Position Input
Y– Position Input
Ground
Battery Monitor Input 1
Battery Monitor Input 2
Voltage Reference Input/Output
No Connection
Serial Clock Input
Slave Select Input (Active LOW). Data will not be
clocked in to MOSI unless SS is LOW. When SS is
HIGH, MISO is high impedance.
Serial Data Input. Data is clocked in at SCLK falling
edge.
Data Available (Active LOW)
Serial Data Output. Data is clocked out at SCLK
falling edge. High impedance when SS is HIGH.
Pen Interrupt
Analog Output Current from D/A Converter
D/A Converter Analog Output Range Set
Auxiliary A/D Converter Input 2
Auxiliary A/D Converter Input 1
TSC2000
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SBAS257
ELECTRICAL CHARACTERISTICS
At –40°C to +85°C, +VDD = +2.7V, internal VREF = +2.5V, conversion clock = 2MHz, 12-bit mode, unless otherwise noted.
TSC2000IPW
PARAMETER
CONDITIONS
AUXILIARY ANALOG INPUT
Input Voltage Range
Input Capacitance
Input Leakage Current
BATTERY MONITOR INPUT
Input Voltage Range
Input Voltage Range
Input Capacitance
Input Leakage Current
Accuracy
D/A CONVERTER
Output Current Range
Resolution
Integral Linearity
VOLTAGE REFERENCE
Voltage Range
Reference Drift
External Reference Input Range
Current Drain
DIGITAL INPUT/OUTPUT
Internal Clock Frequency
Logic Family
Logic Levels: VIH
VIL
VOH
VOL
POWER-SUPPLY REQUIREMENTS
Power-Supply Voltage, +VDD
Quiescent Current
TYP
0
MAX
UNITS
+VREF
V
pF
µA
6.0
3.0
V
V
pF
µA
%
25
±1
VBAT1
VBAT2
0.5
0.5
25
±1
–3
TEMPERATURE MEASUREMENT
Temperature Range
Temperature Resolution
Accuracy
A/D CONVERTER
Resolution
No Missing Codes
Integral Linearity
Offset Error
Gain Error
Noise
Power-Supply Rejection
MIN
+3
–40
+85
°C
°C
°C
12
±2
±6
±6
Bits
Bits
LSB
LSB
LSB
µVrms
dB
8
µA
Bits
LSB
0.3
±2
Programmable: 8-, 10-, or 12-Bits
12-Bit Resolution
11
Excluding Reference Error
30
80
Set by Resistor from ARNG to GND
650
±2
Internal 2.5V
Internal 1.25V
2.45
1.225
2.5
1.25
20
1.0
External Reference
2.55
1.275
VDD
20
8
CMOS
IIH = +5µA
IIL = +5µA
IOH = 2 TTL Loads
IOL = 2 TTL Loads
0.7VDD
–0.3
0.8VDD
Specified Performance
See Note (1)
See Note (2)
Power Down
2.7
TEMPERATURE RANGE
Specified Performance
MHz
0.3VDD
0.4
1.25
500
–40
V
V
ppm/°C
V
µA
3.6
2.3
V
V
V
V
3
V
mA
µA
µA
+85
°C
NOTES: (1) AUX1 conversion, no averaging, no REF power down, 50µs conversion. (2) AUX1 conversion, no averaging, external reference, 50µs conversion.
TSC2000
SBAS257
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3
TIMING CHARACTERISTICS(1)(2)
At –40°C to +85°C, +VDD = +2.7V, VREF = +2.5V, unless otherwise noted.
TSC2000
PARAMETER
SCLK Period
Enable Lead Time
Enable Lag Time
Sequential Transfer Delay
Data Setup Time
Data Hold Time (inputs)
Data Hold Time (outputs)
Slave Access Time
Slave DOUT Disable Time
DataValid
Rise Time
Fall Time
CONDITIONS
MIN
tsck
tLead
tLag
ttd
tsu
thi
tho
ta
tdis
tv
tr
tf
30
15
15
30
10
10
0
TYP
MAX
UNITS
15
15
10
30
30
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
NOTES: (1) All input signals are specified with tr = tf = 5ns (10% to 90% of VDD) and timed from a voltage level of (VIL + VIH)/2. (2) See timing diagram below.
TIMING DIAGRAM
All specifications typical at –40°C to +85°C, +VDD = +2.7V.
SS
ttd
tLag
tsck
tLead
twsck
tf
tr
twsck
SCLK
tv
tho
MSB OUT
MISO
tdis
BIT 6 ... 1
LSB OUT
BIT 6 ... 1
LSB IN
ta
tsu
MOSI
4
MSB IN
thi
TSC2000
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SBAS257
TYPICAL CHARACTERISTICS
At TA = +25°C, +VDD = +2.7V, conversion clock = 2MHz, 12-bit mode. Internal VREF = +2.5V, unless otherwise noted.
CONVERSION SUPPLY CURRENT vs TEMPERATURE
(AUX1 Conversion, No Averaging,
No REF Power-Down, 20µs Conversion)
POWER-DOWN SUPPLY CURRENT
vs TEMPERATURE
7
2
6
1.95
1.9
IDD (nA)
IDD (mA)
5
1.85
4
3
2
1.8
1
0
1.75
–60
–40
–20
0
20
40
60
80
–60
100
–40
–20
POWER-DOWN SUPPLY CURRENT vs
SUPPLY VOLTAGE
40
60
80
100
INTERNAL OSCILLATOR FREQUENCY vs VDD
Internal Oscillator Frequency (MHz)
0.11
0.1
0.09
0.08
0.07
8.25
8.2
8.15
8.1
8.05
8
7.95
7.9
7.85
7.8
0.06
2.5
2.9
2.7
3.1
3.3
3.5
2.5
3.7
2.7
3.1
2.9
Supply Voltage (V)
3.3
3.5
3.7
VDD (V)
CHANGE IN GAIN ERROR vs TEMPERATURE
CHANGE IN OFFSET ERROR vs TEMPERATURE
0.5
0.5
0.4
0.4
0.3
0.3
Change in Offset (LSB)
Change in Gain Error (LSB)
20
8.3
0.12
Power-Down Current (nA)
0
Temperature (°C)
Temperature (°C)
0.2
0.1
0
–0.1
–0.2
–0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.4
–0.5
–0.5
–60
–40
–20
0
20
40
60
80
–60
100
TSC2000
SBAS257
–40
–20
0
20
40
60
80
100
Temperature (°C)
Temperature (°C)
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5
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, +VDD = +2.7V, conversion clock = 2MHz, 12-bit mode. Internal VREF = +2.5V, unless otherwise noted.
INTERNAL REFERENCE vs VDD
INTERNAL REFERENCE vs TEMPERATURE
2.55
1.275
2.54
1.27
2.54
1.27
2.53
1.265
2.53
1.265
1.26
2.52
VREF (V)
2.51
1.255
2.5
1.25
2.5V Reference
2.49
1.245
1.26
1.25V Reference
2.51
1.25
2.5V Reference
2.49
1.245
2.48
1.24
2.48
1.24
2.47
1.235
2.47
1.235
2.46
1.23
2.46
1.23
1.225
2.45
2.45
–60
–40
–20
0
20
40
60
80
2.7
2.9
3.3
3.5
3.7
VDD (V)
INTERNAL OSCILLATOR FREQUENCY
vs TEMPERATURE
TOUCHSCREEN DRIVER ON-RESISTANCE
vs TEMPERATURE
8
7.5
8.2
7
8
7.8
7.6
6.5
6
5.5
5
7.4
4.5
7.2
4
–60
–40
–20
0
20
40
60
80
100
–60
–40
–20
Temperature (°C)
0
20
40
60
80
100
Temperature (°C)
TEMP1 DIODE VOLTAGE vs TEMPERATURE
TOUCH SCREEN DRIVER ON-RESISTANCE vs VDD
7
800
6.9
750
6.8
700
6.7
Voltage (mV)
On-Resistance (Ω)
3.1
Temperature (°C)
Resistance (Ω)
Internal Oscillator Frequency (MHz)
1.225
2.5
100
8.4
6.6
6.5
6.4
650
600
550
6.3
500
6.2
450
6.1
400
2.5
2.7
2.9
3.1
3.3
3.5
3.7
–60
Supply Voltage (V)
6
1.255
2.5
–40
–20
0
20
40
60
80
100
Temperature (°C)
TSC2000
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SBAS257
VREF (V)
1.25V Reference
2.52
VREF (V)
1.275
VREF (V)
2.55
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, +VDD = +2.7V, conversion clock = 2MHz, 12-bit mode. Internal VREF = +2.5V, unless otherwise noted.
TEMP1 DIODE VOLTAGE vs VDD
TEMP2 DIODE VOLTAGE vs TEMPERATURE
900
612.0
611.8
611.6
TEMP1 Voltage (mV)
Voltage (mV)
800
700
600
611.4
611.2
611.0
610.8
610.6
610.4
610.2
500
–60
610.0
–40
–20
0
20
40
60
80
100
2.5
2.7
3.1
2.9
TEMP2 DIODE VOLTAGE vs VDD
3.5
3.7
DAC OUTPUT CURRENT vs TEMPERATURE
740
1
738
0.95
DAC Output Current (mA)
736
Temp2 Voltage (mV)
3.3
VDD (V)
Temperature (°C)
734
732
730
728
726
724
0.9
0.85
0.8
0.75
0.7
0.65
722
720
0.6
2.5
2.7
2.9
3.1
3.5
3.3
3.7
–60
–40
–20
0
VDD (V)
20
40
60
80
100
Temperature (°C)
DAC MAX CURRENT vs VDD
0.91
DAC Output Current (mA)
0.905
0.9
0.895
0.89
0.885
0.88
0.875
2.5
2.7
2.9
3.1
3.3
3.5
3.7
VDD (V)
TSC2000
SBAS257
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7
OVERVIEW
The TSC2000 is an analog interface circuit for human interface devices. A register-based architecture eases integration
with microprocessor-based systems through a standard SPI
bus. All peripheral functions are controlled through the registers and onboard state machines.
The TSC2000 consists of the following blocks (refer to the
block diagram on the front page):
• Touch Screen Interface
Control of the TSC2000 and its functions is accomplished by
writing to different registers in the TSC2000. A simple command protocol is used to address the 16-bit registers. Registers control the operation of the A/D converter and D/A
converter.
The result of measurements made will be placed in the
TSC2000’s memory map and may be read by the host at any
time. Three signals are available from the TSC2000 to indicate
that data is available for the host to read. The DAV output
indicates that an A/D conversion has completed and that data
is available. The PENIRQ output indicates that a touch has
been detected on the touch screen. A typical application of the
TSC2000 is shown in Figure 1.
• Battery Monitors
• Auxiliary Inputs
• Temperature Monitor
• Current Output D/A Converter
Voltage
Regulator
1µF
+
to
10µF
(Optional)
+2.7V to +3.3V
LCD Contrast
0.1µF
Touch
Screen
1µF
+
to
10µF
(Optional)
Communication to the TSC2000 is via a standard SPI serial
interface. This interface requires that the Slave Select signal be
driven LOW to communicate with the TSC2000. Data is then
shifted into or out of the TSC2000 under control of the host
microprocessor, which also provides the serial data clock.
0.1µF
Main
Battery
TSC2000
1
+VDD
AUX1
20
Auxiliary Input
2
X+
AUX2
19
Auxiliary Input
3
Y+
ARNG
18
4
X–
AOUT
17
5
Y–
PENIRQ
16
Pen Interrupt Request
6
GND
MISO
15
Serial Data Out
7
VBAT1
DAV
14
Data Available
8
VBAT2
MOSI
13
Serial Data In
9
VREF
SS
12
Slave Select
10
NC
SCLK
11
Serial Clock
Secondary
Battery
RRNG
FIGURE 1. Typical Circuit Configuration.
8
TSC2000
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SBAS257
OPERATION—TOUCH SCREEN
A resistive touch screen works by applying a voltage across
a resistor network and measuring the change in resistance at
a given point on the matrix where a screen is touched by an
input stylus, pen, or finger. The change in the resistance ratio
marks the location on the touch screen.
The TSC2000 supports the resistive 4-wire configurations
(see Figure 1). The circuit determines location in two coordinate pair dimensions, although a third dimension can be
added for measuring pressure.
fore, 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 TSC2000 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 seen in Figure 3. Using
Equation 1 will calculate the touch resistance:
RTOUCH = RX-Plate •
X-Position Z2
–1
4096 Z1
THE 4-WIRE TOUCH SCREEN COORDINATE
PAIR MEASUREMENT
(1)
Measure X-Position
X+
A 4-wire touch screen is constructed as shown in Figure 2.
It consists of two transparent resistive layers separated by
insulating spacers.
Y+
Touch
X-Position
Conductive Bar
Transparent
Conductor (ITO)
Top Side
Y–
X–
Transparent
Conductor (ITO)
Bottom Side
Y+
Measure Z1-Position
Y+
X+
X+
Touch
Z1-Position
X–
Silver
Ink
Y–
X–
Y+
X+
Y–
Touch
Insulating
Material
(Glass)
Z2-Position
ITO = Indium Tin Oxide
X–
Y–
Measure Z2-Position
FIGURE 2. 4-Wire Touch Screen Construction.
The 4-wire touch screen panel works by applying a voltage
across the vertical or horizontal resistive network. The A/D
converter converts the voltage measured at the point the
panel is touched. A measurement of the Y-position of the
pointing device is made by connecting the X+ input to a data
converter chip, turning on the Y+ and Y– drivers, and
digitizing the voltage seen at the X+ input. The voltage
measured is determined by the voltage divider developed at
the point of touch. For this measurement, the horizontal
panel resistance in the X+ lead does not affect the conversion due to the high input impedance of the A/D converter.
Voltage is then applied to the other axis, and the A/D
converter converts the voltage representing the X-position on
the screen. This provides the X- and Y-coordinates to the
associated processor.
Measuring touch pressure (Z) can also be done with the
TSC2000. 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, there-
FIGURE 3. Pressure Measurement.
The second method requires knowing both the X-plate and
Y-plate resistance, measurement of X-position and Y-position, and Z1. Using Equation 2 will also calculate the touch
resistance:
(2)
RTOUCH = RX-Plate •
When the touch panel is pressed or touched, and the drivers
to the panel are turned on, the voltage across the touch panel
will often overshoot and then slowly settle (decay) down to a
stable DC value. This is due to mechanical bouncing which
is caused by vibration of the top layer sheet of the touch
panel when the panel is pressed. This settling time must be
accounted for, or else the converted value will be in error.
Therefore, a delay must be introduced between the time the
driver for a particular measurement is turned on, and the time
measurement is made.
TSC2000
SBAS257
X-Position 4096
Y-Position
–1 −R Y-Plate •
4096 Z1
4096
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9
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
back-light circuitry. The value of these capacitors will provide
a low-pass filter to reduce the noise, but will cause an
additional settling time requirement when the panel is touched.
Several solutions to this problem are available in the TSC2000.
A programmable delay time is available which sets the delay
between turning the drivers on and making a conversion.
This is referred to as the Panel Voltage Stabilization time,
and is used in some of the modes available in the TSC2000.
In other modes, the TSC2000 can be commanded to turn on
the drivers only without performing a conversion. Time can
then be allowed before a conversion is started.
+VDD
TEMP1
The TSC2000 touch screen interface can measure position (X
and Y) and pressure (Z). Determination of these coordinates
is possible under three different modes of the A/D converter:
conversion controlled by the TSC2000, initiated by detection of
a touch; conversion controlled by the TSC2000, initiated by the
host responding to the PENIRQ signal; or conversion completely controlled by the host processor.
A/D CONVERTER
The analog inputs of the TSC2000 are shown in Figure 4. The
analog inputs (X, Y, and Z touch panel coordinates, battery
voltage monitors, chip temperature, and auxiliary inputs) are
provided via a multiplexer to the Successive Approximation
Register (SAR) A/D converter. The A/D converter architecture
is based on capacitive redistribution architecture which inherently includes a sample-and-hold function.
VREF
TEMP0
X+
X–
Ref ON/OFF
Y+
+IN
Y–
+REF
Converter
2.5V
Reference
–IN
–REF
7.5kΩ
VBAT1
2.5kΩ
VBAT2
2.5kΩ
2.5kΩ
Battery
On
Battery
On
AUX1
AUX2
GND
FIGURE 4. Simplified Diagram of the Analog Input Section.
10
TSC2000
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SBAS257
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 driving the
touch panel. By maintaining a differential input to the converter and a differential reference input architecture, it is
possible to negate errors caused by the driver switch onresistances.
The A/D converter is controlled by an A/D Converter Control
Register. Several modes of operation are possible, depending upon the bits set in the control register. Channel selection, scan operation, averaging, resolution, and conversion
rate may all be programmed through this register. These
modes are outlined in the sections below for each type of
analog input. The results of conversions made are stored in
the appropriate result register.
Data Format
The TSC2000 output data is in Straight Binary format, as
shown in Figure 5. This figure shows the ideal output code for
the given input voltage and does not include the effects of
offset, gain, or noise.
FS = Full-Scale Voltage = VREF(1)
1LSB = VREF(1)/4096
1LSB
11...111
Output Code
11...110
11...101
ing the conversions at lower resolutions reduces the amount of
time it takes for the A/D converter to complete its conversion
process, which lowers power consumption.
Conversion Clock and Conversion Time
The TSC2000 contains an internal 8MHz clock, which is used
to drive the state machines inside the device that perform the
many functions of the part. This clock is divided down to
provide a clock to run the A/D converter. The division ratio for
this clock is set in the A/D Converter Control Register. The
ability to change the conversion clock rate allows the user to
choose the optimal value for resolution, speed, and power. If
the 8MHz clock is used directly, the A/D converter is limited to
8-bit resolution; using higher resolutions at this speed will not
result in accurate conversions. Using a 4MHz conversion
clock is suitable for 10-bit resolution; 12-bit resolution requires
that the conversion clock run at 1MHz or 2MHz.
Regardless of the conversion clock speed, the internal clock
will run nominally at 8MHz. The conversion time of the
TSC2000 is dependent upon several functions. While the
conversion clock speed plays an important role in the time it
takes for a conversion to complete, a certain number of
internal clock cycles is needed for proper sampling of the
signal. Moreover, additional times, such as the Panel Voltage
Stabilization time, can add significantly to the time it takes to
perform a conversion. Conversion time can vary depending
upon the mode in which the TSC2000 is used. Throughout
this data sheet, internal and conversion clock cycles will be
used to describe the times that many functions take. In
considering the total system design, these times must be
taken into account by the user.
Touch Detect
00...010
The pen interrupt (PENIRQ) output function is detailed in
Figure 6. While in the power-down mode, 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
00...001
00...000
FS – 1LSB
0V
Input Voltage(2) (V)
NOTES: (1) Reference voltage at converter: +REF – (–REF). See Figure 4.
(2) Input voltage at converter, after multiplexer: +IN – (–IN). See Figure 4.
PENIRQ
VDD
VDD
FIGURE 5. Ideal Input Voltages and Output Codes.
TEMP1
TEMP2
50kΩ
Reference
Y+
The TSC2000 has an internal voltage reference that can be
set to 1.25V or 2.5V, through the Reference Control Register.
HIGH Except
when TEMP1,
TEMP2 Activated
TEMP
DIODE
X+
The internal reference voltage is only used in the singleended mode for battery monitoring, temperature measurement, and for utilizing the auxiliary inputs. Optimal touch
screen performance is achieved when using a ratiometric
conversion, thus all touch screen measurements are done
automatically in the differential mode. An external reference
can also be applied to the VREF pin, and the internal reference can be turned off.
Y–
ON
Y+ or X+ Drivers On,
or TEMP1, TEMP2
Measurements Activated.
Variable Resolution
The TSC2000 provides three different resolutions for the A/D
converter: 8-, 10-, or 12-bits. Lower resolutions are often
practical for measurements such as touch pressure. Perform-
FIGURE 6. PENIRQ Functional Block Diagram.
TSC2000
SBAS257
www.ti.com
11
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 cycles for the X- and Y-positions, 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 modes where the TSC2000 needs to detect if the screen
is still touched (for example, when doing a PENIRQ-initiated
X, Y, and Z conversion), the TSC2000 must reset the drivers
so that the 50kΩ resistor is connected again. Due to the high
value of this pull-up resistor, any capacitance on the touch
screen inputs will cause a long delay time, and may prevent
the detection from occurring correctly. To prevent this, the
TSC2000 has a circuit which allows any screen capacitance
to be “precharged”, so that the pull-up resistor doesn’t have
to be the only source for the charging current. The time
allowed for this precharge, as well as the time needed to
sense if the screen is still touched, can be set in the
Configuration Control register.
This illustrates the need to use the minimum capacitor values
possible on the touch screen inputs. These capacitors may
be needed to reduce noise, but too large a value will increase
the needed precharge and sense times, as well as panel
voltage stabilization time.
The idle state of the serial clock for the TSC2000 is LOW,
which corresponds to a clock polarity setting of 0 (typical
microprocessor SPI control bit CPOL = 0). The TSC2000
interface is designed so that with a clock phase bit setting of
1 (typical microprocessor SPI control bit CPHA = 1), the
master begins driving its MOSI pin and the slave begins
driving its MISO pin on the first serial clock edge. The SS pin
should idle HIGH between transmissions. The TSC2000 will
only interpret command words which are transmitted after the
falling edge of SS.
TSC2000 COMMUNICATION PROTOCOL
The TSC2000 is entirely controlled by registers. Reading and
writing these registers is accomplished by the use of a 16-bit
command, which is sent prior to the data for that register. The
command is constructed as shown in Table I.
The command word begins with a R/W bit, which specifies
the direction of data flow on the serial bus. The following four
bits specify the page of memory this command is directed to,
as shown in Table II. The next six bits specify the register
address on that page of memory to which the data is
directed. The last five bits are reserved for future use.
PG3
PG2
PG1
PG0
PAGE ADDRESSED
0
0
0
0
0
0
0
0
1
1
0
0
1
0
Reserved
0
0
1
1
Reserved
0
1
0
0
Reserved
0
1
0
1
Reserved
0
1
1
0
Reserved
0
1
1
1
Reserved
1
0
0
0
Reserved
1
0
0
1
Reserved
1
0
1
0
Reserved
1
0
1
1
Reserved
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
Reserved
DIGITAL INTERFACE
The TSC2000 communicates through a standard SPI bus.
The SPI allows full-duplex, synchronous, serial communication between a host processor (the master) and peripheral
devices (slaves). The SPI master generates the synchronizing clock and initiates transmissions. The SPI slave devices
depend on a master to start and synchronize transmissions.
A transmission begins when initiated by a master SPI. The
byte from the master SPI begins shifting in on the slave
MOSI pin under the control of the master serial clock. As the
byte shifts in on the MOSI pin, a byte shifts out on the MISO
pin to the master shift register.
TABLE II. Page Addressing.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 0
R/W
PG3
PG2
PG1
PG0
ADDR5
ADDR4
ADDR3
ADDR2
ADDR1
ADDR0
X
X
X
X
X
TABLE I. TSC2000 Command Word.
12
TSC2000
www.ti.com
SBAS257
To read all the first page of memory, for example, the host
processor must send the TSC2000 the command 8000H—this
specifies a read operation beginning at Page 0, Address 0. The
processor can then start clocking data out of the TSC2000. The
TSC2000 will automatically increment its address pointer to the
end of the page; if the host processor continues clocking data
out past the end of a page, the TSC2000 will simply send back
the value FFFFH.
PAGE 0: DATA REGISTERS
PAGE 1: CONTROL REGISTERS
ADDR
REGISTER
ADDR
REGISTER
00
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
0F
10
11
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
X
Y
Z1
Z2
Reserved
BAT1
BAT2
AUX1
AUX2
TEMP1
TEMP2
DAC
Reserved
Reserved
Reserved
Reserved
ZERO
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
00
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
0F
10
11
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
ADC
Reserved
DACCTL
REF
RESET
CONFIG
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Likewise, writing to Page 1 of memory would consist of the
processor writing the command 0800H, which would specify a
write operation, with PG0 set to 1, and all the ADDR bits set
to 0. This would result in the address pointer pointing at the
first location in memory on Page 1. See the TSC2000 Memory
Map section for details of register locations. Figure 7 shows an
example of a complete data transaction between the host
processor and the TSC2000.
TSC2000 MEMORY MAP
The TSC2000 has several 16-bit registers which allow control
of the device as well as providing a location for results from the
TSC2000 to be stored until read by the host microprocessor.
These registers are separated into two pages of memory in the
TSC2000: a Data page (Page 0) and a Control page (Page 1).
The memory map is shown in Table III.
TABLE III. TSC2000 Memory Map.
Read Operation
Write Operation
SS
SCLK
MOSI
Command Word
Data
Command Word
MISO
Data
Data
FIGURE 7. Write and Read Operation of TSC2000 Interface.
TSC2000
SBAS257
www.ti.com
13
TSC2000 CONTROL REGISTERS
the TSC2000, bits in control registers may refer to slightly
different functions depending upon if you are reading the
register or writing to it. A summary of all registers and bit
locations is shown in Table IV.
This section will describe each of the registers that were
shown in the memory map of Table III. The registers are
grouped according to the function they control. Note that in
PAGE
ADDR
(HEX)
REGISTER
NAME
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
RESET
VALUE
(HEX)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
00
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
0F
10
11
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
00
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
0F
10
11
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
X
Y
Z1
Z2
Reserved
BAT1
BAT2
AUX1
AUX2
TEMP1
TEMP2
DAC
Reserved
Reserved
Reserved
Reserved
ZERO
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
ADC
Reserved
DACCTL
REF
RESET
CONFIG
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
0
0
0
0
0
0
0
0
0
0
0
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
PSM
0
DPD
X
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
STS
1
0
X
0
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
AD3
0
0
X
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
AD2
0
0
X
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R11
R11
R11
R11
0
R11
R11
R11
R11
R11
R11
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
AD1
0
0
X
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R10
R10
R10
R10
0
R10
R10
R10
R10
R10
R10
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
AD0
0
0
X
0
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R9
R9
R9
R9
0
R9
R9
R9
R9
R9
R9
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
RS1
0
0
X
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R8
R8
R8
R8
0
R8
R8
R8
R8
R8
R8
X
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
RS0
0
0
X
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R7
R7
R7
R7
0
R7
R7
R7
R7
R7
R7
D7
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
AV1
0
0
X
X
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R6
R6
R6
R6
0
R6
R6
R6
R6
R6
R6
D6
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
AV0
0
0
X
X
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R5
R5
R5
R5
0
R5
R5
R5
R5
R5
R5
D5
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
CL1
0
0
X
X
PR2
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R4
R4
R4
R4
0
R4
R4
R4
R4
R4
R4
D4
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
CL0
0
0
INT
X
PR1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R3
R3
R3
R3
0
R3
R3
R3
R3
R3
R3
D3
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
PV2
0
0
DL1
X
PR0
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R2
R2
R2
R2
0
R2
R2
R2
R2
R2
R2
D2
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
PV1
0
0
DL0
X
SN2
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R1
R1
R1
R1
0
R1
R1
R1
R1
R1
R1
D1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
PV0
0
0
PND
X
SN1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
R0
R0
R0
R0
0
R0
R0
R0
R0
R0
R0
D0
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
x
0
0
RFV
X
SN0
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
007F
FFFF
FFFF
FFFF
FFFF
0000
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
4000
4000
8000
0002
FFFF
FFC0
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
0000
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
FFFF
NOTE: X = Don’t Care.
TABLE IV. Register Summary for TSC2000.
14
TSC2000
www.ti.com
SBAS257
TSC2000 A/D CONVERTER CONTROL REGISTER
(PAGE 1, ADDRESS 00H)
The A/D converter in the TSC2000 is shared between all the
different functions. A control register determines which input
is selected, as well as other options. The result of the
conversion is placed in one of the result registers in Page 0
of memory, depending upon the function selected.
lifted or the process is stopped. Continuous scans or conversions can be stopped by writing a 1 to this bit. This will
immediately halt a conversion (even if the pen is still down)
and cause the A/D converter to power down. The default
state is continuous conversions, but if this bit is read after a
reset or power-up, it will read 1.
STS
The A/D Converter Control Register controls several aspects
of the A/D converter. The register is formatted as shown in
Table VI.
Bit 15: PSM—Pen Status/Control Mode. Reading this bit
allows the host to determine if the screen is touched. Writing
to this bit determines the mode used to read coordinates:
host controlled, or under control of the TSC2000 responding
to a screen touch. When reading, the PENSTS bit indicates
if the pen is down or not. When writing to this register, this bit
determines if the TSC2000 controls the reading of coordinates, or if the coordinate conversions are host-controlled.
The default state is host-controlled conversions (0).
Read
Read
Write
Write
VALUE
0
1
0
1
VALUE
Read
Read
Write
Write
0
1
0
1
DESCRIPTION
Converter is Busy
Conversions are Complete, Data is Available
Normal Operation
Stop Conversion and Power Down
TABLE VII. STS Bit Operation.
Bits [13:10]: AD3–AD0—A/D Converter Function Select
Bits. These bits control which input is to be converted, and
what mode the converter is placed in. These bits are the
same whether reading or writing. A complete listing of how
these bits are used is shown in Table VIII.
Bits[9:8]: RS1, RS0—Resolution Control. The A/D converter
resolution is specified with these bits. A description of these
bits is shown in Table IX. These bits are the same whether
reading or writing.
PSM
READ/WRITE
READ/WRITE
DESCRIPTION
No Screen Touch Detected
Screen Touch Detected
Conversions Controlled by Host
Conversions Controlled by TSC2000
TABLE V. PSM Bit Operation.
Bit 14: STS—A/D Converter Status. When reading this bit
indicates if the converter is busy, or if conversions are
complete and data is available. Writing a 0 to this bit will
cause touch screen scans to continue until either the pen is
RS1
RS0
FUNCTION
0
0
12-Bit Resolution. Power up and reset default.
0
1
8-Bit Resolution
1
0
10-Bit Resolution
1
1
12-Bit Resolution
TABLE IX. A/D Converter Resolution Control.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 0
PSM
STS
AD3
AD2
AD1
AD0
RS1
RS0
AV1
AV0
CL1
CL0
PV2
PV1
PV0
X
TABLE VI. A/D Converter Control Register.
A/D3
A/D2
A/D1
A/D0
0
0
0
0
0
0
0
1
0
0
1
0
0
0
0
0
0
1
1
1
1
0
1
1
1
1
0
0
0
0
1
0
0
1
1
0
0
1
1
1
0
1
0
1
0
1
0
1
1
1
0
0
1
1
1
1
1
1
0
1
1
1
0
1
FUNCTION
Invalid. No registers will be updated. This is the default state after a reset.
Touch screen scan function: X and Y coordinates converted and the results returned to X and Y data registers.
Scan continues until either the pen is lifted or a stop bit is sent.
Touch screen scan function: X, Y, Z1, and Z2 coordinates converted and the results returned to X, Y, Z1, and Z2
data registers. Scan continues until either the pen is lifted or a stop bit is sent.
Touch screen scan function: X coordinate converted and the results returned to X data register.
Touch screen scan function: Y coordinate converted and the results returned to Y data register.
Touch screen scan function: Z1 and Z2 coordinates converted and the results returned to Z1 and Z2 data registers.
Battery Input 1 converted and the results returned to the BAT1 data register.
Battery Input 2 converted and the results returned to the BAT2 data register.
Auxiliary Input 1 converted and the results returned to the AUX1 data register.
Auxiliary Input 2 converted and the results returned to the AUX2 data register.
A temperature measurement is made and the results returned to the temperature measurement 1 data register.
Port scan function: Battery Input 1, Battery Input 2, Auxiliary Input 1, and a Auxiliary Input measurements are made
and the results returned to the appropriate data registers.
A differential temperature measurement is made and the results returned to the temperature measurement 2 data
register.
Turn on X+, X– drivers.
Turn on Y+, Y– drivers.
Turn on Y+, X– drivers.
TABLE VIII. A/D Converter Function Select.
TSC2000
SBAS257
www.ti.com
15
Bits[7:6]: AV1, AV0 = Converter Averaging Control. These
two bits allow you to specify the number of averages the
converter will perform, as shown in Table X. Note that when
averaging is used, the STS bit and the DAV output will
indicate that the converter is busy until all conversions
necessary for the averaging are complete. The default state
for these bits is 00, selecting no averaging. These bits are the
same whether reading or writing.
AV1
AV0
0
0
1
1
0
1
0
1
D/A CONVERTER CONTROL REGISTER
(PAGE 1, ADDRESS 02H)
The single bit in this register controls the power down control
of the on-board D/A converter. This register is formatted as
shown in Table XIII.
Bit 15: DPD = D/A Converter Power Down. This bit controls
whether the D/A converter is powered up and operational, or
powered down. If the D/A converter is powered down, the
AOUT pin will neither sink nor source current.
FUNCTION
None
4 Data Averages
8 Data Averages
16 Data Averages
DPD
VALUE
0
1
TABLE X. A/D Conversion Averaging Control.
DESCRIPTION
D/A Converter is Powered and Operational
D/A Converter is Powered Down
TABLE XIV. DPD Bit Operation.
Bits[5:4]: CL1, CL0 = Conversion Clock Control. These two
bits specify the internal clock rate which the A/D converter uses
when performing a single conversion, as shown in Table XI.
These bits are the same whether reading or writing.
CL1
CL0
0
0
1
1
0
1
0
1
FUNCTION
8MHz Internal Clock Rate—8-Bit Resolution Only
4MHz Internal Clock Rate—10-Bit Resolution Only
2MHz Internal Clock Rate.
1MHz Internal Clock Rate.
TABLE XI. A/D Converter Clock Control.
Bits [3:1]: PV2 – PV0 = Panel Voltage Stabilization Time
control. These bits allow you to specify a delay time from the
time a pen touch is detected to the time a conversion is
started. This allows you to select the appropriate settling time
for the touch panel used. Table XII shows the settings of
these bits. The default state is 000, indicating a 0ms stabilization time. These bits are the same whether reading or
writing.
Bit 0: This bit is not used, and is a “don’t care” when writing.
It will always read as a zero.
PV2
PV1
PV0
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
FUNCTION
0µs Stabilization Time
100µs Stabilization Time
500µs Stabilization Time
1ms Stabilization Time
5ms Stabilization Time
10ms Stabilization Time
50ms Stabilization Time
100ms Stabilization Time
REFERENCE REGISTER
(PAGE 1, ADDRESS 03H)
The TSC2000 has a register to control the operation of the
internal reference. This register is formatted as shown in
Table XV.
Bit 4: INT = Internal Reference Mode. If this bit is written to
a 1, the TSC2000 will use its internal reference; if this bit is
a zero, the part will assume an external reference is being
supplied. The default state for this bit is to select an external
reference (0). This bit is the same whether reading or writing.
INT
VALUE
0
1
DESCRIPTION
External Reference Selected
Internal Reference Selected
TABLE XVI. INT Bit Operation.
Bits [3:2]: DL1, DL0 = Reference Power-Up Delay. When
the internal reference is powered up, a finite amount of time
is required for the reference to settle. If measurements are
made before the reference has settled, these measurements
will be in error. These bits allow for a delay time for measurements to be made after the reference powers up, thereby
assuring that the reference has settled. Longer delays will be
necessary depending upon the capacitance present at the
REF pin (see Typical Characteristics).
See Table XVII for the delays. The default state for these bits
is 00, selecting a 0ms delay. These bits are the same
whether reading or writing.
TABLE XII. Panel Voltage Stabilization Time Control.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 0
DPD
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
TABLE XIII. D/A Converter Control Register.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 0
X
X
X
X
X
X
X
X
X
X
X
INT
DL1
DL0
PDN
RFV
TABLE XV. Reference Register.
16
TSC2000
www.ti.com
SBAS257
DL1
DL0
0
0
1
1
0
1
0
1
TSC2000 CONFIGURATION CONTROL REGISTER
(PAGE 1, ADDRESS 05H)
DELAY TIME
0µs
100µs
500µs
1000µs
This control register controls the configuration of the precharge
and sense times for the touch detect circuit. The register is
formatted as shown in Table XXI.
TABLE XVII. Reference Power-Up Delay Settings.
Bit 1: PDN = Reference Power Down. If a 1 is written to this
bit, the internal reference will be powered down between
conversions. If this bit is a zero, the internal reference will be
powered at all times. The default state is to power down the
internal reference, so this bit will be a 1. This bit is the same
whether reading or writing.
Bits [5:3]: PRE[2:0] = Precharge Time Selection Bits. These
bits set the amount of time allowed for precharging any pin
capacitance on the touch screen prior to sensing if a screen
touch is happening.
PRE[2:0]
PRE2
PRE1
PRE0
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
PDN
VALUE
DESCRIPTION
0
1
Internal Reference is Powered at All Times
Internal Reference is Powered Down Between Conversions
TABLE XVIII. PDN Bit Operation.
TIME
20µs
84µs
276µs
340µs
1.044ms
1.108ms
1.300ms
1.364ms
TABLE XXII. Precharge Times.
Note that the PDN bit, in concert with the INT bit, creates a
few possibilities for reference behavior. These are detailed in
Table XIX.
INT
PDN
REFERENCE BEHAVIOR
0
0
External Reference Used, Internal Reference Powered Down
0
1
External Reference Used, Interenal Reference Powered Down
1
1
0
1
Internal Reference Used, Always Powered Up
Internal Reference Used, Will Power Up During Conversions
Bits [2:0]: SNS[2:0] = Sense Time Selection Bits. These bits
set the amount of time the TSC2000 will wait to sense a
screen touch between coordinate axis conversions in
PENIRQ-controlled mode.
SNS[2:0]
SNS2
SNS1
SNS0
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
and Then Power Down
TABLE XIX. Reference Behavior Possibilities.
Bit 0: RFV = Reference Voltage control. This bit selects the
internal reference voltage, either 1.25V or 2.5V. The default
value is 1.25V. This bit is the same whether reading or writing.
TIME
32µs
96µs
544µs
608µs
2.080ms
2.144ms
2.592ms
2.656ms
TABLE XXIII. Sense Times.
RFV
VALUE
DESCRIPTION
0
1
1.25V Reference Voltage
2.5V Reference Voltage
TABLE XX. RFV Bit Operation.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 0
X
X
X
X
X
X
X
X
X
X
PRE2
PRE1
PRE0
SNS2
SNS1
SNS0
TABLE XXI. Configuration Control Register.
TSC2000
SBAS257
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17
RESET REGISTER
(PAGE 1, ADDRESS 04H)
ZERO REGISTER
(PAGE 0, ADDRESS 10H)
The TSC2000 has a special register, the RESET register, which
allows a software reset of the device. Writing the code BBXXH,
as shown in Table XXIV, to this register will cause the TSC2000
to reset all its registers to their default, power-up values.
This is a reserved data register, but instead of reading all 1’s
(FFFFH), when read will return all 0’s (0000H).
Writing any other values to this register will do nothing.
Reading this register or any reserved register will result in
reading back all 1’s, or FFFFH.
As noted previously in the discussion of the A/D converter,
several operating modes can be used, which allow great
flexibility for the host processor. These different modes will
now be examined.
TSC2000 DATA REGISTERS
Conversion Controlled by TSC2000 Initiated at
Touch Detect
The data registers of the TSC2000 hold data results from
conversions or keypad scans, or the value of the D/A converter
output current. All of these registers default to 0000H upon reset,
except the D/A converter register, which is set to 0080H,
representing the midscale output of the D/A converter.
X, Y, Z1, Z2, BAT1, BAT2, AUX1, AUX2, TEMP1,
AND TEMP2 REGISTERS
The results of all A/D conversions are placed in the appropriate data register, see Tables III and VIII. The data format of
the result word, R, of these registers is right-justified, as
shown in Table XXV.
D/A CONVERTER DATA REGISTER
(PAGE 0, ADDRESS 0BH)
The data to be written to the D/A converter is written into the
D/A converter data register, which is formatted as shown in
Table XXVI.
OPERATION—TOUCH SCREEN MEASUREMENTS
In this mode, the TSC2000 will detect when the touch panel is
touched and cause the PENIRQ line to go LOW. At the same
time, the TSC2000 will start up its internal clock. It will then turn
on the Y-drivers, and after a programmed Panel Voltage
Stabilization time, power up the A/D converter and convert the
Y-coordinate. If averaging is selected, several conversions
may take place; when data averaging is complete, the Ycoordinate result will be stored in the Y-register.
If the screen is still touched at this time, the X-drivers will be
enabled, and the process will repeat, but instead measuring
the X-coordinate and storing the result in the X-register.
If only X- and Y-coordinates are to be measured, then the
conversion process is complete. See Figure 8 for a flowchart
for this process. The time it takes to go through this process
depends upon the selected resolution, internal conversion
clock rate, averaging selected, panel voltage stabilization
time, and precharge and sense times.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 0
1
0
1
1
1
0
1
1
X
X
X
X
X
X
X
X
LSB
BIT 0
TABLE XXIV. Reset Register.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
0
0
0
0
R11
MSB
R10
R9
R8
R7
R6
R5
R4
R3
R2
R1
R0
LSB
TABLE XXV. Result Data Format.
MSB
BIT 15
BIT 14
BIT 13
BIT 12
BIT 11
BIT 10
BIT 9
BIT 8
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 0
X
X
X
X
X
X
X
X
D7
D6
D5
D4
D3
D2
D1
D0
TABLE XXVI. D/A Converter Register.
18
TSC2000
www.ti.com
SBAS257
The time needed to get a complete X/Y-coordinate reading
can be calculated by:
(3)
1
tCOORDINATE = 2.5 µs + 2( tPVS + tPRE + tSNS ) + 2NAVG NBITS •
+ 4.4µs
fCONV
where,
tCOORDINATE = time to complete X/Y-coordinate reading
tPVS = Panel Voltage Stabilization time, see Table XII
tPRE = precharge time, see Table XXII
NBITS = number of bits of resolution, see Table IX
fCONV = A/D converter clock frequency, see Table XI
If the pressure of the touch is also to be measured, the
process will continue in the same way, but measuring the Z1
and Z2 values, and placing them in the Z1 and Z2 registers,
see Figure 9. As before, this process time depends upon the
settings described above. The time for a complete X, Y, Z1,
and Z2 coordinate reading is given by:
(4)
1
tCOORDINATE = 4.75µs + 3( tPVS + tPRE + tSNS ) + 4NAVG NBITS •
+ 4.4µs
fCONV
tSNS = sense time, see Table XXIII
NAVG = number of averages, see Table X; for no averaging, NAVG = 1
Touch Screen Scan
X and Y
PENIRQ Initiated
Screen
Touch
Turn On Drivers: X+, X–
Issue Interrupt
PENIRQ
No
No
Is PSM = 1
Go to Host-Controlled
Conversion
Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
Yes
Start Clock
Convert X-Coordinates
Turn On Drivers: Y+, Y–
No
No
Is Panel Voltage
Stabilization Done
Yes
Is Data
Averaging Done
Yes
Store X-Coordinates in
X-Register
Power Up A/D Converter
Convert Y-Coordinates
Power Down A/D Converter
No
Issue Data Available
Is Data
Averaging Done
Yes
Yes
Store Y-Coordinates in
Y-Register
Is Screen
Touched
No
Power Down A/D Converter
Is Screen
Touched
No
Turn Off Clock
Turn Off Clock
Reset PENIRQ and
Scan Trigger
Reset PENIRQ and
Scan Trigger
Done
Done
Yes
FIGURE 8. X- and Y-Coordinate Touch Screen Scan, Initiated by Touch.
TSC2000
SBAS257
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19
Turn On Drivers: Y+, X–
Touch Screen Scan
X, Y, and Z
PENIRQ Initiated
No
Screen
Touch
Is Panel Voltage
Stabilization Done
Yes
Turn On Drivers: X+, X–
Issue Interrupt
PENIRQ
Power Up A/D Converter
No
Is PSM = 1
No
Go to Host-Controlled
Conversion
Is Panel Voltage
Stabilization Done
Convert Z1-Coordinates
Yes
Yes
No
Start Clock
Power Up A/D Converter
Turn On Drivers: Y+, Y–
Convert X-Coordinates
Is Data
Averaging Done
Yes
Store Z1-Coordinates
in Z1-Register
No
Is Panel Voltage
Stabilization Done
No
Is Data
Averaging Done
Convert Z2-Coordinates
Yes
Yes
Power Up A/D Converter
No
Store X-Coordinates
in X-Register
Convert Y-Coordinates
Is Data
Averaging Done
Yes
Power Down A/D Converter
Turn Off Clock
Store Z2-Coordinates
in Z2-Register
No
Is Data
Averaging Done
Is Screen
Touched
Reset PENIRQ and
Scan Trigger
Power Down A/D Converter
Yes
Done
Store Y-Coordinates in
Y-Register
Issue Data Available
Power Down A/D Converter
Is Screen
Touched
Turn Off Clock
No
Yes
Reset PENIRQ and
Scan Trigger
Is Screen
Touched
No
Turn Off Clock
Done
Yes
Reset PENIRQ and
Scan Trigger
Done
FIGURE 9. X-, Y-, and Z-Coordinate Touch Screen Scan, Initiated by Touch.
20
TSC2000
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SBAS257
Conversion Controlled by TSC2000 Initiated By
Host Responding to PENIRQ
scan functions. The conversion process then proceeds as
described above, and as outlined in Figures 10 through 14.
In this mode, the TSC2000 will detect when the touch panel is
touched and cause the PENIRQ line to go LOW. The host will
recognize the interrupt request, and then write to the A/D
Converter Control register to select one of the touch screen
The main difference between this mode and the previous
mode is that the host, not the TSC2000, decides when the
touch screen scan begins.
Screen
Touch
Touch Screen Scan
X and Y
Host Initiated
Issue Interrupt
PENIRQ
No
Is PSM = 1
Go to Host-Controlled
Conversion
Done
Host Writes A/D
Converter
Control Register
Turn On Drivers: X+, X–
Reset PENIRQ
No
Is Panel Voltage
Stabilization Done
Start Clock
Yes
Power Up A/D Converter
Turn On Drivers: Y+, Y–
Convert X-Coordinates
No
Is Panel Voltage
Stabilization Done
Yes
No
Is Data
Averaging Done
Power Up A/D Converter
Yes
Convert Y-Coordinates
Store X-Coordinates
in X-Register
No
Is Data
Averaging Done
Power Down A/D Converter
Yes
Issue Data Available
Store Y-Coordinates in
Y-Register
Yes
Power Down A/D Converter
Is Screen
Touched
Turn Off Clock
No
Is Screen
Touched
No
Reset PENIRQ and
Scan Trigger
Turn Off Clock
Done
Done
Yes
FIGURE 10. X- and Y-Coordinate Touch Screen Scan, Initiated by Host.
TSC2000
SBAS257
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21
Screen
Touch
Touch Screen Scan
X, Y, and Z
Host Initiated
Issue Interrupt
PENIRQ
Turn On Drivers: Y+, X–
No
No
Is PSM = 1
Go to Host-Controlled
Conversion
Turn On Drivers: X+, X–
Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
Done
No
Host Writes A/D
Converter
Control Register
Is Panel Voltage
Stabilization Done
Convert Z1-Coordinates
Yes
Reset PENIRQ
Power Up A/D Converter
No
Is Data
Averaging Done
Start Clock
Convert X-Coordinates
Yes
Store Z1-Coordinates
in Z1-Register
Turn On Drivers: Y+, Y–
No
No
Is Data
Averaging Done
Convert Z2-Coordinates
Is Panel Voltage
Stabilization Done
Yes
Store X-Coordinates
in X-Register
Yes
No
Is Data
Averaging Done
Power Up A/D Converter
Power Down A/D Converter
Yes
Turn Off Clock
Convert Y-Coordinates
Store Z2-Coordinates
in Z2-Register
Is Screen
Touched
No
No
Reset PENIRQ and
Scan Trigger
Is Data
Averaging Done
Power Down A/D Converter
Yes
Done
Yes
Issue Data Available
Store Y-Coordinates in
Y-Register
Yes
Power Down A/D Converter
Is Screen
Touched
Turn Off Clock
No
Is Screen
Touched
No
Turn Off Clock
Reset PENIRQ and
Scan Trigger
Done
Done
Yes
FIGURE 11. X-, Y-, and Z-Coordinate Touch Screen Scan, Initiated by Host.
22
TSC2000
www.ti.com
SBAS257
Screen
Touch
Touch Screen Scan
X-Coordinate
Host Initiated
Issue Interrupt
PENIRQ
No
Is PSM = 1
Go to Host-Controlled
Conversion
Convert X-Coordinates
Done
No
Host Writes A/D
Converter
Control Register
Is Data
Averaging Done
Yes
Reset PENIRQ
Store X-Coordinates
in X-Register
No
Start Clock
Are Drivers On
Yes
Turn On Drivers: X+, X–
Power Down A/D Converter
Issue Data Available
Turn Off Clock
Start Clock
No
Is Panel Voltage
Stabilization Done
Done
Yes
Power Up A/D Converter
FIGURE 12. X-Coordinate Reading Initiated by Host.
TSC2000
SBAS257
www.ti.com
23
Screen
Touch
Touch Screen Scan
Y-Coordinate
Host Initiated
Issue Interrupt
PENIRQ
No
Is PSM = 1
Go to Host-Controlled
Conversion
Store Y-Coordinates
in Y-Register
Done
Power Down A/D Converter
Host Writes A/D
Converter
Control Register
Issue Data Available
Reset PENIRQ
Turn Off Clock
Are Drivers On
Done
No
Start Clock
Yes
Turn On Drivers: Y+, Y–
Start Clock
No
Power Up A/D Converter
Is Panel Voltage
Stabilization Done
Yes
Convert Y-Coordinates
No
Is Data
Averaging Done
Yes
FIGURE 13. Y-Coordinate Reading Initiated by Host.
24
TSC2000
www.ti.com
SBAS257
Screen
Touch
Touch Screen Scan
Z-Coordinate
Host Initiated
Issue Interrupt
PENIRQ
No
Is PSM = 1
Go to Host-Controlled
Conversion
Convert Z2-Coordinates
Done
Host Writes A/D
Converter
Control Register
No
Reset PENIRQ
Are Drivers On
Is Data
Averaging Done
Yes
Store Z2-Coordinates
in Z2-Register
No
Start Clock
Power Down A/D Converter
Turn On Drivers: Y+, X–
Yes
Issue Data Available
Start Clock
No
Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
Turn Off Clock
Done
Convert Z1-Coordinates
No
Is Data
Averaging Done
Yes
Store Z1-Coordinates
in Z1-Register
FIGURE 14. Z-Coordinate Reading Initiated by Host.
TSC2000
SBAS257
www.ti.com
25
Conversion Controlled by the Host
In this mode, the TSC2000 will detect when the touch panel
is touched and cause the PENIRQ line to go LOW. The host
will recognize the interrupt request. Instead of starting a
sequence in the TSC2000 which then reads each coordinate
in turn, the host now must control all aspects of the conversion. Generally, upon receiving the interrupt request, the host
will turn on the Y-drivers. After waiting for the settling time,
the host will then address the TSC2000 again, this time
requesting an X-coordinate conversion.
The process is then repeated for Y- and Z-coordinates. The
processes are outlined in Figures 15 through 17.
The time needed to convert any single coordinate under host
control (not including the time needed to send the command
over the SPI bus) is given by:
(5)
1
tCOORDINATE = 2.125µs + tPVS + NAVG NBITS •
+ 4.4µs
fCONV
Host-Controlled
X-Coordinate
Screen
Touch
Host Writes A/D
ConverterControl Register
Issue Interrupt
PENIRQ
No
Start Clock
No
Is PSM = 1
Go to Host-Controlled
Conversion
Are Drivers On
Yes
Turn On Drivers: X+, X–
Start Clock
Done
Host Writes A/D
Converter
Control Register
Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
Convert X-Coordinates
No
Reset PENIRQ
Turn On Drivers: X+, X–
No
Done
Is Data
Averaging Done
Yes
Store X-Coordinates
in X-Register
Power Down A/D Converter
Issue Data Available
Turn Off Clock
Done
FIGURE 15. X-Coordinate Reading Controlled by Host.
26
TSC2000
www.ti.com
SBAS257
Host-Controlled
Y-Coordinate
Screen
Touch
Host Writes A/D
Converter
Control Register
Issue Interrupt
PENIRQ
No
Start Clock
No
Is PSM = 1
Go to Host-Controlled
Conversion
Are Drivers On
Yes
Turn On Drivers: Y+, Y–
Start Clock
Done
Host Writes A/D
Converter
Control Register
Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
Convert Y-Coordinate
No
Reset PENIRQ
Turn On Drivers: Y+, Y–
No
Done
Is Data
Averaging Done
Yes
Store Y-Coordinates
in Y-Register
Power Down A/D Converter
Issue Data Available
Turn Off Clock
Done
FIGURE 16. Y-Coordinate Reading Controlled by Host.
TSC2000
SBAS257
www.ti.com
27
Screen
Touch
Host-Controlled
Z-Coordinate
Issue Interrupt
PENIRQ
No
Is PSM = 1
Convert Z2-Coordinates
Go to Host-Controlled
Conversion
Done
No
Host Writes A/D
Converter
Control Register
Is Data
Averaging Done
Yes
Reset PENIRQ
Store Z2-Coordinates
in Z2-Register
Turn On Drivers: Y+, X–
Power Down A/D Converter
Done
Issue Data Available
Host Writes A/D
Converter
Control Register
Turn Off Clock
Reset PENIRQ
Done
Is Data
Averaging Done
No
Start Clock
Turn On Drivers: Y+, X–
Yes
Start Clock
No
Is Panel Voltage
Stabilization Done
Yes
Power Up A/D Converter
Convert Z1-Coordinates
No
Is Data
Averaging Done
Yes
Store Z1-Coordinates
in Z1-Register
FIGURE 17. Z-Coordinate Reading Controlled by Host.
28
TSC2000
www.ti.com
SBAS257
OPERATION—TEMPERATURE MEASUREMENT
In some applications, such as battery recharging, a measurement of ambient temperature is required. The temperature
measurement technique used in the TSC2000 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 TSC2000 offers two modes of temperature measurement.
The first mode requires calibration at a known temperature, but
only requires a single reading to predict the ambient temperature. A diode, as shown in Figure 18, is used during this
measurement cycle. 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; 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 system memory, for calibration
purposes by the user. The result is an equivalent temperature
measurement resolution of 0.3°C/LSB. This measurement of
what is referred to as Temperature 1 is illustrated in Figure 19.
Host Writes
A/D Converter
Control Register
Temperature Input 1
Start Clock
Power Up Reference
Power Up
A/D Converter
Convert
Temperature Input 1
No
Is Data
Averaging Done
Yes
Store Temperature
Input 1 in TEMP1
Register
Power Down
A/D Converter
Power Down Reference
Issue Data Available
Turn Off Clock
Done
FIGURE 19. Single Temperature Measurement Mode.
X+
MUX
A/D
Converter
Host Writes
A/D Converter
Control Register
Temperature Input 2
Start Clock
Temperature Select
TEMP1
TEMP2
Power Up Reference
FIGURE 18. Functional Block Diagram of Temperature Measurement Mode.
Power Up
A/D Converter
The second mode does not require a test temperature
calibration, but uses a two-measurement (differential) method
to eliminate the need for absolute temperature calibration
and for achieving 2°C/LSB accuracy. This mode requires a
second conversion with a 91 times larger current. The
voltage difference between the first (TEMP1) and second
(TEMP2) conversion, using 91 times the bias current, will be
represented by kT/q •ln (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
method can provide much improved absolute temperature
measurement, but less resolution of 2°C/LSB. The resultant
equation for solving for °K is:
°K =
where,
q • ∆V
k • ln(N)
∆V = V(I91) − V(I1)
(6)
Convert
Temperature Input 2
No
Is Data
Averaging Done
Yes
Store Temperature
Input 2 in TEMP2
Register
Power Down
A/D Converter
Power Down Reference
Issue Data Available
Turn Off Clock
Done
FIGURE 20. Additional Temperature Measurement for Differential Temperature Reading.
(in mV)
∴ °K = 2.573∆V°K/mV
°C = 2.573 • ∆V(mV) − 273°K
See Figure 20 for the Temperature 2 measurement.
TSC2000
SBAS257
www.ti.com
29
OPERATION—BATTERY MEASUREMENT
Host Writes
A/D Converter
Control Register
An added feature of the TSC2000 is the ability to monitor the
battery voltage on the other side of a voltage regulator (DC/
DC converter), as shown in Figure 21. The VBAT1 input is
divided down by 4 so that an input range of 0.5V to 6.0V can
be measured. Because of the division by 4, this input range
would be represented as 0.125V to 1.5V to the A/D converter.
Battery Input 1
Start Clock
Power Up Reference
Power Up
A/D Converter
Power Down
A/D Converter
2.7V
DC/DC
Converter
Battery
0.5V +
to
6.0V
Convert
Battery Input 1
Power Down Reference
VDD
No
Issue Data Available
Is Data
Averaging Done
Turn Off Clock
Yes
0.125V to 1.5V
VBAT1
Store Battery Input 1
in BAT1 Register
7.5kΩ
Done
2.5kΩ
FIGURE 22. VBAT1 Measurement Process.
Host Writes
A/D Converter
Control Register
FIGURE 21. Battery Measurement Functional Block Diagram.
Battery Input 2
The VBAT2 input is divided down by 2, so it accommodates an
input range of 0.5V to 3.0V, which is represented to the A/D
converter as 0.25V to 1.5V. This smaller divider ratio allows
for increased resolution. Note that the VBAT2 input pin can
withstand up to 6V, but this input will only provide accurate
measurements within the 0.5V to 3.0V range.
Start Clock
Power Up Reference
Power Up
A/D Converter
For both battery inputs, the dividers are ON only during the
sampling of the battery input, in order to minimize power
consumption.
Convert
Battery Input 2
Flowcharts which detail the process of making a battery input
reading are shown in Figures 22 and 23.
The time needed to make temperature, auxiliary, or battery
measurements is given by:
(7)
tREADING = 2.625µs + tREF
No
1
+ NAVG NBITS •
+ 4.4µs
f
CONV
Power Down
A/D Converter
Power Down Reference
Is Data
Averaging Done
Yes
Store Battery Input 2
in BAT2 Register
where tREF is the reference delay time as given in Table XVII.
Issue Data Available
Turn Off Clock
Done
FIGURE 23. VBAT2 Measurement Process.
30
TSC2000
www.ti.com
SBAS257
OPERATION—AUXILIARY MEASUREMENT
OPERATION—PORT SCAN
The two auxiliary voltage inputs can be measured in much
the same way as the battery inputs, as shown in Figures 24
and 25. Applications might include external temperature
sensing, ambient light monitoring for controlling the backlight, or sensing the current drawn from the battery.
If making measurements of all the analog inputs (except the
touch screen) is desired on a periodic basis, the Port Scan
mode can be used. This mode causes the TSC2000 to
sample and convert both battery inputs and both auxiliary
inputs. At the end of this cycle, the battery and auxiliary result
registers will contain the latest values. Thus, with one write
to the TSC2000, the host can cause four different measurements to be made.
Host Writes
A/D Converter
Control Register
The flowchart for this process is shown in Figure 26. The time
needed to make a complete port scan is given by:
Auxiliary Input 1
Start Clock
tREADING = 7.5µs + tREF + 4NAVG NBITS
Power Up Reference
•
1
fCONV
+ 4.4µs (8)
Power Up
A/D Converter
Port Scan
Power Down
A/D Converter
Convert
Auxiliary Input 1
Power Down Reference
No
Is Data
Averaging Done
Convert
Auxiliary Input 1
Host Writes
A/D Converter
Control Register
Issue Data Available
Start Clock
No
Turn Off Clock
Yes
Is Data
Averaging Done
Power Up Reference
Store Auxiliary Input 1
in AUX1 Register
Yes
Done
Power Up
A/D Converter
Store Auxiliary Input 1
in AUX1 Register
Convert
Battery Input 1
FIGURE 24. AUX1 Measurement Process.
Host Writes
A/D Converter
Control Register
No
Is Data
Averaging Done
Auxiliary Input 2
Convert
Auxiliary Input 2
No
Is Data
Averaging Done
Yes
Start Clock
Yes
Power Up Reference
Store Battery Input 1
in BAT1 Register
Power Up
A/D Converter
Convert
Battery Input 2
Power Down
A/D Converter
Convert
Auxiliary Input 2
No
Power Down Reference
Is Data
Averaging Done
Store Auxiliary Input 2
in AUX2 Register
Power Down
A/D Converter
Power Down Reference
Issue Data Available
No
Is Data
Averaging Done
Yes
Store Auxiliary Input 2
in AUX2 Register
FIGURE 25. AUX2 Measurement Process.
Issue Data Available
Yes
Store Battery Input 2
in BAT2 Register
Turn Off Clock
Done
Done
FIGURE 26. Port Scan Mode.
TSC2000
SBAS257
Turn Off Clock
www.ti.com
31
OPERATION—D/A CONVERTER
The TSC2000 has an on-board 8-bit D/A converter, configured as shown in Figure 27. This configuration yields a
current sink (AOUT) controlled by the value of a resistor
connected between the ARNG pin and ground. The D/A
converter has a control register, which controls whether or
not the converter is powered up. The 8-bit data is written to
the D/A converter through the D/A converter data register.
0.9
IOUT (Full-Scale) (mA)
0.8
V+
0.7
0.6
0.5
0.4
0.3
0.2
0.1
R1
0
10k
VBIAS
1M
10M
100M
ARNG Resistor (Ω)
R2
FIGURE 28. D/A Converter Output Current Range versus
RRNG Resistor Value.
AOUT
8 Bits
100k
D/A Converter
For example, consider an LCD that has a contrast control
voltage VBIAS that can range from 2V to 4V, that draws 400µA
when used, and an available +5V supply. Note that this is
higher than the TSC2000 supply voltage, but it is within the
absolute maximum ratings.
ARNG
RRNG
The maximum VBIAS voltage is 4V, and this occurs when the
D/A converter current is 0, so only the 400µA load current
ILOAD will be flowing from 5V to VBIAS. This means 1V will be
dropped across R1, so R1 = 1V/400µA = 2.5kΩ.
FIGURE 27. D/A Converter Configuration.
This circuit is designed for flexibility in the output voltage at the
VBIAS point shown in Figure 27 to accommodate the widely
varying requirements for LCD contrast control bias. V+ can be
a higher voltage than the supply voltage for the TSC2000. The
only restriction is that the voltage on the AOUT pin can never go
above the absolute maximum ratings for the device, and
should stay above 1.5V for linear operation.
The minimum VBIAS is 2V, which occurs when the D/A
converter current is at its full scale value, IMAX. In this case,
5V – 2V = 3V will be dropped across R1, so the current
through R1 will be 3V/2.5K = 1.2mA. This current is
IMAX + ILOAD = IMAX + 400uA, so IMAX must be set to 800µA.
Looking at Figure 28, this means that RRNG should be
around 1MΩ.
The D/A converter has an output sink range which is limited to
1mA. This range can be adjusted by changing the value of
RRNG shown in Figure 27. As this D/A converter is not
designed to be a precision device, the actual output current
range can vary as much as ±20%. Furthermore, the current
output will change due to variations in temperature; the D/A
converter has a temperature coefficient of approximately
–2µA/°C. To set the full-scale current, RRNG can be determined from the graph shown in Figure 28.
Since the voltage at the AOUT pin should not go below 1.5V,
this limits the voltage at the bottom of R2 to be 1.5V
minimum; this occurs when the D/A converter is providing its
maximum current, IMAX. In this case, IMAX +ILOAD flows through
R1, and IMAX flows through R2. Thus,
32
R2IMAX + R1(IMAX + ILOAD) = 5V – 1.5V = 3.5V
We already have found R1 = 2.5kΩ, IMAX = 800µA,
ILOAD = 400µA, so we can solve this for R2 and find that it
should be 625Ω.
TSC2000
www.ti.com
SBAS257
In the previous example, when the D/A converter current is
zero, the voltage on the AOUT pin will rise above the TSC2000
supply voltage. This is not a problem, however, since V+ was
within the absolute maximum ratings of the TSC2000, so no
special precautions are necessary. Many LCD displays require voltages much higher than the absolute maximum
ratings of the TSC2000. In this case, the addition of an NPN
transistor, as shown in Figure 29, will protect the AOUT pin
from damage.
V+
R1
VBIAS
R2
VSUPPLY
With this in mind, power to the TSC2000 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 +VDD and the power supply is HIGH.
A bypass capacitor is generally not needed on the reference
pin because the 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 TSC2000 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.
AOUT
8 Bits
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.
D/A Converter
ARNG
RRNG
FIGURE 29. D/A Converter Circuit when Using V+ Higher
than VSUPPLY.
LAYOUT
The following layout suggestions should provide optimum
performance from the TSC2000. 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.
For optimum performance, care should be taken with the
physical layout of the TSC2000 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
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 or battery connection point. The ideal layout will include
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. Since resistive touch screens have
fairly low resistance, the interconnection should be as short
and robust as possible. 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
back-lit 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. Note, however, that
the use of these capacitors will increase screen settling time
and require longer panel voltage stabilization times, as well
as increased precharge and sense times for the PENIRQ
circuitry of the TSC2000.
TSC2000
SBAS257
www.ti.com
33
PACKAGE OPTION ADDENDUM
www.ti.com
14-Oct-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)
TSC2000IPW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC2000I
Samples
TSC2000IPWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
TSC2000I
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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