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.
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) ....................................................
ELECTRICAL CHARACTERISTICS At –40°C to +85°C, +VDD = +2.7V, internal VREF = +2.5V, conversion clock = 2MHz, 12-bit mode, unless otherwise noted.
TIMING CHARACTERISTICS(1)(2) At –40°C to +85°C, +VDD = +2.7V, VREF = +2.5V, unless otherwise noted.
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.
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.
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.
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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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 T
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.
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.
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-C
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.
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
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 I
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.
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.
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.
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.
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.
PACKAGE OPTION ADDENDUM www.ti.
PACKAGE OPTION ADDENDUM www.ti.
PACKAGE MATERIALS INFORMATION www.ti.com 26-Jan-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device TSC2000IPWR Package Package Pins Type Drawing TSSOP PW 20 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2000 330.0 16.4 Pack Materials-Page 1 6.95 B0 (mm) K0 (mm) P1 (mm) 7.1 1.6 8.0 W Pin1 (mm) Quadrant 16.
PACKAGE MATERIALS INFORMATION www.ti.com 26-Jan-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) TSC2000IPWR TSSOP PW 20 2000 367.0 367.0 38.
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