19-2512; Rev 4; 3/08 KIT ATION EVALU E L B AVAILA 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller The MAX1233/MAX1234 are complete PDA controllers in 5mm x 5mm, 28-pin QFN and TQFN packages. They feature a 12-bit analog-to-digital converter (ADC), low onresistance switches for driving resistive touch screens, an internal +1.0V/+2.5V or external reference, 2C accurate, on-chip temperature sensor, direct +6V battery monitor, keypad controller, 8-bit digital-to-analog converter (DAC), and a synchronous serial interface. Each of the keypad controllers' eight row and column inputs can be reconfigured as general-purpose parallel I/O pins (GPIO). All analog inputs are fully ESD protected, eliminating the need for external TransZorbTM devices. The MAX1233/MAX1234 offer programmable resolution and sampling rates. Interrupts from the devices alert the host processor when data is ready, when the screen is touched, or a key press is detected. Softwareconfigurable scan control and internal timers give the user flexibility without burdening the host processor. These devices consume only 260A at the maximum sampling rate of 50ksps. Supply current falls to below 50A for sampling rates of 10ksps. The MAX1233/MAX1234 are guaranteed over the -40C to +85C temperature range. Applications Personal Digital Assistants ESD-Protected Analog Inputs 15kV IEC 1000-4-2 Air-Gap Discharge 8kV IEC 1000-4-2 Contact Discharge Single-Supply Operation +2.7V to +3.6V (MAX1233) +4.75V to +5.25V (MAX1234) 4-Wire Touch-Screen Interface Internal +1.0V/+2.5V Reference or External Reference (+1.0V to AVDD) SPITM/QSPITM/MICROWIRETM-Compatible 10MHz Serial Interface 12-Bit, 50ksps ADC Measures Resistive Touch-Screen Position and Pressure Two Auxiliary Analog Inputs Two Battery Voltages (0.5V to 6V) On-Chip Temperature 8-Bit DAC for LCD Bias Control 4 x 4 Keypad Programmable Controller Offers Up to Eight GPIO Pins Automatic Detection of Screen Touch, Key Press, and End of Conversion Programmable 8-, 10-, 12-Bit Resolution Pagers Programmable Conversion Rates Touch-Screen Monitors AutoShutdownTM Between Conversions Cellular Phones Low Power 260A at 50ksps 50A at 10ksps 6A at 1ksps 0.3A Shutdown Current MP3 Players Portable Instruments Point-of-Sale Terminals CS SCLK DIN BUSY DOUT PENIRQ KEYIRQ 28 27 26 25 24 23 22 Pin Configuration TOP VIEW Features 28-Pin 5mm x 5mm QFN and TQFN Packages Ordering Information PART TEMP RANGE PIN-PACKAGE DVDD 1 21 C4 AVDD 2 20 C3 *X+ 3 19 C2 MAX1233ETI -40C to +85C 28 TQFN (5mm x 5mm) *Y+ 4 18 C1 MAX1234EGI -40C to +85C 28 QFN (5mm x 5mm) *X- 5 17 R1 *Y- 6 16 R2 MAX1234ETI -40C to +85C 28 TQFN (5mm x 5mm) GND 7 15 R3 10 11 12 13 14 *AUX2 REF DACOUT R4 9 *BAT2 *AUX1 8 *BAT1 MAX1233 MAX1234 QFN/TQFN *PIN INCLUDES 8kV/15kV ESD PROTECTION. MAX1233EGI -40C to +85C 28 QFN (5mm x 5mm) TransZorb is a trademark of General Semiconductor Industries, Inc. SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp. AutoShutdown is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX1233/MAX1234 General Description MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller ABSOLUTE MAXIMUM RATINGS AVDD to GND............................................................-0.3V to +6V DVDD to AVDD .......................................................-0.3V to +0.3V Digital Inputs/Outputs to GND .................-0.3V to (DVDD + 0.3V) X+, Y+, X-, Y-, AUX1, AUX2, and REF to GND ..................................-0.3V to (AVDD + 0.3V) BAT1, BAT2 to GND .................................................-0.3V to +6V Maximum ESD per IEC 1000-4-2 (per MIL STD-883 HBM) X+, X-, Y+, Y-, AUX1, AUX2, BAT1, BAT2......................15kV All Other Pins.....................................................................2.5kV Maximum Current into Any Pin............................................50mA Continuous Power Dissipation (TA = +70C) 28-Pin QFN (derate 28.5mW/C above +70C) .................2W 28-Pin TQFN (derate 28.5mW/C above +70C) ...............2W Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10s) .................................+300C Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 12 Bits ANALOG-TO-DIGITAL CONVERTER DC ACCURACY (Note 1) Resolution Software-programmable 8/10/12 bit No Missing Codes 11 Relative Accuracy (Note 2) INL Differential Nonlinearity DNL Offset Error Gain Error (Note 3) Total Unadjusted Error TUE Bits 12-bit mode 0.8 10-bit and 8-bit modes 0.5 12-bit mode 0.8 10-bit and 8-bit modes 0.5 12-bit mode 0.5 10-bit and 8-bit modes 0.5 12-bit mode 0.5 10-bit mode 0.5 8-bit mode 0.5 12-bit mode 2 10-bit and 8-bit modes 1 2 2 4 LSB LSB LSB 4 LSB LSB Offset Temperature Coefficient 0.4 ppm/C Gain Temperature Coefficient 0.4 ppm/C Channel-to-Channel Offset 0.1 LSB Channel-to-Channel Gain Matching 0.1 LSB 50 VRMS Noise Power-Supply Rejection Including internal VREF PSR Full-scale input MAX1233 AVDD = DVDD = +2.7V to +3.6V 0.4 MAX1234 AVDD = DVDD = +5V 5% 0.3 mV DYNAMIC SPECIFICATIONS (1kHz SINE WAVE, VIN = 2.5VP-P FOR MAX1233, VIN = 4.096VP-P FOR MAX1234, 50ksps, fSCLK = 10MHz) Signal-to-Noise Plus Distortion 2 SINAD 69 _______________________________________________________________________________________ dB 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller (DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL Total Harmonic Distortion THD Spurious-Free Dynamic Range SFDR CONDITIONS MIN TYP MAX -84 UNITS dB 84 dB Full-Power Bandwidth -3dB point 0.5 MHz Full-Linear Bandwidth SINAD > 67dB 50 kHz CONVERSION RATE Internal Oscillator Frequency 8 11.5 MHz Aperture Delay 30 ns Aperture Jitter <50 ps Maximum Serial Clock Frequency fSCLK 10 Duty Cycle MHz 30 70 % 0 VREF V 1 A AUXILIARY ANALOG INPUTS (AUX1, AUX2) Input Voltage Range Channel not selected or conversion stopped Input Leakage Current 0.1 Input Capacitance 34 pF BATTERY MONITOR INPUTS (BAT1, BAT2) Input Voltage Range 0.5 6.0 Sampling battery Input Impedance 10 Battery monitor OFF Accuracy Internal reference 1 -3 V k G +3 % +85 C TEMPERATURE MEASUREMENT Temperature Range -40 Resolution Accuracy Differential method (Note 4) 1.6 Single measurement method (Note 5) 0.3 Differential method (Note 4) 3 Single measurement method (Note 5) 2 C C INTERNAL ADC REFERENCE Reference Output Voltage Output Tempco VREF 2.5V mode, TA = +25C 2.470 2.500 2.530 1.0V mode, TA = +25C 0.980 1.000 1.020 TCVREF Reference Output Impedance 60 Normal operation Reference Short-Circuit Current V ppm/C 250 18 mA EXTERNAL ADC REFERENCE (INTERNAL REFERENCE DISABLED, REFERENCE APPLIED TO REF) Reference Input Voltage Range (Note 6) Input Impedance CS = GND or VDD 1 VREF = +2.5V at 50ksps (MAX1233) 5 10 VREF = +4.096V at 50ksps (MAX1234) 8 15 Input Current Shutdown/between conversions 1.0 VDD V G A 0.1 _______________________________________________________________________________________ 3 MAX1233/MAX1234 ELECTRICAL CHARACTERISTICS (continued) MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller ELECTRICAL CHARACTERISTICS (continued) (DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DIGITAL-TO-ANALOG CONVERTER DC ACCURACY Resolution 8 Bits Integral Linearity Error INL (Note 7) 1.0 LSB Differential Linearity Error DNL No missing codes 1.0 LSB Offset Error VOS (Note 8) 25 mV 1 Offset Error Temperature Coefficient 1 ppm/C Full-Scale Error Code = 255, no load 5 % Full-Scale Error Temperature Coefficient Code = 255, no load 10 ppm/C Positive and negative 0.4 V/s DYNAMIC PERFORMANCE Voltage Output Slew Rate Output Settling Time 0.5LSB; 50k and 50pF load (Note 9) 20 s Glitch Impulse Code 127 to 128 40 nV/s Wake-Up Time From shutdown 50 s DAC OUTPUT Internal DAC Reference VREFDAC Output Load Regulation Output Resistance (Note 10) 0.85 AVDD 0.9 AVDD Code = 255; 0 to 100A 0.5 Code = 0; 0 to 100A 0.5 Power-down mode 1.0 0.95 AVDD V LSB M TOUCH-SCREEN CONTROLLER On-Resistance Touch-Detection Internal Pullup Resistance Y+, X+ 7 Y-, X- 9 X+ to AVDD 1 M KEYPAD CONTROLLER Pullup Resistance C4, C3, C2, C1 (Note 11) 0.5 k Pulldown Resistance R4, R3, R2, R1 (Note 11) 16 k DIGITAL INTERFACE DIGITAL INPUTS (SCLK, CS, DIN, R_, C_) Input Voltage Low VIL Input Voltage High VIH Input Leakage Current 4 IL 0.3 DVDD 0.7 DVDD V V 0.1 _______________________________________________________________________________________ 1 A 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller (DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Input Capacitance SYMBOL CONDITIONS MIN CIN TYP MAX 15 UNITS pF DIGITAL OUTPUT (DOUT) Output Voltage Low VOL Output Voltage High VOH ISINK = 2mA 0.4 ISINK = 4mA 0.8 ISOURCE = 1.5mA DVDD 0.5 V V DIGITAL OUTPUT (BUSY, PENIRQ, KEYIRQ, R_, C_) Output Voltage Low VOL ISINK = 0.2mA Output Voltage High VOH ISOURCE = 0.2mA 0.4 DVDD 0.5 V V POWER REQUIREMENTS Supply Voltage (Note 12) Analog and Digital Supply Current AVDD / DVDD IAVDD + IDVDD MAX1233 2.7 3 3.6 MAX1234 4.75 5 5.25 Idle; all blocks shut down 0.5 5 Only ADC on; fSAMPLE = 20ksps 150 500 Only DAC on; no load 150 230 Only internal reference on 670 900 V A TIMING CHARACTERISTICS SCLK Clock Period tCP 100 ns SCLK Pulse Width High tCH 40 ns SCLK Pulse Width Low tCL 40 ns DIN to SCLK Rise Setup tDS 40 ns SCLK Rise to DIN Hold tDH 0 ns SCLK Fall to DOUT Valid tDOV CLOAD = 50pF 40 ns CS Fall to DOUT Enabled tDV CLOAD = 50pF 45 ns CS Rise to DOUT Disabled tDOD CLOAD = 50pF 40 ns CS Fall to SCLK Rise tCSS CS Fall to SCLK Ignored tCSH SCLK Rise to R_/C_ Data Valid tGPO CS Pulse Width High tCSW 40 ns 0 CLOAD = 50pF (Note 13) ns 230 40 ns ns Note 1: Tested at DVDD = AVDD = +2.7V (MAX1233), DVDD = AVDD = +5V (MAX1234). Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the offset and gain errors have been removed. Note 3: Offset nulled. Note 4: Difference between TEMP1 and TEMP2; temperature in K = (VTEMP2 - VTEMP1) x 2680K/V. No calibration is necessary. Note 5: Temperature coefficient is -2.1mV/C. Determine absolute temperature by extrapolating from a calibrated value. Note 6: ADC performance is limited by the conversion noise floor, typically 300VP-P. An external reference below 2.5V can compromise the ADC performance. Note 7: Guaranteed from code 5 to 255. _______________________________________________________________________________________ 5 MAX1233/MAX1234 ELECTRICAL CHARACTERISTICS (continued) MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller ELECTRICAL CHARACTERISTICS (continued) (DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) Note 8: Note 9: Note 10: Note 11: Note 12: Note 13: The offset value extrapolated from the range over which the INL is guaranteed. Output settling time is measured by stepping from code 5 to 255, and from code 255 to 5. Actual output voltage at full scale is 255/256 x VREFDAC. Resistance is open when configured as GPIO or in shutdown. AVDD and DVDD should not differ by more than 300mV. When configured as GPIO. Timing Diagram CS tCSW tCH tCSS tCP tCSH tCL tCSH tCSS SCLK tDH tDS DIN tDOV tDOD tDV DOUT R_/C_ NOTE: TIMING NOT TO SCALE. 6 tGPO _______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller SHUTDOWN CURRENT vs. TEMPERATURE 200 150 100 50 200 150 100 50 2.7 3.2 3.7 4.2 4.7 9.8 9.6 9.4 9.2 9.0 8.8 8.6 8.4 MAX1233/MAX1234 8.2 8.0 -40 5.2 MAX1233/34 toc03 10.0 0 0 -20 0 20 40 60 2.7 80 3.2 3.7 4.2 4.7 AVDD (V) TEMPERATURE (C) AVDD (V) INTERNAL OSCILLATOR FREQUENCY vs. TEMPERATURE TEMP1 DIODE VOLTAGE vs. ANALOG SUPPLY VOLTAGE TEMP1 DIODE VOLTAGE vs. TEMPERATURE MAX1234, AVDD = +5.0V 9.4 9.2 9.0 0.64 0.62 0.60 0.58 0.56 0.50 20 40 60 0.60 0.55 0.50 0.40 2.7 80 0.65 3.2 TEMPERATURE (C) 3.7 4.2 4.7 5.2 -40 -25 -10 5 AVDD (V) 20 35 50 65 80 TEMPERATURE (C) TEMP2 DIODE VOLTAGE vs. TEMPERATURE TEMP2 DIODE VOLTAGE vs. ANALOG SUPPLY VOLTAGE 0.75 0.70 0.65 0.90 0.85 TEMP2 DIODE VOLTAGE (V) 0.80 MAX1233/34 toc08 0 MAX1233/34 toc07 -20 TEMP2 DIODE VOLTAGE (V) -40 0.70 0.45 0.52 8.6 MAX1233/34 toc06 0.75 0.54 MAX1233, AVDD = +3.0V 8.8 0.66 5.2 0.80 TEMP1 DIODE VOLTAGE (V) 0.68 TEMP1 DIODE VOLTAGE (V) 9.6 MAX1233/34 toc05 0.70 MAX1233/34 toc04 9.8 INTERNAL OSCILLATOR FREQUENCY (MHz) MAX1233/34 toc02 250 SHUTDOWN CURRENT (nA) 250 SHUTDOWN CURRENT (nA) 300 MAX1233/34 toc01 300 INTERNAL OSCILLATOR FREQUENCY vs. ANALOG SUPPLY VOLTAGE INTERNAL OSCILLATOR FREQUENCY (MHz) SHUTDOWN CURRENT vs. ANALOG SUPPLY VOLTAGE 0.80 0.75 0.70 0.65 0.60 0.60 2.7 3.2 3.7 4.2 AVDD (V) 4.7 5.2 -40 -25 -10 5 20 35 50 65 80 TEMPERATURE (C) _______________________________________________________________________________________ 7 MAX1233/MAX1234 Typical Operating Characteristics (AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.) Typical Operating Characteristics (continued) (AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.) ADC DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE ADC INTEGRAL NONLINEARITY vs. OUTPUT CODE 0.6 0.8 0.6 0.4 0.2 0.2 DNL (LSB) 0.4 0 -0.2 MAX1233/34 toc10 0.8 INL (LSB) 1.0 MAX1233/34 toc09 1.0 0 -0.2 -0.4 -0.4 -0.6 -0.6 -0.8 -0.8 -1.0 -1.0 0 0 500 1000 1500 2000 2500 3000 3500 4000 500 1000 1500 2000 2500 3000 3500 4000 OUTPUT CODE OUTPUT CODE ADC OFFSET ERROR vs. ANALOG SUPPLY VOLTAGE ADC OFFSET ERROR vs. TEMPERATURE 1.5 OFFSET ERROR (LSB) 1.0 0.5 0 -0.5 1.0 0.5 0 -0.5 -1.0 -1.0 -1.5 -1.5 -2.0 -2.0 3.2 3.7 4.2 4.7 -40 5.2 -20 0 20 40 AVDD (V) TEMPERATURE (C) ADC GAIN ERROR vs. ANALOG SUPPLY VOLTAGE ADC GAIN ERROR vs. TEMPERATURE 1.5 0.5 0 -0.5 80 1.0 0.5 0 -0.5 -1.0 -1.0 -1.5 -1.5 -2.0 60 1.5 GAIN ERROR (LSB) 1.0 80 2.0 MAX1233/34 toc13 2.0 60 MAX1233/34 toc14 2.7 -2.0 2.7 3.2 3.7 4.2 AVDD (V) 8 MAX1233/34 toc12 1.5 OFFSET ERROR (LSB) 2.0 MAX1233/34 toc11 2.0 GAIN ERROR (LSB) MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller 4.7 5.2 -40 -20 0 20 40 TEMPERATURE (C) _______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller ADC EXTERNAL REFERENCE INPUT CURRENT vs. SAMPLING RATE ADC SUPPLY CURRENT vs. SAMPLING RATE SUPPLY CURRENT (A) 6 4 2 100 10 1 0 0.1 1k 100k 10k 1 10 100 1k 10k fSAMPLE (Hz) fSAMPLE (Hz) ADC SUPPLY CURRENT vs. SUPPLY VOLTAGE ADC SUPPLY CURRENT vs. TEMPERATURE EXTERNAL REF fSAMPLE = 20ksps 200 150 100 140 AVDD = +3V 120 SUPPLY CURRENT (A) MAX1233/34 toc17 250 100k MAX1233/34 toc18 100 SUPPLY CURRENT (A) MAX1233/34 toc16 MAX1233 VREF = +2.5V REFERENCE CURRENT (A) 1000 MAX1233/34 toc15 8 100 80 60 40 50 20 0 0 2.7 3.2 3.7 4.2 4.7 -40 5.2 0 20 40 60 80 TEMPERATURE (C) DAC INTEGRAL NONLINEARITY vs. CODE DAC DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE 0.050 MAX1233/34 toc20 0.075 MAX1233/34 toc19 0.075 0.050 0.025 0.025 DNL (LSB) INL (LSB) -20 AVDD (V) 0 -0.025 -0.050 0 -0.025 -0.500 -0.075 -0.075 -0.100 -0.100 0 50 100 150 CODE 200 250 300 0 50 100 150 200 250 300 OUTPUT CODE _______________________________________________________________________________________ 9 MAX1233/MAX1234 Typical Operating Characteristics (continued) (AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.) Typical Operating Characteristics (continued) (AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.) DAC FULL-SCALE ERROR vs. TEMPERATURE MAX1233/34 toc21 0.8 0.50 0.8 0.25 0.4 0.25 0.4 0 0 -0.4 -0.8 -0.50 -0.8 -1.2 5.5 -0.75 -0.4 -0.50 3.0 3.5 4.0 4.5 5.0 0 0 -0.25 -0.25 -1.2 -40 -20 0 20 40 60 AVDD (V) TEMPERATURE (C) DAC SUPPLY CURRENT vs. ANALOG SUPPLY VOLTAGE DAC SUPPLY CURRENT vs. TEMPERATURE 200 MAX1233/34 toc23 250 175 DAC SUPPLY CURRENT (A) 200 80 MAX1233/34 toc24 2.5 FULL-SCALE ERROR (LSB) 0.50 FULL-SCALE ERROR (%) FULL-SCALE ERROR (LSB) 1.2 0.75 -0.75 DAC SUPPLY CURRENT (A) MAX1233/34 toc22 1.2 0.75 150 100 50 FULL-SCALE ERROR (%) DAC FULL-SCALE ERROR vs. ANALOG SUPPLY VOLTAGE 150 125 100 75 50 25 0 0 3.7 4.2 4.7 5.2 -40 -20 0 20 ADC REFERENCE VOLTAGE vs. ANALOG SUPPLY VOLTAGE ADC REFERENCE VOLTAGE vs. TEMPERATURE MAX1233/34 toc25 2.525 1.020 2.60 1.010 2.55 1.000 2.500 VREF (V) VREF = 1.0V MAX1233/34 toc26 2.450 3.7 4.2 AVDD (V) 1.250 1.125 2.50 1.000 VREF = 2.5V 3.2 80 VREF = 1.0V 2.475 10 60 TEMPERATURE (C) 2.550 2.7 40 AVDD (V) 4.7 5.2 0.990 2.45 0.980 2.40 -40 VREF = 2.5V 0.875 0.750 -20 0 20 40 60 80 TEMPERATURE (C) ______________________________________________________________________________________ VREF (V) 3.2 VREF (V) 2.7 VREF (V) MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller ADC REFERENCE SUPPLY CURRENT vs. ANALOG SUPPLY VOLTAGE SUPPLY CURRENT (A) 700 650 600 MAX1233/34 toc28 750 MAX1233/34 toc27 SUPPLY CURRENT (A) 750 REFERENCE SUPPLY CURRENT vs. TEMPERATURE 700 650 600 550 550 2.7 3.2 3.7 4.2 4.7 5.2 -40 -25 -10 AVDD (V) 5 20 35 50 TEMPERATURE (C) 65 80 Pin Description PIN NAME FUNCTION 1 DVDD Positive Digital Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234. Bypass with a 0.1F capacitor. Must be within 300mV of AVDD. 2 AVDD Positive Analog Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234. Bypass with a 0.1F capacitor. Must be within 300mV of DVDD. 3* X+ X+ Position Input 4* Y+ Y+ Position Input 5* X- X- Position Input 6* Y- Y- Position Input 7 GND Analog and Digital Ground 8* BAT1 Battery Monitoring Input 1. Measures battery voltages up to 6V. 9* BAT2 Battery Monitoring Input 2. Measures battery voltages up to 6V. 10* AUX1 Auxiliary Analog Input 1 to ADC. Measures analog voltages from zero to VREF. 11* AUX2 Auxiliary Analog Input 2 to ADC. Measures analog voltages from zero to VREF. Voltage Reference Output/Input. Reference voltage for analog-to-digital conversion. In internal reference mode, the reference buffer provides a 2.5V or 1.0V nominal output. In external reference mode, apply a reference voltage between 1.0V and AVDD. Bypass REF to GND with a 0.1F capacitor in the external reference mode only. 12 REF 13 DACOUT 14 R4 Keypad Row 4. Can be reconfigured as GPIO3. 15 R3 Keypad Row 3. Can be reconfigured as GPIO2. 16 R2 Keypad Row 2. Can be reconfigured as GPIO1. 17 R1 Keypad Row 1. Can be reconfigured as GPIO0. 18 C1 Keypad Column 1. Can be reconfigured as GPIO4. DAC Voltage Output; 0.9 x AVDD Full Scale ______________________________________________________________________________________ 11 MAX1233/MAX1234 Typical Operating Characteristics (continued) (AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.) 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234 Pin Description (continued) PIN NAME 19 C2 Keypad Column 2. Can be reconfigured as GPIO5. FUNCTION 20 C3 Keypad Column 3. Can be reconfigured as GPIO6. 21 C4 Keypad Column 4. Can be reconfigured as GPIO7. 22 KEYIRQ Active-Low Keypad Interrupt. KEYIRQ is low when a key press is detected. 23 PENIRQ Active-Low Pen Touch Interrupt. PENIRQ is low when a screen touch is detected. 24 DOUT Serial Data Output. Data is clocked out at SCLK falling edge. High impedance when CS is high. 25 BUSY Active-Low Busy Output. BUSY goes low and stays low during each functional operation. The host controller should wait until BUSY is high again before using the serial interface. 26 DIN Serial Data Input. Data is clocked in on the rising edge of SCLK. Serial Clock Input. Clocks data in and out of the serial interface and sets the conversion speed (duty cycle must be 30% to 70%). 27 SCLK 28 CS Active-Low Chip Select. Data is not clocked into DIN unless CS is low. When CS is high, DOUT is high impedance. -- EP Exposed Pad. Internally connected to GND. Connect to a large ground plane to maximize thermal performance. Not intended as an electrical connection point. *ESD protected: 8kV Contact, 15kV Air. Detailed Description The MAX1233/MAX1234 are 4-wire touch-screen controllers. Figure 1 shows the functional diagram of the MAX1233/MAX1234. Each device includes a 12-bit sampling ADC, 8-bit voltage output DAC, keypad scanner that can also be configured as a GPIO, internal clock, reference, temperature sensor, two battery monitor inputs, two auxiliary analog inputs, SPI/QSPI/ MICROWIRE-compatible serial interface, and low onresistance switches for driving touch screens. The 16-bit register inside the MAX1233/MAX1234 allows for easy control and stores results that can be read at any time. The BUSY output indicates that a functional operation is in progress. The PENIRQ and KEYIRQ outputs, respectively, indicate that a screen touch or a key press has occurred. Touch-Screen Operation The 4-wire touch-screen controller works by creating a voltage gradient across the vertical or horizontal resistive touch screen connected to the analog inputs of the MAX1233/MAX1234, as shown in Figure 2. The voltage across the touch-screen panels is applied through internal MOSFET switches that connect each resistive layer to AVDD and ground. For example, to measure the Y position when a pointing device presses on the touch screen, the Y+ and Y- drivers are turned on, connecting one side of the vertical resistive layer to AVDD and the other side to ground. The horizontal resistive layer functions as a sense line. One side of this resistive layer gets connected to the X+ input, while the other side is left 12 open or floating. The point where the touch screen is pressed brings the two resistive layers in contact and creates a voltage-divider at that point. The data converter senses the voltage at the point of contact through the X+ input and digitizes it. 12-Bit ADC Analog Inputs Figure 3 shows a block diagram of the ADC's analog input section including the input multiplexer, the differential input, and the differential reference. The input multiplexer switches between X+, X-, Y+, Y-, AUX1, AUX2, BAT1, BAT2, and the internal temperature sensor. The time required for the T/H to acquire an input signal is a function of how quickly its input capacitance is charged. If the input signal's source impedance is high, the acquisition time lengthens, and more time must be allowed. The acquisition time (tACQ) is the maximum time the device takes to acquire the input signal to 12bit accuracy. Configure tACQ by writing to the ADC control register. See Table 1 for the maximum input signal source impedance (RSOURCE) for complete settling during acquisition. Accommodate higher source impedances by placing a 0.1F capacitor between the analog input and GND. Input Bandwidth The ADC's input-tracking circuitry has a 0.5MHz smallsignal bandwidth. To avoid high-frequency signals being aliased into the frequency band of interest, antialias filtering is recommended. ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller C2 C3 C4 R1 R2 R3 MAX1233/MAX1234 C1 R4 KEYPAD CONTROLLER AND GPIO OSCILLATOR MAX1233 MAX1234 REGISTERS AND SCAN STATE CONTROL TEMP SENSOR DOUT *X+ SCLK *XX/Y SWITCHES *Y+ SERIAL DATA I/O MUX 12-BIT ADC *Y- DIN CS PENIRQ KEYIRQ *BAT1 BATTERY MONITOR *BAT2 BATTERY MONITOR BUSY *AUX1 *AUX2 INTERNAL REFERENCE 2.5V/1.0V REF 8-BIT DAC DACOUT REF DAC *ESD PROTECTED Figure 1. Block Diagram Table 1. Maximum Input Source Impedance +AVDD FORCE LINE ACQUISITION RESOLUTION TIME (s) (BITS) Y+ SENSE LINE +IN +REF -IN -REF X+ SENSE LINE FORCE LINE Y- GND MAXIMUM RSOURCE FOR COMPLETE SETTLING DURING ACQUISITION (k) 1.5 8 2.6 1.5 10 2.0 1.5 12 1.5 5.0 8 23 5.0 10 19 5.0 12 15 95 8 560 95 10 470 95 12 400 Figure 2. Touch-Screen Measurement ______________________________________________________________________________________ 13 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller +AVDD TEMP2 VREF TEMP1 MAX1233 MAX1234 X+ XREF ON/OFF +REF Y+ +IN Y- CONVERTER -IN 2.5V/1.0V REFERENCE -REF 7.5k VBAT1 7.5k VBAT2 2.5k 2.5k BATTERY ON BATTERY ON AUX1 AUX2 GND Figure 3. Simplified Diagram of Analog Input Section Analog Input Protection Internal protection diodes that clamp the analog input to AVDD and GND allow the analog input pins to swing from GND - 0.3V to AV DD + 0.3V without damage. Analog inputs must not exceed AVDD by more than 50mV or be lower than GND by more than 50mV for accurate conversions. If an off-channel analog input voltage exceeds the supplies, limit the input current to 50mA. All analog inputs are also fully ESD protected 14 to 8kV, using the Contact-Discharge method and 15kV using the Air-Gap method specified in IEC1000-4-2. Reference for ADC Internal Reference The MAX1233/MAX1234 offer an internal voltage reference for the ADC that can be set to +1.0V or +2.5V. The MAX1233/MAX1234 typically use the internal reference for battery monitoring, temperature measurement, and for ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller 3R 2x REF PIN OPTIONAL 2R Figure 4. Block Diagram of the Internal Reference Full-Power Mode (RES1 = 0, RES0 = 1) In the full-power mode, the RES1 bit is set LOW and RES0 bit is set HIGH. In this mode, the device is powered up and the internal ADC reference is always ON. The MAX1233/MAX1234 internal reference remains fully powered after completing a scan. Internal Clock measurement of the auxiliary inputs. Figure 4 shows the on-chip reference circuitry of the MAX1233/MAX1234. Set the internal reference voltage by writing to the RFV bits in the ADC control register (see Tables 4, 5, and 12). The MAX1233/MAX1234 can accept an external reference connected to REF for ADC conversion. The MAX1233/MAX1234 operate from an internal oscillator, which is accurate to within 20% of the 10MHz specified clock rate. The internal oscillator controls the timing of the acquisition, conversion, touch-screen settling, reference power-up, and keypad debounce times. External Reference The MAX1233/MAX1234 can accept an external reference connected to the REF pin for ADC conversions. The internal reference should be disabled (RES1 = 1) when using an external reference. At a conversion rate of 50ksps, an external reference at REF must deliver up to 15A of load current and have 50 or less output impedance. If the external reference has high output impedance or is noisy, bypass it close to the REF pin with a 0.1F capacitor. The MAX1233/MAX1234 have a voltage-output, true 8-bit monotonic DAC with less than 1LSB integral nonlinearity error and less than 1LSB differential nonlinearity error. It requires a supply current of only 150A (typ) and provides a buffered voltage output. The DAC is at midscale code at power-up and remains there until a new code is written to the DAC register. During shutdown, the DAC's output is pulled to ground with a 1M load. Selecting Internal or External Reference Set the type of reference being used by programming the ADC control register. To select the internal reference, clock zeros into bits [A/D3:A/D0] and a zero to bit RES1, as shown in the Control Registers section. To change to external reference mode, clock zeros into bits [A/D3:A/D0] and a one to bit RES1. See Table 13 for more information about selecting an internal or external reference for the ADC. Reference Power Modes Auto Power-Down Mode (RES1 = RES0 = 0) The MAX1233/MAX1234 are in auto power-down mode at initial power-up. Set the RES1 and RES0 bits to zero to use the MAX1233/MAX1234 in the auto power-down mode. In this mode, the internal reference is normally off. When a command to perform a battery measure- 8-Bit DAC The internal DAC can be used in various system applications such as LCD/TFT-bias control, automatic tuning (VCO), power amplifier bias control, programmable threshold levels, and automatic gain control (AGC). The 8-bit DAC in the MAX1233/MAX1234 employs a current-steering topology as shown in Figure 5. At the core of this DAC is a reference voltage-to-current converter (V/I) that generates a reference current. This current is mirrored to 255 equally weighted current sources. DAC switches control the outputs of these current mirrors so that only the desired fraction of the total current-mirror currents is steered to the DAC output. The current is then converted to a voltage across a resistor, and the output amplifier buffers this voltage. DAC Output Voltage The 8-bit DAC code is binary unipolar with 1LSB = (VREF/256). The DAC has a full-scale output voltage of (0.9 x AVDD - 1LSB). ______________________________________________________________________________________ 15 MAX1233/MAX1234 +1.25V BANDGAP ment, temperature measurement, or auxiliary input measurement is written to the ADC control register, the device powers on the internal reference, waits for the internal reference to settle, completes the requested scan, and powers down the internal reference. The reference power delay depends upon the ADC resolution selected (see Table 8). Do not bypass REF with an external capacitor when performing scans in auto power-down mode. MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller +AVDD VREF 1M SW1 SW2 SW255 S1 OUT TOUCH-SCREEN DETECTOR TOUCH SCREEN PENIRQ X+ Y+ Figure 5. DAC Current-Steering Topology Output Buffer The DAC voltage output is an internally buffered unitygain follower that slews at up to 0.4V/s. The output can swing from zero to full scale. With a 1/4FS to 3/4FS output transition, the amplifier output typically settles to 1/2LSB in less than 5s when loaded with 10k in parallel with 50pF. The buffer amplifier is stable with any combination of resistive loads >10k and capacitive loads <50pF. Power-On Reset All registers of the MAX1233/MAX1234 power up at a default zero state, except the DAC data register, which is set to 10000000, so the output is at midscale. Keypad Controller and GPIO The keypad controller is designed to interface a matrixtype 4 rows x 4 columns (16 keys or fewer) keypad to a host controller. The KEY control register controls keypad interrupt, keypad scan, and keypad debounce times. The KeyMask and ColumnMask registers enable masking of a particular key or an entire column of the keypad when they are not in use. The MAX1233/MAX1234 offer two keypad data registers. KPData1 is the pending register. KPData2 holds keypad scan results of only the unmasked keys. If 12 or fewer keys are being monitored, one or more of the row/column pins of the MAX1233/MAX1234 can be software programmed as GPIO pins. Touch-Screen Detection Touch-screen detection can be enabled or disabled by writing to the ADC control register as shown in Table 4. Touch-screen detection is disabled at initial power-up. Once touch-screen detection is enabled, the Y- driver is on and the Y- pin is connected to GND. The X+ pin is internally pulled to AVDD through a 1M resistor as 16 XY- S2 Figure 6. Touch-Screen Detection Block Diagram shown in Figure 6. When the screen is touched, the X+ pin is pulled to GND through the touch screen and a touch is detected. When the 1M pullup resistor is first connected, the X+ pin can be floating near ground. To prevent false touch detection in this case, the X+ pin is precharged high for 0.1s using the 7 PMOS driver before touch detection begins. Key-Press Detection Key-press detection can be enabled or disabled by writing to the keypad control register as shown in Table 17. Key-press detection is disabled at initial power-up. Once key-press detection is enabled, the C_ pins are internally connected to DVDD and the R_ pins are internally pulled to GND through a 16k resistor. When a key is pressed, the associated row pin is pulled to DVDD and the key press is detected. Figure 7 shows the key-press detection circuitry. Interrupts PEN Interrupt Request (PENIRQ) The PENIRQ output can be used to alert the host controller of a screen touch. The PENIRQ output is normally high and goes low after a screen touch is detected. ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234 SIMPLIFIED KEYPAD CIRCUITRY DRIVERS PULL HIGH OR GO THREE-STATE C1 C2 C3 C4 R1 TO KEYPAD WAKEUP AND DEBOUNCE LOGIC KEYPAD R2 R3 R4 Figure 7. Key-Press Detection Circuitry X+ X+ PENIRQ PENIRQ BUSY BUSY CS DATA READ CS DATA READ DIN DOUT DOUT TOUCHSCREEN DATA Figure 8a. Timing Diagram for Touch-Initiated Screen Scan TOUCHSCREEN DATA Figure 8b. Timing Diagram for Host-Initiated Screen Scan ______________________________________________________________________________________ 17 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller PENIRQ returns high only after a touch-screen scan is completed. PENIRQ does not go low again until one of the touch-screen data registers is read. Figures 8a and 8b show the timing diagrams for the PENIRQ pin. Keypad Interrupt Request (KEYIRQ) The KEYIRQ output can be used to alert the host controller of a key press. The KEYIRQ output is normally high and goes low after a key press is detected. KEYIRQ returns high only after a key-press scan is completed. KEYIRQ does not go low again until one of the key-press data registers is read. Figures 9a and 9b show the timing diagrams for the KEYIRQ pin. R_ KEYIRQ BUSY CS DATA READ Busy Indicator (BUSY) BUSY informs the host processor that a scan is in progress. BUSY is normally high and goes low and stays low during each functional operation. The host controller should wait until BUSY is high again before using the serial interface. Digital Interface The MAX1233/MAX1234 interface to the host controller through a standard 3-wire serial interface at up to 10MHz. DIN and CS are the digital inputs to the MAX1233/MAX1234. DOUT is the serial data output. Data is clocked out at the SCLK falling edge and is high impedance when CS is high. When performing an ADC scan, CS must de-assert high before the end of the first conversion, otherwise the conversion results will not be stored. PENIRQ and KEYIRQ communicate interrupts from the touch-screen and keypad controllers to the host processor when a screen touch or a key press is detected. BUSY informs the host processor that a scan is in progress. In addition to these digital I/Os, the row and column pins of the keypad controller can be programmed as GPIO pins. Communications Protocol The MAX1233/MAX1234 are controlled by reading from and writing to registers through the 3-wire serial interface. These registers are addressed through a 16-bit command that is sent prior to the data. The command is shown in Table 2. The first 16 bits after the falling edge of CS contain the command word. The command word begins with an R/W bit, which specifies the direction of data flow on the serial bus. Bits 14 through 7 are reserved for future use. Bit 6 specifies the page of memory in which the DOUT TOUCHSCREEN DATA Figure 9a. Timing Diagram for Key-Press-Initiated Debounce Scan R_ KEYIRQ BUSY CS DATA READ DIN DOUT TOUCHSCREEN DATA Figure 9b. Timing Diagram for Host-Initiated Keypad Debounce Scan desired register is located. The last 6 bits specify the address of the desired register. The next 16 bits of data are read from or written to the address specified in the command word. After 32 clock cycles, the interface automatically increments its address pointer and continues reading or writing until the rising edge of CS, or until it reaches the end of the page. Table 2. Command Word Format BIT15 MSB BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 LSB R/W RES RES RES RES RES RES RES RES PAGE ADD5 ADD4 ADD3 ADD2 ADD1 ADD0 18 ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller WRITE READ COMMAND COMMAND (HEX) (HEX) REGISTER NAME BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 X0 -- 0x8000 X 0 0 0 0 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 -- 0x8001 Y 0 0 0 0 Y11 Y10 Y9 Y8 Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 -- 0x8002 Z1 0 0 0 0 Z1_11 Z1_10 Z1_9 Z1_8 Z1_7 Z1_6 Z1_5 Z1_4 Z1_3 Z1_2 Z1_1 Z1_0 -- 0x8003 Z2 0 0 0 0 Z2_11 Z2_10 Z2_9 Z2_8 Z2_7 Z2_6 Z2_5 Z2_4 Z2_3 Z2_2 Z2_1 Z2_0 -- 0x8004 KPD K15 K14 K13 K12 K11 K10 K9 K8 K7 K6 K5 K4 K3 K2 K1 K0 -- 0x8005 BAT1 0 0 0 0 B1_11 B1_10 B1_9 B1_8 B1_7 B1_6 B1_5 B1_4 B1_3 B1_2 B1_1 B1_0 -- 0x8006 BAT2 0 0 0 0 B2_11 B2_10 B2_9 B2_8 B2_7 B2_6 B2_5 B2_4 B2_3 B2_2 B2_1 B2_0 -- 0x8007 AUX1 0 0 0 0 A1_11 A1_10 A1_9 A1_8 A1_7 A1_6 A1_5 A1_4 A1_3 A1_2 A1_1 A1_0 -- 0x8008 AUX2 0 0 0 0 A2_11 A2_10 A2_9 A2_8 A2_7 A2_6 A2_5 A2_4 A2_3 A2_2 A2_1 A2_0 -- 0x8009 TEMP1 0 0 0 0 T1_11 T1_10 T1_9 T1_8 T1_7 T1_6 T1_5 T1_4 T1_3 T1_2 T1_1 T1_0 -- 0x800A TEMP2 0 0 0 0 T2_11 T2_10 T2_9 T2_8 T2_7 T2_6 T2_5 T2_4 T2_3 T2_2 T2_1 T2_0 0x000B 0x800B DAC data 0 0 0 0 0 0 0 0 DA7 DA6 DA5 DA4 DA3 DA2 DA1 DA0 0x000F 0x800F GPIO data GPD7 GPD6 GPD5 GPD4 GPD3 GPD2 GPD1 GPD0 0 0 0 0 0 0 0 0 -- 0x8010 KPData1 K1_15 K1_14 K1_13 K1_12 K1_11 K1_10 K1_9 K1_8 K1_7 K1_6 K1_5 K1_4 K1_3 K1_2 K1_1 K1_0 -- 0x8011 KPData2 K2_15 K2_14 K2_13 K2_12 K2_11 K2_10 K2_9 K2_8 K2_7 K2_6 K2_5 K2_4 K2_3 K2_2 K2_1 K2_0 0x0040 0x8040 ADC control PENSTS ADSTS A/D3 A/D2 A/D1 A/D0 RES1 RES0 AVG1 AVG0 CNR1 CNR0 ST2 ST1 ST0 RFV 0x0041 0x8041 KEY control KEYSTS1 KEYSTS0 DBN2 DBN1 DBN0 HLD2 HLD1 HLD0 0 0 0 0 0 0 0 0 0x0042 0x8042 DAC control 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0x004E 0x804E GPIO pullup PU7 PU6 PU5 PU4 PU3 PU2 PU1 PU0 0 0 0 0 0 0 0 0 0x004F 0x804F GPIO control GP7 GP6 GP5 GP4 GP3 GP2 GP1 GP0 OE7 OE6 OE5 OE4 OE3 OE2 OE1 OE0 DAPD 0 0x0050 0x8050 KPKeyMask KM15 KM14 KM13 KM12 KM11 KM10 KM9 KM8 KM7 KM6 KM5 KM4 KM3 KM2 KM1 KM0 0x0051 0x8051 KPColumnMask CM4 CM3 CM2 CM1 0 0 0 0 0 0 0 0 0 0 0 0 Note: All other registers are reserved and should always be 0. Power-on reset state is DAC data at midscale (0x0080), all other registers are 0. ______________________________________________________________________________________ 19 MAX1233/MAX1234 Table 3. Register Summary MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller In order to read the entire first page of memory, for example, the host processor must send the MAX1233/MAX1234 the command 0x8000 H . The MAX1233/MAX1234 then begin clocking out 16-bit data starting with the X-data register. In order to write to the second page of memory, the host processor sends the MAX1233/MAX1234 the command 0x0040H. The succeeding data is then written in 16-bit words beginning with the ADC control register. Figures 10a and 10b show a complete write and read operation, respectively, between the processor and the MAX1233/MAX1234. Memory Map The MAX1233/MAX1234s' internal memory is divided into two pages--one for data and one for control, each of which contains thirty-two 16-bit registers. Control Registers Table 3 provides a summary of all registers and bit locations of the MAX1233/MAX1234. ADC Control Register The ADC measures touch position, touch pressure, battery voltage, auxiliary analog inputs, and temperature. The ADC control register determines which input is selected and converted. Tables 4 and 5 show the format and bit descriptions for the ADC control register. SCLK WRITE OPERATION CS D0 D15 DIN D15 IS READ/WRITE BIT LOW FOR WRITE DOUT D0 D15 D15-D0 COMMAND WORD D15-D0 DATA WORD THREESTATE THREESTATE TIMING NOT TO SCALE. Figure 10a. Timing Diagram of Write Operation SCLK READ OPERATION CS D15 D14 DIN D0 D15-D0 COMMAND WORD DOUT THREE-STATE D0 D15 D15 DATA WORD D0 THREE-STATE DATA WORD Figure 10b. Timing Diagram of Read Operation Table 4. ADC Control Register (Write 0x0040/Read 0x8040) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 PENSTS ADSTS A/D3 RES1 RES0 AVG1 AVG0 CNR1 CNR0 ST2 ST1 ST0 RFV 20 A/D2 A/D1 A/D0 ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Bits 6-7: Converter Averaging Control These bits specify the number of data averages the converter performs. Table 9 shows how to program for the desired number of averages. When averaging is used, ADSTS and BUSY indicate the converter is busy until all conversions needed for the averaging finish. These bits are identical, regardless of read or write. Bits 10-13: ADC Scan Select These bits control which input to convert and which converter mode is used. The bits are identical regardless of a read or write. See Table 7 for details about using these bits. Bits 4-5: ADC Conversion Rate Control These bits specify the internal conversion rate, which the ADC uses to perform a single conversion, as shown in Table 10. Lowering the conversion rate also reduces power consumption. These bits are identical, regardless of read or write. Bits 8-9: ADC Resolution Control These bits specify the ADC resolution and are identical regardless of read or write. Table 8 shows how to use these bits to set the resolution. Table 5. ADC Control Register Bit Descriptions (Write 0x0040/Read 0x8040) BIT NAME 15 (MSB) PENSTS DESCRIPTION 14 ADSTS 13 A/D3 Selects ADC scan functions 12 A/D2 Selects ADC scan functions 11 A/D1 Selects ADC scan functions 10 A/D0 Selects ADC scan functions 9 RES1 Controls ADC resolution Read: pen interrupt status; Write: sets interrupt initiated touch-screen scans Read: ADC status; Write: stops ADC 8 RES0 Controls ADC resolution 7 AVG1 Controls ADC result averaging 6 AVG0 Controls ADC result averaging 5 CNR1 Controls ADC conversion rate 4 CNR0 3 ST2 Controls touch-screen settling wait time 2 ST1 Controls touch-screen settling wait time 1 ST0 Controls touch-screen settling wait time 0 (LSB) RFV Chooses 1.0V or 2.5V reference Controls ADC conversion rate Table 6. ADSTS Bit Operation PENSTS ADSTS READ FUNCTION WRITE FUNCTION 0 0 No screen touch detected; scan or conversion in progress Performs one scan and waits to detect a screen touch. Upon detection, issues an interrupt and waits until told to scan by the host controller. 1 0 Screen touch detected; scan or conversion in progress Stops any ongoing scan and waits to detect a screen touch. Upon detection, issues an interrupt and performs a scan. 0 1 No screen touch detected; data available Stops any ongoing scan and waits to detect a screen touch. Upon detection, issues an interrupt and waits until told to scan by the host controller. 1 1 Screen touch detected; data available Stops any ongoing scan and powers down the screen touch detection circuit. No screen touches are detected in this mode. ______________________________________________________________________________________ 21 MAX1233/MAX1234 Bits 14-15: Pen Interrupt Status and ADC Status Bits These bits are used to control or monitor ADC scans. MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Table 7. ADC Scan Select (Touch Screen, Battery, Auxiliary Channels, and Temperature) A/D3 A/D2 A/D1 A/D0 FUNCTION 0 0 0 0 Configures the ADC reference as selected by RES [1:0] bits as shown in Table 13. No measurement is performed. 0 0 0 1 Measures X/Y touch position and returns results to the X and Y data registers. 0 0 1 0 Measures X/Y touch position and Z1/ Z2 touch pressure and returns results to the X, Y, Z1, and Z2 data registers. 0 0 1 1 Measures X touch position and returns results to the X data register. 0 1 0 0 Measures Y touch position and returns results to the Y data register. 0 1 0 1 Measures Z1/Z2 touch pressure and returns results to the Z1 and Z2 data register. 0 1 1 0 Measures Battery Input 1 through a 4:1 divider and returns results to the BAT1 data register. 0 1 1 1 Measures Battery Input 2 through a 4:1 divider and returns results to the BAT2 data register. 1 0 0 0 Measures Auxiliary Input 1 and returns results to the AUX1 data register. 1 0 0 1 Measures Auxiliary Input 2 and returns results to the AUX2 data register. 1 0 1 0 Measures temperature (single ended) and returns results to the TEMP1 data register. 1 0 1 1 Measures Battery Input 1, Battery Input 2, Auxiliary Input 1, Auxiliary Input 2, and temperature (differential), and returns results to the appropriate data registers. 1 1 0 0 Measures temperature (differential) and returns results to the TEMP1 and TEMP2 data registers. 1 1 0 1 Turns on Y+, Y- drivers. No measurement is performed. 1 1 1 0 Turns on X+, X- drivers. No measurement is performed. 1 1 1 1 Turns on Y+, X- drivers. No measurement is performed. Table 8. ADC Resolution Control RES1 RES0 ADC RESOLUTION INTERNALLY TIMED REFERENCE POWER-UP DELAY* (s) 0 0 8 bit 31 0 1 8 bit 31 1 0 10 bit 37 1 1 12 bit 44 *Applicable only for temperature, battery, or auxiliary measurements in auto power-up reference mode. Table 10. ADC Conversion Rate Control CNR1 CNR0 FUNCTION 0 0 3.5s/sample (1.5s acquisition, 2s conversion) 0 1 3.5s/sample (1.5s acquisition, 2s conversion) 1 0 10s/sample (5s acquisition, 5s conversion) 1 1 100s/sample (95s acquisition, 5s conversion) Table 9. ADC Averaging Control AVG1 AVG0 FUNCTION 0 0 No data averages (default) 0 1 4 data averages 1 0 8 data averages 1 1 16 data averages 22 ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Internal ADC Reference Power-Down Control The ADC control register controls the power setting of the internal ADC reference. Zeros must be written to bits A/D3-A/D0 to control internal reference power-up followed by the appropriate logic at the RES1 and RES0 bits. Table 13 shows the internal ADC reference powerdown control. Bit 0: ADC Internal Reference Voltage Control This bit selects the ADC internal reference voltage, either +1.0V or +2.5V. This bit is identical, regardless of read or write. The reference control bit is shown in Table 12. DAC Control Register The MSB in this control register determines the powerdown control of the on-board DAC. Table 14 shows the DAC control register. Writing a zero to bit 15 (DAPD) powers up the DAC, while writing a 1 powers down the DAC. Table 15 describes the DAC control register contents, while Table 16 shows the DAC power-down bit. Table 11. Touch-Screen Settling Time Control* Keypad Control Registers The keypad control register, keypad mask register, and keypad column mask control register control the keypad scanner in the MAX1233/MAX1234. The keypad control register (Table 17) controls scanning and debouncing, while the keypad mask register (Table 22) and the keypad column mask control register (Table 24), ST2 ST1 ST0 0 0 0 Settling time: 0s SETTLING TIME 0 0 1 Settling time: 100s 0 1 0 Settling time: 500s 0 1 1 Settling time: 1ms 1 0 0 Settling time: 5ms 1 0 1 Settling time: 10ms 1 1 0 Settling time: 50ms BIT NAME DESCRIPTION 1 1 1 Settling time: 100ms 15 (MSB) DAPD DAC powered down [14:0] 0 Reserved Table 15. DAC Control Register Descriptions *Applicable only for X, Y, Z1, and Z2 measurements. Table 12. ADC Reference Control Bit Table 16. DAC Power-Down Bit DAPC FUNCTION 0 +1.0V reference 0 DAC powered up 1 +2.5V reference 1 DAC powered down RFV FUNCTION Table 13. Internal ADC Reference Auto Power-Up Control [A/D3:A/D0] RES1 RES0 ADC REFERENCE SOURCE 0000 0 0 Internal ADC REFERENCE POWER MODE Power up, wait for reference to settle, and power down again for each temperature, battery, or auxiliary scan (auto power-up mode) 0000 0 1 Internal Always powered up 0000 1 0 External Always powered down 0000 1 1 External Always powered down Table 14. DAC Control Register (Write 0x0042/Read 0x8042) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 DAPD 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ______________________________________________________________________________________ 23 MAX1233/MAX1234 Bits 1-3: Touch-Screen Settling Time Control These bits specify the time delay from pen-touch detection to a conversion start. This allows the selection of the appropriate settling time for the touch screen being used. Table 11 shows how to set the settling time. These bits are identical, regardless of read or write. MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Table 17. Keypad Control Register (Write 0x0041/Read 0x8041) BIT15 BIT14 KEYSTS1 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 KEYSTS0 DBN2 DBN1 DBN0 HLD2 HLD HLD 0 0 0 0 0 0 0 0 Table 18. Keypad Control Register Bit Descriptions (Write 0x0041/Read 0x8041) BIT NAME 15 (MSB) KEYSTS1 Read: keypad interrupt status; Write: set interrupt initiated keypad scans DESCRIPTION 14 KEYSTS0 Read: keypad scan status; Write: stop keypad scan 13 DBN2 Keypad debounce time control 12 DBN1 Keypad debounce time control 11 DBN0 Keypad debounce time control 10 HLD2 Keypad hold time control 9 HLD1 Keypad hold time control 8 HLD0 [7:0] 0 Keypad hold time control Reserved Table 19. KEYSTS1/KEYSTS0 Functions KEYSTS1 KEYSTS0 READ FUNCTION WRITE FUNCTION 0 0 No button press detected; scan or debounce in progress Scans keypad once and waits to detect a button press. Upon detection, issues an interrupt and waits for the host's instruction before scanning. 1 0 Button press detected; scan or debounce in progress Stops any ongoing scan and waits to detect a button press. Upon detection, issues an interrupt and scans the keypad. 0 1 No button press detected; data available Stops any ongoing scan and waits to detect a button press. Upon detection, issues an interrupt and waits for the host's instruction before scanning. 1 1 Button press detected; data available Stops any ongoing scan and powers down the button press detection circuit. No button presses are detected in this mode. Table 20. Keypad Debounce Time Control DBN2 DBN1 DBN0 0 0 0 Debounce time: 2 0 0 1 Debounce time: 10 0 1 0 Debounce time: 20 0 1 1 Debounce time: 50 1 0 0 Debounce time: 60 1 0 1 Debounce time: 80 1 1 0 Debounce time: 100 1 1 1 Debounce time: 120 24 FUNCTION (ms) ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller GPIO Control Register The GPIO control register and the GPIO pullup register allow the keypad controller's row and column inputs to be configured as up to eight parallel I/O pins. Tables 26 and 27 show the GPIO control register layout and control register descriptions. Tables 28 and 29 show the GPIO pullup disable register and associated descriptions. For more information, see the Applications Information section. Table 21. Keypad Hold Time Control HLD2 HLD1 HLD0 0 0 0 If a button is held, wait 100s before beginning next debounce scan FUNCTION 0 0 1 If a button is held, wait 1 debounce time before beginning the next debounce scan 0 1 0 If a button is held, wait 2 debounce times before beginning the next debounce scan 0 1 1 If a button is held, wait 3 debounce times before beginning the next debounce scan 1 0 0 If a button is held, wait 4 debounce times before beginning the next debounce scan 1 0 1 If a button is held, wait 5 debounce times before beginning the next debounce scan 1 1 0 If a button is held, wait 6 debounce times before beginning the next debounce scan 1 1 1 If a button is held, wait 7 debounce times before beginning the next debounce scan Table 22. Keypad Key Mask Register Bit Descriptions (Write 0x0050/Read 0x8050) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 KM15 KM14 KM13 KM12 KM11 KM10 KM9 KM8 KM7 KM6 KM5 KM4 KM3 KM2 KM1 KM0 Table 23. Keypad Key Mask Register Bit Descriptions (Write 0x0050/Read 0x8050) BIT NAME DESCRIPTION 15 KM15 Mask status register data update on individual key for row 4, column 4 14 KM14 Mask status register data update on individual key for row 3, column 4 13 KM13 Mask status register data update on individual key for row 2, column 4 12 KM12 Mask status register data update on individual key for row 1, column 4 11 KM11 Mask status register data update on individual key for row 4, column 3 10 KM10 Mask status register data update on individual key for row 3, column 3 9 KM9 Mask status register data update on individual key for row 2, column 3 8 KM8 Mask status register data update on individual key for row 1, column 3 7 KM7 Mask status register data update on individual key for row 4, column 2 6 KM6 Mask status register data update on individual key for row 3, column 2 5 KM5 Mask status register data update on individual key for row 2, column 2 4 KM4 Mask status register data update on individual key for row 1, column 2 3 KM3 Mask status register data update on individual key for row 4, column 1 2 KM2 Mask status register data update on individual key for row 3, column 1 1 KM1 Mask status register data update on individual key for row 2, column 1 0 KM0 Mask status register data update on individual key for row 1, column 1 Table 24. Keypad Column Mask Register (Write 0x0051/Read 0x8051) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 CM4 CM3 CM2 CM1 0 0 0 0 0 0 0 0 0 0 0 0 ______________________________________________________________________________________ 25 MAX1233/MAX1234 allowing certain keys to be masked from detection. Tables 18-21 show the programmable bits of the keypad control register. Tables 23, 24, and 25 show the programmable bits of the keypad mask registers. The Keypad Controller and GPIO section provides more details. MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Table 25. Keypad Column Mask Register Bit Descriptions (Write 0x0051/Read 0x8051) BIT NAME 15 CM4 Mask interrupt, status register, and pending register data update on all keys in column 4 DESCRIPTION 14 CM3 Mask interrupt, status register, and pending register data update on all keys in column 3 13 CM2 Mask interrupt, status register, and pending register data update on all keys in column 2 12 CM1 Mask interrupt, status register, and pending register data update on all keys in column 1 [11:0] 0 Reserved Table 26. GPIO Control Register (Write 0x004F/Read 0x804F) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 GP7 GP6 GP5 GP4 GP3 GP2 GP1 GP0 OE7 OE6 OE5 OE4 OE3 OE2 OE1 OE0 Table 27. GPIO Control Register Bit Descriptions (Write 0x004F/Read 0x804F) DESCRIPTION BIT NAME 15 GP7 C4 pin becomes GPIO pin 7 C4 pin remains keypad column 4 14 GP6 C3 pin becomes GPIO pin 6 C3 pin remains keypad column 3 13 GP5 C2 pin becomes GPIO pin 5 C2 pin remains keypad column 2 12 GP4 C1 pin becomes GPIO pin 4 C1 pin remains keypad column 1 11 GP3 R4 pin becomes GPIO pin 3 R4 pin remains keypad row 4 10 GP2 R3 pin becomes GPIO pin 2 R3 pin remains keypad row 3 9 GP1 R2 pin becomes GPIO pin 1 R2 pin remains keypad row 2 8 GP0 R1 pin becomes GPIO pin 0 R1 pin remains keypad row 1 [7:0] [OE7:OE0] GPIO pin configured as an output GPIO pin configured as an input 1 0 Table 28.GPIO Pullup Disable Register (Write 0x004E/Read 0x804E) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 PU7 PU6 PU5 PU4 PU3 PU2 PU1 PU0 0 0 0 0 0 0 0 0 Table 29. GPIO Pullup Disable Register Descriptions BIT NAME DESCRIPTION [15:8] [PU7:PU0] 1: Pullup disabled. Open collector output. 0: Pullup enabled. [7:0] 0 Reserved: always write as zero. Data Registers The data results from conversions or keypad scans are held in the data registers of the MAX1233/MAX1234. During power-up, all of these data registers with the exception of the DAC data register default to 0000H. The DAC register defaults to 1000H. 26 Analog Input Data Registers Table 30 shows the format of the X, Y, Z1, Z2, BAT1, BAT2, AUX1, AUX2, TEMP1, and TEMP2 data registers. The data format for these registers is right justified beginning with bit 11. Data written through the serial interface to these registers is not stored. Keypad Data Registers Table 31 shows the formatting of the keypad data registers, while Tables 32, 33, and 34 provide individual register bit descriptions. These registers have the same format as the keypad mask register. Each bit represents one key on the keypad. Table 35 shows a map of a 16-key keypad. Data written through the serial interface to these registers is not stored. ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller READ REGISTER BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 COMMAND NAME 0x8000 X 0 0 0 0 0x8001 Y 0 0 0 0x8002 Z1 0 0 0 0x8003 Z1 0 0 0x8005 BATT1 0 0x8006 BATT2 0 0x8007 AUX1 0x8008 AUX2 0x8009 0x800A BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 X0 0 Y11 Y10 Y9 Y8 Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 0 Z1_11 Z1_10 Z1_9 Z1_8 Z1_7 Z1_6 Z1_5 Z1_4 Z1_3 Z1_2 Z1_1 Z1_0 0 0 Z2_11 Z2_10 Z2_9 Z2_8 Z2_7 Z2_6 Z2_5 Z2_4 Z2_3 Z2_2 Z2_1 Z2_0 0 0 0 B1_11 B1_10 B1_9 B1_8 B1_7 B1_6 B1_5 B1_4 B1_3 B1_2 B1_1 B1_0 0 0 0 B2_11 B2_10 B2_9 B2_8 B2_7 B2_6 B2_5 B2_4 B2_3 B2_2 B2_1 B2_0 0 0 0 0 A1_11 A1_10 A1_9 A1_8 A1_7 A1_6 A1_5 A1_4 A1_3 A1_2 A1_1 A1_0 0 0 0 0 A2_11 A2_10 A2_9 A2_8 A2_7 A2_6 A2_5 A2_4 A2_3 A2_2 A2_1 A2_0 TEMP1 0 0 0 0 T1_11 T1_10 T1_9 T1_8 T1_7 T1_6 T1_5 T1_4 T1_3 T1_2 T1_1 T1_0 TEMP2 0 0 0 0 T2_11 T2_10 T2_9 T2_8 T2_7 T2_6 T2_5 T2_4 T2_3 T2_2 T2_1 T2_0 Table 31. Keypad Data Registers READ REGISTER BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 COMMAND NAME 0x8004 KPD K15 K14 K13 K12 K11 K10 K9 K8 K7 K6 K5 K4 K3 K2 K1 K0 0x8010 KPData1 (column K1_15 K1_14 K1_13 K1_12 K1_11 K1_10 K1_9 K1_8 K1_7 K1_6 K1_5 K1_4 K1_3 K1_2 K1_1 K1_0 maskable) 0x8011 KPData2 (key K2_15 K2_14 K2_13 K2_12 K2_11 K2_10 K2_9 K2_8 K2_7 K2_6 K2_5 K2_4 K2_3 K2_2 K2_1 K2_0 maskable) Table 32. Keypad Data Register Descriptions BIT NAME DESCRIPTION 15 K15 Keypad scan result for row 4, column 4. Can only be masked by column mask. 14 K14 Keypad scan result for row 3, column 4. Can only be masked by column mask. 13 K13 Keypad scan result for row 2, column 4. Can only be masked by column mask. 12 K12 Keypad scan result for row 1, column 4. Can only be masked by column mask. 11 K11 Keypad scan result for row 4, column 3. Can only be masked by column mask. 10 K10 Keypad scan result for row 3, column 3. Can only be masked by column mask. 9 K9 Keypad scan result for row 2, column 3. Can only be masked by column mask. 8 K8 Keypad scan result for row 1, column 3. Can only be masked by column mask. 7 K7 Keypad scan result for row 4, column 2. Can only be masked by column mask. 6 K6 Keypad scan result for row 3, column 2. Can only be masked by column mask. 5 K5 Keypad scan result for row 2, column 2. Can only be masked by column mask. 4 K4 Keypad scan result for row 1, column 2. Can only be masked by column mask. 3 K3 Keypad scan result for row 4, column 1. Can only be masked by column mask. 2 K2 Keypad scan result for row 3, column 1. Can only be masked by column mask. 1 K1 Keypad scan result for row 2, column 1. Can only be masked by column mask. 0 K0 Keypad scan result for row 1, column 1. Can only be masked by column mask. ______________________________________________________________________________________ 27 MAX1233/MAX1234 Table 30. Analog Inputs Data Register Format MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Table 33. Keypad Data Register 1 (Pending Register) Descriptions BIT NAME 15 K1_15 Keypad scan result for row 4, column 4. Can only be masked by column mask. DESCRIPTION 14 K1_14 Keypad scan result for row 3, column 4. Can only be masked by column mask. 13 K1_13 Keypad scan result for row 2, column 4. Can only be masked by column mask. 12 K1_12 Keypad scan result for row 1, column 4. Can only be masked by column mask. 11 K1_11 Keypad scan result for row 4, column 3. Can only be masked by column mask. 10 K1_10 Keypad scan result for row 3, column 3. Can only be masked by column mask. 9 K1_9 Keypad scan result for row 2, column 3. Can only be masked by column mask. 8 K1_8 Keypad scan result for row 1, column 3. Can only be masked by column mask. 7 K1_7 Keypad scan result for row 4, column 2. Can only be masked by column mask. 6 K1_6 Keypad scan result for row 3, column 2. Can only be masked by column mask. 5 K1_5 Keypad scan result for row 2, column 2. Can only be masked by column mask. 4 K1_4 Keypad scan result for row 1, column 2. Can only be masked by column mask. 3 K1_3 Keypad scan result for row 4, column 1. Can only be masked by column mask. 2 K1_2 Keypad scan result for row 3, column 1. Can only be masked by column mask. 1 K1_1 Keypad scan result for row 2, column 1. Can only be masked by column mask. 0 K1_0 Keypad scan result for row 1, column 1. Can only be masked by column mask. Table 34. Keypad Data Register 2 (Status Register) Descriptions 28 BIT NAME 15 K2_15 Keypad scan result for row 4, column 4. Can be masked by key mask or column mask. DESCRIPTION 14 K2_14 Keypad scan result for row 3, column 4. Can be masked by key mask or column mask. 13 K2_13 Keypad scan result for row 2, column 4. Can be masked by key mask or column mask. 12 K2_12 Keypad scan result for row 1, column 4. Can be masked by key mask or column mask. 11 K2_11 Keypad scan result for row 4, column 3. Can be masked by key mask or column mask. 10 K2_10 Keypad scan result for row 3, column 3. Can be masked by key mask or column mask. 9 K2_9 Keypad scan result for row 2, column 3. Can be masked by key mask or column mask. 8 K2_8 Keypad scan result for row 1, column 3. Can be masked by key mask or column mask. 7 K2_7 Keypad scan result for row 4, column 2. Can be masked by key mask or column mask. 6 K2_6 Keypad scan result for row 3, column 2. Can be masked by key mask or column mask. 5 K2_5 Keypad scan result for row 2, column 2. Can be masked by key mask or column mask. 4 K2_4 Keypad scan result for row 1, column 2. Can be masked by key mask or column mask. 3 K2_3 Keypad scan result for row 4, column 1. Can be masked by key mask or column mask. 2 K2_2 Keypad scan result for row 3, column 1. Can be masked by key mask or column mask. 1 K2_1 Keypad scan result for row 2, column 1. Can be masked by key mask or column mask. 0 K2_0 Keypad scan result for row 1, column 1. Can be masked by key mask or column mask. ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller GPIO Data Register Tables 37 and 38 show the format and descriptions for the GPIO data register. The register is left justified with data in bit 15-bit 8. Reading the GPIO data register gives the state of the R_ and C_ pins. Data written to the GPIO data register appears on those R_ and C_ pins, which are configured as general-purpose outputs. Data written to pins not configured as general-purpose outputs is not stored. ADC Transfer Function Applications Information Programmable 8-/10-/12-Bit Resolution The MAX1233/MAX1234 provide the option of three different resolutions for the ADC: 8, 10, or 12 bits. Lower resolutions are practical for some measurements such as touch pressure. Lower resolution conversions have smaller conversion times and therefore consume less power. Program the resolution of the MAX1233/ MAX1234 12-bit ADCs by writing to the RES1 and RES0 bits in the ADC control register. When the MAX1233/ MAX1234 power up, both bits are set to zero so the resolution is set to 8 bits with a 31s internally timed reference power-up delay as indicated by the ADC resolution control table. As explained in the control register section, the RES1 and RES0 bits control the refer- The MAX1233/MAX1234 output data is in straight binary format as shown in Figure 11. This figure shows the ideal output code for the given input voltage and does not include the effects of offset error, gain error, noise, or nonlinearity. OUTPUT CODE MAX1233 MAX1234 FULL-SCALE TRANSITION 11 ... 111 11 ... 110 11 ... 101 Table 35. Keypad to Key Bit Mapping COMPONENT FS = VREF C1 C2 C3 C4 R1 K0 K4 K8 K12 00 ... 011 R2 K1 K5 K9 K13 00 ... 010 R3 K2 K6 K10 K14 00 ... 001 R4 K3 K7 K11 K15 00 ... 000 ZS = GND 1LSB = VREF 4096 0 1 2 3 INPUT VOLTAGE (LSB) FS FS - 3/2LSB Figure 11. Ideal Input Voltages and Output Codes Table 36. DAC Data Register(Write 0x000B/Read 0x800B) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 0 0 0 0 0 0 0 0 DA7 DA6 DA5 DA4 DA3 DA2 DA1 DA0 Table 37. GPIO Data Register (Write 0x000F/Read 0x800F) BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0 GPD7 GPD6 GPD5 GPD4 GPD3 GPD2 GPD1 GPD0 0 0 0 0 0 0 0 0 Table 38. GPIO Data Register Bit Descriptions (Write 0x000F/Read 0x800F) BIT NAME 15...8 GPD7...0 7...0 0 DESCRIPTION GPIO data bits for GPIO pins 7...0 Reserved ______________________________________________________________________________________ 29 MAX1233/MAX1234 DAC Data Register The DAC data register stores data that is to be written to the 8-bit DAC. Table 36 shows the configuration of the DAC data register. It is right justified with bit 7-bit 0 storing the input data. MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller +AVDD FORCE LINE Y+ SENSE LINE X+ +REF CONVERTER -IN -REF +IN SENSE LINE FORCE LINE Touch-Pressure Measurement Y- GND Figure 12. Ratiometric Y-Coordinate Measurement ence power-up status when the A/D0-A/D3 bits are zero. These values can be set initially on power-up. (Subsequently A/D0-A/D3 bits are not zero, and any other value of these bits is exclusive to ADC resolution programming.) Differential Ratiometric Touch-Position Measurement The MAX1233/MAX1234 provide differential conversions. Figure 12 shows the switching matrix configuration for Y coordinate measurement. The +REF and -REF inputs are connected directly to Y+ and Y-. The conversion result is a percentage of the external resistances, and is unaffected by variation in the total touch-screen resistance or the on-resistance of the internal switching matrix. The touch screen remains powered during the acquisition and conversion process. Touch-Screen Settling There are two mechanisms that affect the voltage level at the point where the touch panel is pressed. One is electrical ringing due to parasitic capacitance between the top and bottom layers of the touch screen and the other is the mechanical bouncing caused by vibration of the top layer of the touch screen. Thus, the input sig- 30 nal, reference, or both may not settle into their final steady-state values before the ADC samples the inputs, and the reference voltage may continue to change during the conversion cycle. The MAX1233/MAX1234 can be programmed to wait for a fixed amount of time after a screen touch has been detected before beginning a scan. Use the touch-screen settling control bits in the ADC control register (Table 11) to set the settling delay to between zero and 100ms. The settling problem is amplified in some applications where external filter capacitors may be required across the touch screen to filter noise that may be generated by the LCD panel or backlight circuitry, etc. The values of these capacitors cause an additional settling time requirement when the panel is touched. Any failure to settle before conversion start may show up as a gain error. Average the conversion result by writing to the ADC control register, as shown in Table 10, to minimize noise. The MAX1233/MAX1234 provide two methods of measurement of the pressure applied to the touch screen. Although 8-bit resolution is typically sufficient, the following calculations use 12-bit resolution demonstrating the maximum precision of the MAX1233/MAX1234. Figure 13 shows the pressure measurement block diagram. The first method performs pressure measurements using a known X-plate resistance. After completing three conversions, X-position, Z1-position, and Z2 position, use the following equation to calculate RTOUCH : X Z RTOUCH = RXPLATE x POSITION x 2 - 1 4096 Z1 ( ) The second method requires knowing both the X-plate and Y-plate resistance. Three touch-screen conversions are required in this method as well for measurement of the X-position, Y-position, and Z- position of the touch screen. Use the following equation to calculate RTOUCH: X 4096 R RTOUCH = XPLATE x POSITION x - 1 Z1 4096 Z1 Y - RYPLATE x POSITION 4096 ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller SENSE LINE X+ MEASURE X-POSITION HOST WRITES ADC CONTROL REGISTER Y+ MAX1233/MAX1234 FORCE LINE BATTERY INPUT 1 OR BATTERY INPUT 2 TOUCH START CLOCK V X-POSITION XFORCE LINE MEASURE Z1-RESISTANCE SET BUSY LOW YOPEN CIRCUIT SENSE LINE FORCE LINE X+ Y+ NO IS ADC REFERENCE IN AUTO POWER-DOWN MODE? TOUCH V YES Z1-RESISTANCE POWER UP REFERENCE X- YOPEN CIRCUIT FORCE LINE POWER UP ADC FORCE LINE OPEN CIRCUIT X+ POWER DOWN ADC Y+ CONVERT BATTERY INPUT 1 OR 2 TOUCH POWER DOWN REFERENCE V Z2-RESISTANCE SET BUSY HIGH FORCE LINE X- Y- SENSE LINE MEASURE Z2-RESISTANCE NO IS DATA AVERAGING DONE? TURN OFF CLOCK Figure 13. Pressure Measurement Block Diagram YES DC/DC CONVERTER BATTERY 0.5V TO 6.0V DONE 2.7V STORE BATTERY INPUT 1 OR 2 IN BAT1 OR BAT2 REGISTER AVDD VBAT 7.5k Figure 15. Battery Voltage-Reading Flowchart Battery-Voltage Monitors 0.125V TO 1.5V CONVERTER 2.5k Figure 14. Battery Measurement Block Diagram Two dedicated analog inputs (BAT1 and BAT2) allow the MAX1233/MAX1234 to monitor the battery voltages prior to the DC/DC converter. Figure 14 shows the battery voltage monitoring circuitry. The MAX1233/ MAX1234 directly monitor battery voltages from 0.5V to 6V. An internal resistor network divides down BAT1 and BAT2 by 4 so that a 6V battery voltage results in a 1.5V input to the ADC. To minimize power consumption, the divider is only enabled during the sampling of BAT1 and BAT2. Figure 15 illustrates the process of battery input reading. ______________________________________________________________________________________ 31 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Auxiliary Analog Inputs Two auxiliary analog inputs (AUX1 and AUX2) allow the MAX1233/MAX1234 to monitor analog input voltages from zero to VREF. Figure 16 illustrates the process of auxiliary input reading. HOST WRITES ADC CONTROL REGISTER START CLOCK Temperature Measurements The MAX1233/MAX1234 provide two temperature measurement options: a single-ended conversion method and a differential conversion method. Both temperature measurement techniques rely on the semiconductor junction's operational characteristics at a fixed current level. The forward diode voltage (VBE) vs. temperature is a well-defined characteristic. The ambient temperature can be predicted in applications by knowing the value of the VBE voltage at a fixed temperature and then monitoring the delta of that voltage as the temperature changes. Figure 17 illustrates the functional block of the internal temperature sensor. The single conversion method requires calibration at a known temperature, but only requires a single reading to predict the ambient temperature. First, the internal diode forward bias voltage is measured by the ADC at a known temperature. Subsequent diode measurements provide an estimate of the ambient temperature through extrapolation. This assumes a temperature coefficient of -2.1mV/C. The single conversion method results in a resolution of 0.29C/LSB (2.5V reference) and 0.12C/LSB (1.0V reference) with a typical accuracy of 2C. Figure 18 shows the flowchart for the single temperature measurement. The differential conversion method uses two measurement points. The first measurement is performed with a fixed bias current into the internal diode. The second measurement is performed with a fixed multiple of the original bias current. The voltage difference between the first and second conversion is proportional to the absolute temperature and is expressed by the following formula: VBE = (kT/q) ln(N) SET BUSY LOW NO IS ADC REFERENCE IN AUTO POWER-DOWN MODE? YES POWER UP REFERENCE POWER UP ADC POWER DOWN ADC CONVERT AUXILIARY INPUT 1 OR 2 POWER DOWN REFERENCE SET BUSY HIGH NO IS DATA AVERAGING DONE? TURN OFF CLOCK YES DONE STORE AUXILIARY INPUT 1 OR 2 IN AUX1 OR AUX2 REGISTER Figure 16. Auxiliary Input Flowchart where: VBE = difference in diode voltage N = current ratio of the second measurement to the first measurement k = Boltzmann's constant (1.38 x 10-23 eV/Kelvin) q = electron charge (1.60 x 10-19 C) T = temperature in Kelvin The resultant equation solving for K is: T(K) = q x V / (k x ln(N)) AUXILIARY INPUT 1 OR AUXILIARY INPUT 2 MUX TEMP1 A/D CONVERTER TEMP2 Figure 17. Internal Block Diagram of Temperature Sensor 32 ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller NO HOST WRITES ADC CONTROL REGISTER TEMPERATURE INPUT 1 START CLOCK START CLOCK SET BUSY LOW SET BUSY LOW IS ADC REFERENCE IN AUTO POWER-DOWN MODE? NO YES YES POWER UP REFERENCE POWER UP ADC CONVERT TEMPERATURE INPUT 1 IS ADC REFERENCE IN AUTO POWER-DOWN MODE? POWER UP REFERENCE POWER UP ADC POWER DOWN ADC CONVERT TEMPERATURE INPUT 1 POWER DOWN REFERENCE SET BUSY HIGH NO IS DATA AVERAGING DONE? YES TEMPERATURE INPUT 1 AND TEMPERATURE INPUT 2 CONVERT TEMPERATURE INPUT 2 NO IS DATA AVERAGING DONE? YES STORE TEMPERATURE INPUT 2 IN TEMP2 REGISTER POWER DOWN ADC POWER DOWN REFERENCE SET BUSY HIGH NO TURN OFF CLOCK MAX1233/MAX1234 HOST WRITES ADC CONTROL REGISTER IS DATA AVERAGING DONE? TURN OFF CLOCK YES DONE STORE TEMPERATURE INPUT 1 IN TEMP1 REGISTER DONE STORE TEMPERATURE INPUT 1 IN TEMP1 REGISTER Figure 18. Single Temperature Measurement Process Figure 19. Differential Temperature Measurement Process where: V = V (I N) - V (I1) (in mV) is 1.6C/LSB (2.5V reference) and 0.65C/LSB (1V reference) with a typical accuracy of 3C. Figure 19 shows the differential temperature measurementprocess. T(K) = 2.68(K/mV) x V(mV) T(C) = [2.68(K/mV) x V(mV) - 273K]C/ K This differential conversion method does not require a test temperature calibration and can provide much improved absolute temperature measurement. In the differential conversion method, however, the resolution Note: The bias current for each diode temperature measurement is only turned ON during the acquisition and, therefore, does not noticeably increase power consumption. ______________________________________________________________________________________ 33 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Battery Voltage, Auxiliary Input, and Temperature Input Scan Use this scan to make periodic measurements of both battery inputs, both auxiliary inputs, and both temperature inputs. The respective data registers have the latest results at the end of each cycle. Thus, a single write by the host to the MAX1233/MAX1234 ADC control register results in six different measurements being made. Figure 20 shows this scan operation. Touch-Initiated Screen Scans (PENSTS = 1; ADSTS = 0) In the touch-initiated screen-scan mode, the MAX1233/MAX1234 automatically perform a touchscreen scan upon detecting a screen touch. The touchscreen scans performed are determined by the [A/D3:A/D0] written to the ADC control register. Figure 21 shows the flowchart for a complete touch-initiated Xand Y- coordinate scan. Selection of resolution, conversion rate, averaging, and touch-screen settling time determine the overall conversion time. Figure 22 shows the complete flowchart for a touchinitiated X, Y, and Z scan. Table 38 shows ADSTS Bit Operation. Host-Initiated Screen Scans (PENSTS = ADSTS = 0) In this mode, the host processor decides when a touchscreen scan begins. The MAX1233/MAX1234 detect a screen touch and drive PENIRQ LOW. The host recognizes the interrupt request and can choose to write to the ADC control register to select a touch-screen scan function (PENSTS = ADSTS = 0). Figures 23 and 24 show the process of a host-initiated screen scan. Key-Press Initiated Debounce Scan (KEYSTS1 = 1, KEYSTS0 =0) In the key-press initiated debounce mode, the MAX1233/MAX1234 automatically perform a debounce upon detecting a key press. Key scanning begins once a key press has been detected and ends when a key press has been debounced (Figures 25 and 9a). Host-Initiated Debounce Scan In this mode, the host processor decides when a debounce scan begins. The MAX1233/MAX1234 detect a key press and drive KEYIRQ low. The host processor recognizes the interrupt request and can choose to write to the keypad control register to initiate a debounce scan (Figures 26 and 9b). Keypad Debouncing Keys are debounced either when (1) a key press has been detected, or (2) when commanded by the host MPU. 34 The keys scanned by the keypad row and column pins are debounced for a period of time (debounce period) as determined by bits [DBN2:DBN0] of the keypad control register. The keypad controller continues scanning until the keypad stays in the same state for an entire debounce period. Keypad Data Keypad data can be read out of either the keypad data status register (maskable), or the keypad data pending register (not maskable). The keypad mask register is used to mask individual keys in the keypad data status register. GPIO Control Write to bits [GP7:GP0] of the GPIO control register to configure one or more of the R_/C_pins as a GPIO pin. Write to bits [OE7:OE0] of the GPIO control register to configure the pins as an input or an output. GPIO data can be read from or written to the GPIO data register. A read returns the logic state of the GPIO pin. A write sets the logic state of a GPIO output pin. Writing to a GPIO input pin has no effect. GPIO Pullup Disable Register When programmed as GPIO output, by default, the GPIO pins are active CMOS outputs. Write a 1 to the pullup disable register to configure the GPIO output as an open-drain output. Using the 8-Bit DAC for LCD/TFT Contrast Control Design Example: The 8-bit DAC offers the ability to control biasing of LCD/TFT screens. In the circuit of Figure 27, it is desired to have the MAX1677 DC-DC converter's VOUT to be adjustable. The minimum and maximum DAC voltages (VDAC(HIGH) and V DAC(LOW) ) can be found in the Electrical Characteristics table. The output voltage of the MAX1677 (VOUT) can be calculated by noting the following equations: VOUT = VREFDAC + i1R1 [Equation 1] i1 = i2 + i3 [Equation 2] i2 = VREFDAC / R2 [Equation 3] [Equation 4] i3 = (VREFDAC - VDAC) / R3 Substituting equations 2, 3, and 4 into equation 1 yields: VOUT = VREFDAC + (R1 / R2) VREF + (R1 / R3) [Equation 5] (VREFDAC - VDAC) ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234 BATTERY VOLTAGE, AUXILIARY INPUT, AND TEMPERATURE INPUT SCAN ([A/D3:A/D0] = 1011) HOST WRITES ADC CONTROL REGISTER CONVERT BATTERY INPUT 2 CONVERT TEMPERATURE INPUT 1 START CLOCK SET BUSY LOW NO NO IS DATA AVERAGING DONE? NO YES IS ADC REFERENCE IN AUTO POWER-DOWN MODE? STORE BATTERY INPUT 2 IN BAT2 REGISTER IS DATA AVERAGING DONE? YES STORE TEMPERATURE INPUT 1 IN TEMP1 REGISTER YES CONVERT AUXILIARY INPUT 1 POWER UP REFERENCE POWER UP ADC NO CONVERT BATTERY INPUT 1 NO IS DATA AVERAGING DONE? YES IS DATA AVERAGING DONE? CONVERT TEMPERATURE INPUT 2 NO IS DATA AVERAGING DONE? YES STORE AUXILIARY INPUT 1 IN AUX1 REGISTER STORE TEMPERATURE INPUT 2 IN TEMP2 REGISTER CONVERT AUXILIARY INPUT 2 POWER DOWN ADC YES POWER DOWN REFERENCE STORE BATTERY INPUT 1 IN BAT1 REGISTER NO IS DATA AVERAGING DONE? YES SET BUSY HIGH TURN OFF CLOCK DONE STORE AUXILIARY INPUT 2 IN AUX2 REGISTER Figure 20. Scan Mode Flowchart ______________________________________________________________________________________ 35 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller PENIRQ-INITIATED X- AND Y- SCREEN SCAN SCREEN TOUCH YES POWER DOWN ADC TURN ON DRIVERS: X+. X- ARE THERE UNREAD SCAN RESULTS? NO NO SET PENIRQ LOW IS TOUCH-SCREEN SETTLING DONE? YES IS PENSTS BIT = 1? POWER UP ADC GO TO NO HOST-INITIATED SCAN (FIGURE 23) CONVERT Y- COORDINATES YES START CLOCK NO IS DATA AVERAGING DONE? SET BUSY LOW YES TURN ON DRIVERS: Y+, Y- NO IS TOUCH-SCREEN SETTLING DONE? STORE Y- COORDINATES IN Y- REGISTER POWER DOWN ADC SET BUSY HIGH YES POWER UP ADC CONVERT X- COORDINATES TURN OFF CLOCK RESET PENIRQ HIGH DONE NO IS DATA AVERAGING DONE? YES STORE X- COORDINATES IN X- REGISTER Figure 21. Touch-Initiated X- and Y- Coordinate Screen Scan 36 ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234 PENIRQ-INITIATED X, Y, AND Z SCREEN SCAN SCREEN TOUCH STORE X- COORDINATES IN X- REGISTER YES ARE THERE UNREAD SCAN RESULTS? CONVERT Z1- COORDINATES POWER DOWN ADC NO TURN ON DRIVERS: X+, X- NO YES SET PENIRQ LOW NO IS PENSTS BIT = 1? IS DATA AVERAGING DONE? GO TO HOST-INITIATED SCAN (FIGURE 24) STORE Z1- COORDINATES IN Z1- REGISTER IS TOUCH-SCREEN SETTLING DONE? CONVERT Z2 COORDINATES YES POWER UP ADC YES NO START CLOCK IS DATA AVERAGING DONE? CONVERT Y- COORDINATES YES SET BUSY LOW NO IS DATA AVERAGING DONE? STORE Z2- COORDINATES IN Z2- REGISTER TURN ON DRIVERS: Y+, Y- YES NO POWER UP ADC STORE Y- COORDINATES IN Y- REGISTER IS TOUCH-SCREEN SETTLING DONE? SET BUSY HIGH POWER DOWN ADC YES TURN OFF CLOCK POWER UP ADC TURN ON DRIVERS: Y+, XRESET PENIRQ HIGH CONVERT X- COORDINATES NO NO IS DATA AVERAGING DONE? IS TOUCH-SCREEN SETTLING DONE? DONE YES POWER UP ADC Figure 22. Touch-Initiated X- , Y-, and Z- Coordinate Screen Scan ______________________________________________________________________________________ 37 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller HOST-INITIATED X- AND Y- SCREEN SCAN SCREEN TOUCH STORE X- COORDINATES IN X- REGISTER POWER DOWN ADC YES ARE THERE UNREAD SCAN RESULTS? TURN ON DRIVERS: X+, XNO SET PENIRQ LOW NO IS PENSTS BIT = 1? YES GO TO TOUCH-INITIATED SCAN (FIGURE 21) IS TOUCH-SCREEN SETTLING DONE? YES POWER UP ADC NO HOST WRITES ADC CONTROL REGISTER (PENSTS = ADSTS = 0) SET BUSY LOW START CLOCK CONVERT Y- COORDINATES NO IS DATA AVERAGING DONE? YES STORE Y- COORDINATES IN Y- REGISTER TURN ON DRIVERS: Y+, YPOWER DOWN ADC NO IS TOUCH-SCREEN SETTLING DONE? YES SET BUSY HIGH TURN OFF CLOCK POWER UP ADC RESET PENIRQ HIGH CONVERT X- COORDINATES DONE NO IS DATA AVERAGING DONE? YES Figure 23. Host-Initiated X- and Y- Coordinate Screen Scan 38 ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234 HOST-INITIATED X-, Y-, AND Z- SCREEN SCAN TURN ON DRIVERS: Y+, XSCREEN TOUCH NO YES ARE THERE UNREAD SCAN RESULTS? TURN ON DRIVERS: X+, X- YES POWER UP ADC NO SET PENIRQ LOW IS PENSTS BIT = 1? IS TOUCH-SCREEN SETTLING DONE? NO YES GO TO TOUCH-INITIATED SCAN (FIGURE 22) IS TOUCH-SCREEN SETTLING DONE? CONVERT Z1- COORDINATES YES POWER UP ADC NO IS DATA AVERAGING DONE? NO HOST WRITES ADC CONTROL REGISTER START CLOCK YES CONVERT Y- COORDINATES STORE Z1- COORDINATES IN Z1- REGISTER NO IS DATA AVERAGING DONE? CONVERT Z2- COORDINATES SET BUSY LOW YES TURN ON DRIVERS: Y+, Y- STORE Y- COORDINATES IN Y- REGISTER POWER DOWN ADC NO IS TOUCH-SCREEN SETTLING DONE? YES NO IS DATA AVERAGING DONE? YES STORE Z2- COORDINATES IIN Z2- REGISTER POWER DOWN ADC POWER UP ADC SET BUSY HIGH CONVERT X- COORDINATES TURN OFF CLOCK NO IS DATA AVERAGING DONE? YES RESET PENIRQ HIGH STORE X- COORDINATES IN X- REGISTER DONE POWER DOWN ADC Figure 24. Host-Initiated X-, Y-, and Z- Coordinate Screen Scan ______________________________________________________________________________________ 39 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller HOST-INITIATED DEBOUNCE SCAN KEY-PRESS-INITIATED DEBOUNCE SCAN KEYPAD TOUCH KEYPAD TOUCH YES YES ARE THERE UNREAD DEBOUNCE RESULTS? ARE THERE UNREAD DEBOUNCE RESULTS? NO SET KEYIRQ LOW NO SET KEYIRQ LOW IS KEYSTS1 = 1? IS KEYSTS1 = 1? NO GO TO HOST-INITIATED DEBOUNCE SCAN YES YES GO TO KEY-PRESS-INITIATED DEBOUNCE SCAN NO HOST WRITES ADC CONTROL REGISTER START CLOCK START CLOCK SET BUSY LOW SET BUSY LOW SCAN AND DEBOUNCE KEYS SCAN AND DEBOUNCE KEYS STORE KEYPAD SCAN RESULTS IN REGISTER STORE KEYPAD SCAN RESULTS IN REGISTER SET BUSY HIGH SET BUSY HIGH RESET KEYIRQ HIGH RESET KEYIRQ HIGH DONE DONE Figure 25. Key-Press-Initiated Debounce Scan 40 Figure 26. Host-Initiated Debounce Scan ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234 VBATT MAX1233 MAX1234 FEEDBACK RESISTORS SIMPLIFIED DC/DC CONVERTER AVDD DACOUT R1 i1 R2 i2 ERROR AMP R3 DAC i3 CONTROL VREF 1.25V VOUT (LCD BIAS) MAX1677 Figure 27. LCD Contrast Control Circuit CS CS SCLK SCK SCLK MISO DOUT MISO DOUT SPI VDD CS CS SCK MOSI DIN MAX1233 MAX1234 MICROWIRE MOSI DIN BUSY BUSY PENIRQ PENIRQ KEYIRQ KEYIRQ MAX1233 MAX1234 SS Figure 28a. SPI Interface Figure 28b. MICROWIRE Interface Equation 5 shows that the maximum output voltage occurs for the minimum DAC voltage, and that the minimum output voltage occurs for the maximum DAC voltage. To ensure that the desired output swing is achieved, choose appropriate values of R1, R2, and R3. Calculate VOUTMIN using the following equation: VOUTMIN= VREFMIN + (R1MIN / R2MAX)VREFMIN + (R1MAX / R3MIN) (VREFMIN - VDACMAX) [Equation 7] If VOUTMIN is too low for desired operation, avoid the DAC codes, which cause the output voltage to go too low. Calculate VOUTMAX using the following equation: VOUTMAX = VREFMAX + (R1MAX / R2MIN)VREFMAX + (R1MAX / R3MIN) (VREFMAX - VDACMIN) [Equation 6] If V OUTMAX exceeds the maximum ratings of the LCD/TFT display, the DAC codes that cause the output voltage to go too high must be avoided. Connection to Standard Interface SPI and MICROWIRE Interfaces When using an SPI interface (Figure 28a) or MICROWIRE (Figure 28b), set the CPOL = CPHA = 0. At least four 8-bit operations are necessary to read or write data to/from the MAX1233/MAX1234. DOUT data transitions on the serial clock's falling edge and is clocked into the P on the SCLK's rising edge. The first ______________________________________________________________________________________ 41 MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller CS CS SCK SCLK MISO DOUT QSPI VDD MOSI MAX1233 MAX1234 DIN BUSY PENIRQ KEYIRQ SS Figure 29. QSPI Interface SUPPLIES +3V/+5V GND +3V/+5V R* = 10 AVDD GND MAX1233 MAX1234 DVDD VDD DGND DIGITAL CIRCUITRY connections. Establish a single-point analog ground (star ground point) at GND. Connect all analog grounds to the star ground. Connect the digital system ground to the star ground at this point only. For lowest noise operation, the ground return to the star ground's power supply should be low impedance and as short as possible. High-frequency noise in the power supply may affect the high-speed comparator in the ADC. Bypass the supply to the star ground with a 0.1F capacitor as close to pins 1 and 2 of the MAX1233/MAX1234 as possible. Minimize capacitor lead lengths for best supply-noise rejection. If the power supply is very noisy, a 10 resistor can be connected as a lowpass filter. While using the MAX1233/MAX1234 with a resistive touch screen, the interconnection between the converter and the touch screen should be as short and robust as possible. Since resistive touch screens have a low resistance, longer or loose connections are a source of error. Noise can also be a major source of error in touch-screen applications (e.g., applications that require a backlight LCD panel). This EMI noise can be coupled through the LCD panel to the touch screen and cause "flickering" of the converted data. Utilizing a touch screen with a bottom-side metal layer connected to ground couples the majority of noise to ground. In addition, the filter capacitors from Y+, Y-, X+, and Xinputs to ground also help reduce the noise further. Caution should be observed for settling time of the touch screen. Definitions *OPTIONAL Figure 30. Power-Supply Grounding Connection two 8-bit data streams write the command word into the MAX1233/MAX1234. The next two 8-bit data streams can contain either the input or output data. QSPI Interface Using the high-speed QSPI interface (Figure 29) with CPOL = 0 and CPHA = 0, the MAX1233/MAX1234 support a maximum fSCLK of 10MHz. DOUT data transitions on the serial clock's falling edge and is clocked into the P on the SCLK's rising edge. Layout, Grounding, and Bypassing For best performance, use printed circuit boards with good layouts; do not use wire-wrap boards even for prototyping. Ensure that digital and analog signal lines are separated from each other. Do not run analog and digital (especially clock) lines parallel to one another, or digital lines underneath the ADC package. Figure 30 shows the recommended system ground 42 Integral Nonlinearity Integral nonlinearity (INL) is the deviation of the values on an actual transfer function from a straight line. This straight line can be either a best-straight-line fit or a line drawn between the end points of the transfer function, once offset and gain errors have been nullified. The static linearity parameters for the MAX1233/MAX1234 are measured using the end-point method. Differential Nonlinearity Differential nonlinearity (DNL) is the difference between an actual step width and the ideal value of 1LSB. A DNL error specification of less than 1LSB guarantees no missing codes and a monotonic transfer function. Aperture Jitter Aperture jitter (tAJ) is the sample-to-sample variation in the time between the samples. Aperture Delay Aperture delay (tAD) is the time defined between the falling edge of the sampling clock and the instant when an actual sample is taken. ______________________________________________________________________________________ 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the RMS sum of the first five harmonics of the input signal to the fundamental itself. This is expressed as: Signal-to-Noise Plus Distortion Signal-to-noise plus distortion (SINAD) is the ratio of the fundamental input frequency's RMS amplitude to the RMS equivalent of all other ADC output signals: SINAD (dB) = 20 log (SignalRMS / NoiseRMS) Effective Number of Bits Effective number of bits (ENOB) indicates the global accuracy of an ADC at a specific input frequency and sampling rate. An ideal ADC's error consists of quantization noise only. With an input range equal to the full-scale range of the ADC, calculate the effective number of bits as follows: ENOB = (SINAD - 1.76) / 6.02 V 2 + V32 + V4 2 + V52 THD = 20 x log 2 V12 where V1 is the fundamental amplitude, and V2 through V5 are the amplitudes of the 2nd- through 5th-order harmonics, respectively. Spurious-Free Dynamic Range Spurious-free dynamic range (SFDR) is the ratio of RMS amplitude of the fundamental (maximum signal component) to the RMS value of the next-largest distortion component. Chip Information TRANSISTOR COUNT: 28,629 Package Information For the latest package outline information, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 28 QFN G2855-2 21-0091 28 TQFN T2855-6 21-0140 ______________________________________________________________________________________ 43 MAX1233/MAX1234 Signal-to-Noise Ratio For a waveform perfectly reconstructed from digital samples, signal-to-noise ratio (SNR) is the ratio of full-scale analog input (RMS value) to the RMS quantization error (residual error). The ideal, theoretical minimum analogto-digital noise is caused by quantization error only and results directly from the ADC's resolution (N bits): SNR = (6.02 N + 1.76) dB In reality, there are other noise sources besides quantization noise: thermal noise, reference noise, clock jitter, etc. SNR is computed by taking the ratio of the RMS signal to the RMS noise, which includes all spectral components minus the fundamental, the first five harmonics, and the DC offset. MAX1233/MAX1234 15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller Revision History REVISION NUMBER REVISION DATE 0 7/02 Initial release 4 3/08 Added register address information. Fixed DCLK typo. Fixed CS timing dependency. DESCRIPTION PAGES CHANGED -- 12, 18-27, 29, 41, 42 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 44 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products.