Touch Screen Digitizer Data Sheet AD7873 FEATURES FUNCTIONAL BLOCK DIAGRAM +V CC PENIRQ 4-wire touch screen interface On-chip temperature sensor: 40C to +85C On-chip 2.5 V reference PEN Direct battery measurement (0 V to 6 V) TEMP INTERRUPT X+ SENSOR Touch pressure measurement X Specified throughput rate of 125 kSPS AD7873 Y+ Single supply, VCC of 2.2 V to 5.25 V T/H Y Ratiometric conversion 6-TO-1 High speed serial interface I/P MUX Programmable 8-bit or 12-bit resolution AUX One auxiliary analog input COMP BATTERY Shutdown mode: 1 A maximum MONITOR 16-lead QSOP, TSSOP, and LFCSP packages V BAT APPLICATIONS V REF Personal digital assistants GND Smart hand-held devices CHARGE Touch screen monitors REDISTRIBUTION +V DAC CC 2.5V Point-of-sale terminals BUF REF Pagers SAR + ADC GENERAL DESCRIPTION CONTROL LOGIC The AD7873 is a 12-bit successive approximation ADC with a synchronous serial interface and low on resistance switches for SPORT driving touch screens. The AD7873 operates from a single 2.2 V to 5.25 V supply, with a throughput rate of 125 kSPS. The AD7873 features direct battery measurement, temperature DIN CS DOUT DCLK BUSY measurement, and touch pressure measurement. The AD7873 Figure 1. also has an on-board reference of 2.5 V that can be used for the PRODUCT HIGHLIGHTS auxiliary input, battery monitor, and temperature measurement 1. Ratiometric conversion mode available, eliminating errors modes. When not in use, the internal reference can be shut due to on-board switch resistances. down to conserve power. An external reference can also be applied and varied from 1 V to VCC with an analog input range 2. On-board temperature sensor: 40C to +85C. from 0 V to VREF. The device includes a shutdown mode that 3. Battery monitor input. reduces the current consumption to less than 1 A. 4. Touch pressure measurement capability. The AD7873 features on-board switches. This, coupled with low 5. Low power consumption of 1.37 mW maximum with the power and high speed operation, makes the device ideal for reference off, or 2.41 mW typical with the reference on, at battery-powered systems with resistive touch screens. The part 125 kSPS and VCC at 3.6 V. is available in a 16-lead, 0.15 inch quarter size outline package 6. Package options include 4 mm 4 mm LFCSP. (QSOP), a 16-lead, thin shrink small outline package (TSSOP), 7. Analog input range from 0 V to V . and a 16-lead, lead frame chip scale package (LFCSP). REF 8. Versatile serial I/O ports. Rev. F Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. 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Trademarks and registered trademarks are the property of their respective owners. 02164-001AD7873 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Circuit Information ........................................................................ 13 Applications ....................................................................................... 1 ADC Transfer Function ............................................................. 13 General Description ......................................................................... 1 Typical Connection Diagram ................................................... 13 Functional Block Diagram .............................................................. 1 Analog Input ............................................................................... 14 Product Highlights ........................................................................... 1 Measurements ............................................................................. 16 Revision History ............................................................................... 2 Pen Interrupt Request ................................................................ 18 Specif icat ions ..................................................................................... 3 Control Register ......................................................................... 19 Timing Specifications .................................................................. 5 Power vs. Throughput Rate ....................................................... 20 Absolute Maximum Ratings ............................................................ 6 Serial Interface ............................................................................ 21 Thermal Resistance ...................................................................... 6 Grounding and Layout .................................................................. 23 ESD Caution .................................................................................. 6 PCB Design Guidelines for Chip Scale Package .................... 23 Pin Configurations and Function Descriptions ........................... 7 Outline Dimensions ....................................................................... 24 Terminology ...................................................................................... 8 Ordering Guide .......................................................................... 25 Typical Performance Characteristics ............................................. 9 REVISION HISTORY 2/13Rev. E to Rev. F 4/03Rev. B to Rev. C Changes to General Description Section ...................................... 1 Changes to Formatting ...................................................... Universal Added EPAD Note to Figure 3 and Table 5 ................................... 7 Updated Outline Dimensions ....................................................... 19 Updated Outline Dimensions ....................................................... 24 1/02Rev. A to Rev. B Changes to Ordering Guide .......................................................... 26 Addition of 16-Lead Lead Frame Chip Scale Package .. Universal 9/06Rev. D to Rev. E Edits to Features ................................................................................. 1 Changes to Figure 13 Caption ...................................................... 10 Edits to General Description ........................................................... 1 Updated Outline Dimensions ....................................................... 24 Addition of LFCSP Pin Configuration ........................................... 4 Changes to Ordering Guide .......................................................... 25 Edit to Absolute Maximum Ratings ................................................ 4 Addition to Ordering Guide ............................................................ 4 6/04Rev. C to Rev. D Addition of CP-16 Outline Dimensions .................................... 19 Updated Format .................................................................. Universal Changes to Absolute Maximum Ratings ....................................... 6 2/01Rev. 0 to Rev A Additions to PD0 and PD1 Description ...................................... 21 Edits to Notes in the Ordering Guide PBC Guidelines for Chip Scale Package Added ......................... 23 Additions to Ordering Guide ........................................................ 25 Rev. F Page 2 of 28