EVAL-AD7843EBZ Analog Devices

Touch Screen Digitizer AD7843 FEATURES FUNCTIONAL BLOCK DIAGRAM 4-wire touch screen interface +V PENIRQ CC Specified throughput rate of 125 kSPS Low power consumption: PEN 1.37 mW max at 125 kSPS with VCC = 3.6 V AD7843 INTERRUPT X+ Single supply, VCC of 2.2 V to 5.25 V X Ratiometric conversion High speed serial interface Y+ T/H Programmable 8-bit or 12-bit resolution Y 4-TO-1 2 auxiliary analog inputs I/P MUX Shutdown mode: 1 A max IN3 COMP 16-lead QSOP and TSSOP packages IN4 V GND REF APPLICATIONS CHARGE Personal digital assistants REDISTRIBUTION DAC Smart hand-held devices +V CC Touch screen monitors SAR + ADC Point-of-sales terminals CONTROL LOGIC Pagers SPORT DIN CS DOUT DCLK BUSY Figure 1. GENERAL DESCRIPTION PRODUCT HIGHLIGHTS The AD7843 is a 12-bit successive approximation ADC with a 1. Ratiometric conversion mode available eliminating errors synchronous serial interface and low on resistance switches for due to on-board switch resistances. driving touch screens. The part operates from a single 2.2 V to 2. Maximum current consumption of 380 A while operating 5.25 V power supply and features throughput rates greater than at 125 kSPS. 125 kSPS. 3. Power-down options available. 4. Analog input range from 0 V to V . REF The external reference applied to the AD7843 can be varied 5. Versatile serial I/O port. from 1 V to +VCC, while the analog input range is from 0 V to V The device includes a shutdown mode that reduces the REF. current consumption to less than 1 A. The AD7843 features on-board switches. This, coupled with low power and high speed operation, make this device ideal for battery-powered systems such as personal digital assistants with resistive touch screens, and other portable equipment. The part is available in a 16-lead 0.15 quarter size outline package (QSOP) and a 16-lead thin shrink small outline package (TSSOP). Rev. B 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 rights of third parties that may result from its use. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Specifications subject to change without notice. No license is granted by implication Tel: 781.329.4700 www.analog.com or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Fax: 781.326.8703 2004 Analog Devices, Inc. All rights reserved. 02144-B-001AD7843 TABLE OF CONTENTS Specifications..................................................................................... 3 Analog Input ............................................................................... 12 Timing Specifications .................................................................. 4 Control Register ......................................................................... 14 Absolute Maximum Ratings............................................................ 5 Power vs. Throughput Rate....................................................... 15 ESD Caution.................................................................................. 5 Serial Interface ............................................................................ 16 Pin Configuration and Function Descriptions............................. 6 Detailed Serial Interface Timing .............................................. 17 Terminology ...................................................................................... 7 Pen Interrupt Request................................................................ 19 Typical Performance Characteristics ............................................. 8 Grounding and Layout .............................................................. 19 Circuit Information........................................................................ 11 Outline Dimensions ....................................................................... 20 ADC Transfer Function............................................................. 11 Ordering Guide .......................................................................... 20 Typical Connection Diagram ................................................... 11 REVISION HISTORY 3/04Data Sheet Changed from Rev. A to Rev. B Updated Format..................................................................Universal Changes to Absolute Maximum Ratings ....................................... 5 Addition to the PD0 and PD1 Section......................................... 14 Additions to Ordering Guide........................................................ 20 3/03Data Sheet Changed from Rev. 0 to Rev. A Updated Outline Dimensions ....................................................... 16 Rev. B Page 2 of 20