Low Voltage Controller for Touch Screens Data Sheet AD7879/AD7889 FEATURES FUNCTIONAL BLOCK DIAGRAM V /REF CC 4-wire touch screen interface 1.6 V to 3.6 V operation X Y X+ Y+ Median and averaging filter to reduce noise Automatic conversion sequencer and timer X+ X User-programmable conversion parameters REF REF REF+ Auxiliary analog input/battery monitor (0.5 V to 5 V) Y+ 1 optional GPIO Y Interrupt outputs (INT, PENIRQ) 12-BIT RESULT GND SAR ADC Touch-pressure measurement REGISTERS TEMPERATURE Wake-up on touch function SENSOR Shutdown mode: 6 A maximum AD7879/ 12-ball, 1.6 mm 2 mm WLCSP AD7879-1 CONTROL REGISTERS AD7889/ 16-lead, 4 mm 4 mm LFCSP AD7889-1 APPLICATIONS Personal digital assistants SEQUENCER SERIAL PORT AND TIMER Smart handheld devices TO RESULT Touch screen monitors REGISTERS Point-of-sale terminals CS/ DIN/ DOUT/ SCL Medical devices ADD0 ADD1 SDA Cell phones Figure 1. GENERAL DESCRIPTION The AD7879/AD7889 are 12-bit successive approximation The AD7879/AD7889 have a programmable pin that can analog-to-digital converters (SAR ADCs) with a synchronous operate as an auxiliary input to the ADCs, as a battery monitor, serial interface and low on-resistance switches for driving 4-wire or as a general-purpose input/output (GPIO). In addition, a resistive touch screens. The AD7879/AD7889 work with a very programmable interrupt output can operate in three modes: as a general-purpose interrupt to signal when new data is available low power supplya single 1.6 V to 3.6 V supplyand feature a throughput rate of 105 kSPS. The devices include a shutdown (DAV), as an interrupt to indicate when limits are exceeded mode that reduces current consumption to less than 6 A. (INT), or as a pen-down interrupt when the screen is touched (PENIRQ). The AD7879/AD7889 offer temperature To reduce the effects of noise from LCDs and other sources, the measurement and touch pressure measurement. AD7879/AD7889 contain a preprocessing block. The preprocessing function consists of a median filter and an The AD7879 is available in a 12-ball, 1.6 mm 2 mm WLCSP averaging filter. The combination of these two filters provides a and in a 16-lead, 4 mm 4 mm LFCSP. The AD7889 is available more robust solution, discarding the spurious noise in the signal in a backside coated version of the WLCSP. Both devices support 2 and keeping only the data of interest. The size of both filters is an SPI interface (AD7879/AD7889) or an I C interface (AD7879-1/ programmable. Other user-programmable conversion controls AD7889-1). include variable acquisition time and first conversion delay up Note that throughout this data sheet, multifunction pins, such to 16 averages can be taken per conversion. The AD7879/AD7889 as PENIRQ/INT/DAV, are referred to either by the entire pin can run in slave mode or standalone (master) mode, using an name or by a single function of the pin, for example, , PENIRQ automatic conversion sequencer and timer. when only that function is relevant. Rev. D Document Feedback 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. No Tel: 781.329.4700 20082016 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. AUX/VBAT/GPIO 6-TO-1 MUX FILTERING PENIRQ/INT/DAV 07667-001AD7879/AD7889 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Auxiliary Input ........................................................................... 18 Applications ....................................................................................... 1 Battery Input ............................................................................... 18 Functional Block Diagram .............................................................. 1 Limit Comparison ...................................................................... 18 General Description ......................................................................... 1 GPIO ............................................................................................ 18 Revision History ............................................................................... 2 Conversion Timing ........................................................................ 20 Specifications ..................................................................................... 3 Register Map ................................................................................... 21 SPI Timing Specifications (AD7879/AD7889) ........................ 4 Detailed Register Descriptions ..................................................... 22 2 I C Timing Specifications (AD7879-1/AD7889-1) ................. 5 Control Registers ............................................................................ 26 Absolute Maximum Ratings ............................................................ 6 Control Register 1 ...................................................................... 26 Thermal Resistance ...................................................................... 6 Control Register 2 ...................................................................... 28 ESD Caution .................................................................................. 6 Control Register 3 ...................................................................... 30 Pin Configurations and Function Descriptions ........................... 7 Interrupts ..................................................................................... 31 Typical Performance Characteristics ............................................. 9 Synchronizing the AD7879/AD7889 to the Host CPU......... 32 Terminology .................................................................................... 12 Serial Interface ................................................................................ 33 Theory of Operation ...................................................................... 13 SPI Interface ................................................................................ 33 2 Touch Screen Principles ............................................................ 13 I C-Compatible Interface .......................................................... 35 Measuring Touch Screen Inputs ............................................... 14 Grounding and Layout .................................................................. 38 Touch Pressure Measurement ................................................... 15 Lead Frame Chip Scale Packages ............................................. 38 Temperature Measurement ....................................................... 15 WLCSP Assembly Considerations ........................................... 38 Median and Averaging Filters ....................................................... 17 Outline Dimensions ....................................................................... 39 AUX/VBAT/GPIO Pin ................................................................... 18 Ordering Guide .......................................................................... 40 REVISION HISTORY 8/2016Rev. C to Rev. D Changes to Pin Configurations and Function Descriptions Section .. 7 Changed CP-16-10 to CP-16-20 .................................. Throughout Added Table 7 ....................................................................................8 Changes to General Description Section ...................................... 1 Changes to First Method Section ................................................. 15 Changes to Figure 7, Figure 8, and Table 7 ................................... 8 Changes to Median and Averaging Filters Section .................... 17 Moved Figure 34 Renumbered Sequentially .............................. 30 Changes to GPIO Interrupt Enable (Bit 12, Control Register 3, Updated Outline Dimensions ....................................................... 39 Address 0x03) Section ................................................................... 19 Changes to Ordering Guide .......................................................... 39 Changes to Table 13 ....................................................................... 22 Changes to ADC Channel (Control Register 1, Bits 14:12 ) 11/2010Rev. B to Rev. C Section .............................................................................................. 26 Changes to Table 2 ............................................................................ 3 Changes to Power Management (Control Register 2, Added Conversion Timing Section .............................................. 20 Bits 15:14 ) Section ........................................................................ 27 Added Figure 34 .............................................................................. 29 Changes to DAVData Available Interrupt Section................. 29 Changes to INTOut-of-Limit Interrupt Section .................... 29 1/2010Rev. A to Rev. B Changes to Writing Data Section ................................................. 31 Updated Outline Dimensions ....................................................... 37 Changes to Reading Data Section and Figure 40 ....................... 32 Changes to Ordering Guide .......................................................... 38 Changes to Figure 41 ...................................................................... 33 2 Changes to Writing Data over the I C Bus Section .................... 34 3/2009Rev. 0 to Rev. A Changes to Figure 44 ...................................................................... 35 Added AD7889 and Backside-Coated WLCSP .............. Universal Updated Outline Dimensions ....................................................... 37 Change to Battery Monitor, Input Voltage Range Parameter ..... 3 Changes to Ordering Guide........................................................ 38 Changes to Table 4 ............................................................................ 6 Added Thermal Resistance Section and Table 5 Renumbered 10/2008Revision 0: Initial Version Sequentially ....................................................................................... 6 Rev. D Page 2 of 40