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AD7889:  Low Voltage Controller for Touch Screens

Product Details


The AD7879/AD7889 are 12-bit successive approximation analog-to-digital converters (SAR ADCs) with a synchronous serial interface and low on-resistance switches for driving 4-wire resistive touch screens. The AD7879/AD7889 work with a very low power supply—a single 1.6 V to 3.6 V supply—and feature throughput rates of 105 kSPS. The devices include a shutdown mode that reduces current consumption to less than 6 μA.

To reduce the effects of noise from LCDs and other sources, the AD7879/AD7889 contain a preprocessing block. The prepro- cessing function consists of a median filter and an averaging filter. The combination of these two filters provides a more robust solution, discarding the spurious noise in the signal and keeping only the data of interest. The size of both filters is programmable. Other user-programmable conversion controls include variable acquisition time and first conversion delay; up to 16 averages can be taken per conversion. The AD7879/AD7889 can run in slave mode or standalone (master) mode, using an automatic conversion sequencer and timer.

The AD7879/AD7889 have a programmable pin that can operate as an auxiliary input to the ADC, as a battery monitor, or as a GPIO. In addition, a programmable interrupt output can operate in three modes: as a general-purpose interrupt to signal when new data is available (DAVINT), or as a pen-down interrupt when the screen is touched (PENIRQ). The AD7879/AD7889 offer temperature measurement and touch-pressure measurement.

The AD7879 is available in a 12-ball, 1.6 mm × 2 mm WLCSP and in a 16-lead, 4 mm × 4 mm LFCSP. The AD7889 is available in a backside-coated version of the WLCSP. Both parts support an SPI interface (AD7879/AD7889) or an I2C® interface (AD7879-1/AD7889-1).

Applications

  • Personal digital assistants
  • Smart handheld devices
  • Touch screen monitors
  • Point-of-sale terminals
  • Medical devices
  • Cell phones

FEATURES and BENEFITS

  • Chinese data sheet available
  • 4-wire touch screen interface
  • 1.6 V to 3.6 V operation
  • Median and averaging filter to reduce noise
  • Automatic conversion sequencer and timer
  • User-programmable conversion parameters
  • Auxiliary analog input/battery monitor (0.5 V to 5 V)
  • 1 optional GPIO
  • Interrupt outputs (INT, PENIRQ)
  • Touch-pressure measurement
  • Wake-up on touch function
  • Shutdown mode: 6 μA maximum
  • 12-ball, 1.6 mm × 2 mm WLCSP
  • 16-lead, 4 mm × 4 mm LFCSP

Functional Block Diagram for AD7889

Documentation

Title Content Type File Type
AD7879/AD7889: Low Voltage Controller for Touch Screens Data Sheet (Rev C, 11/2010) (pdf, 719 kB) Data Sheets PDF
MS-2210: Designing Power Supplies for High Speed ADC  (pdf, 327 kB) Technical Articles PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Design Tools,Models,Drivers & Software

Title Content Type File Type
AD7879 Input Touch Screen Digitizer Linux Driver Device Drivers HTML

Evaluation Kits & Symbols & Footprints

Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

SampleSample & Buy

Price, packaging, availability

AD7889 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD7889-1ACBZ-500R7 Status: Production 12 Ball WLCSP (1.61x2.01) 12 Ind Reel, 500 - $1.69 Y  Material Info PCN/PDN Purchase Sample
AD7889-1ACBZ-RL Status: Production 12 Ball WLCSP (1.61x2.01) 12 Ind Reel, 10000 - $1.69 Y  Material Info PDN Purchase
AD7889-1ACBZ-RL7 Status: Production 12 Ball WLCSP (1.61x2.01) 12 Ind Reel, 3000 - $1.69 Y  Material Info PCN/PDN Purchase
AD7889ACBZ-500R7 Status: Production 12 Ball WLCSP (1.61x2.01) 12 Ind Reel, 500 - $1.69 Y  Material Info PCN/PDN Purchase Sample
AD7889ACBZ-RL Status: Production 12 Ball WLCSP (1.61x2.01) 12 Ind Reel, 10000 - $1.69 Y  Material Info PDN Purchase
Price Table Help

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


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