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AD7879:  Low Voltage Controller for Touch Screens

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 ...More

AD7879:  Low Voltage Controller for Touch Screens

Product Description

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 (DAV), as an interrupt to indicate when limits are exceeded (INT), or as a pen-down interrupt when the screen is touched (PENIRQ). The AD7879/AD7889 offer temp-erature 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 hand-held devices
  • Touch screen monitors
  • Point-of-sales terminals
  • Medical devices
  • Cell phones

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EVALUATION BOARDS & DEVELOPMENT KITS

  • 4-wire touch screen interface
  • 1.6V to 3.6V 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
  • See data sheet for additional features.
  • Resolution (Bits): 12bit
  • T-Put Rate: 105kSPS
  • # Chan: 6
  • Supply V: Single(+2.7),Single(+3),Single(+3.3)
  • Pwr Diss: 2.3mW
  • Interface: I²C/Ser 2-Wire,Ser,SPI
  • Ain Range: Uni Vdd
  • SNR (dB): n/a
  • Pkg Type: CSP

Functional Block Diagram for AD7879

Similar Products

arrow View Full Interactive Product Selection Table
Part# Bits Throughput Rate # of Inputs Operating Pwr Diss
AD7889 12 105KSPS 6 2.3mW
AD7879 12 105KSPS 6 2.3mW
AD7466 12 200KSPS 1 900µW
AD7658-1 12 250KSPS 6 140mW
AD7658 12 250KSPS 6 143mW
AD7467 10 200KSPS 1 630µW
AD7468 8 200KSPS 1 570µW
AD7888 12 125KSPS 8 3.5mW
AD7991 12 140KSPS 4 4.68mW
AD7994 12 188KSPS 4 6mW
AD7927 12 200KSPS 8 7.5mW
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*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.
**Sample availability may be better than production availability. Please enter samples into your cart to check sample availability.