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Introduction

The AD7843 is a 12-bit successive-approximation ADC with a synchronous serial interface and low on resistance switches for driving touch screens. The part operates from a single 2.2 V to 5.25 V power supply and features throughput rates greater than 125 kSPS. The external reference applied to the AD7843 can be varied from 1 V to +VCC, while the analog input range is from 0 V to VREF. The device includes a shutdown mode that reduces the current consumption to less than 1 µA. This part is available in a 16-lead 0.15" Quarter Size Outline (QSOP) package and a 16-lead Thin Shrink Small Outline (TSSOP) package. Full data on the AD7843 is available in the AD7843 data sheet (AD7843 Product Page) and should be consulted in conjunction with the EVAL-AD7843CB Technical Note when using the Evaluation Board.

The board has features that allow the user to evaluate all the functions of the AD7843. On-board components include an AD780, which is a pin programmable +2.5 V or +3 V ultra high precision bandgap reference, and two AD713 quad op-amps. There are various link options, which are explained in detail on page 2 of the EVAL-AD7843CB Technical Note.

Interfacing to this board is through a 96-way connector. External sockets are provided for the optional, external, DCLK, CS, and DIN inputs; BUSY, DOUT and PENIRQ outputs; IN3 and IN4 inputs; the VIN input and VBIASED output of the bias-up circuit. External inputs are also supplied to allow the user to easily connect a 4-wire touch-screen panel to the X+, X-, Y+, and Y- inputs.

This evaluation board is compatible with the Evaluation Board Controller which is also available from Analog Devices.

Software

Included in the EVAL-AD7843CB evaluation board package is software for controlling and evaluating the performance of the AD7843 when it is operated with the Evaluation Board Controller. The EVAL-AD7843CB Demonstration/Evaluation Software runs under Windows 95, 98, 2000 & NT. The user interface on the PC is via a dedicated program written especially for the EVAL-AD7843.

To download software, select the link below:

Documentation

Technical notes are available in Adobe Acrobat Portable Document Format (PDF).
To download the Technical Note, select the link below: