EVAL-AD7685CBZ

EVAL-AD7685CBZ Datasheet


Evaluation Board For AD768x/AD769x/AD794x/AD798x

Part Datasheet
EVAL-AD7685CBZ EVAL-AD7685CBZ EVAL-AD7685CBZ (pdf)
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Preliminary Technical Data

Evaluation Board For AD768x/AD769x/AD794x/AD798x

EVAL-AD76XXCB 8/10-Pin

Versatile analog signal conditioning circuitry On-board reference, crystal oscillator and buffers 16-bit Parallel Buffered Outputs Ideal for DSP and data acquisition card interfaces Analog and digital prototyping area for breadbording the target system Stand-alone operation or Eval control board compatibility PC software for control and data analysis LabVIEW1 driver to develop custom application
The EVAL-AD76XXCB 8/10-Pin is an evaluation board for the AD768x/AD769x/AD794x/AD798x 8 and 10-pin PulSAR high resolution ADCs see the Ordering Guide at the end of this document for a product list .

The evaluation board is designed to demonstrate the ADC's performance and to provide an easy to understand interface for a variety of system applications. A full description of the

AD768x/AD769x/AD794x/AD798x is available at and should be consulted when utilizing this evaluation board.

The evaluation board is ideal for use with either Analog Devices EVAL-CONTROL BRD2/BRD3 EVAL-CONTROL BRDx , DSP based controller board, to run the Analog devices evaluation software and to develop a specific application using LabVIEW, or as a stand-alone evaluation board.

The EVAL-CONTROL BRDx is sold separately from the evaluation board, is required to run the evaluation software, is not required in stand alone mode and can be reused with many Analog Devices ADCs.
1 Labview is a trademark of National Instruments.

Figure

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. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

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Fax 2007 Analog Devices, Inc. All rights reserved.

EVAL-AD76XXCB 8/10-Pin

TABLE OF CONTENTS

Detailed Description 3 Using the EVAL-AD768x/AD769x/AD794xCB Software 3 Testing Methods 3

Preliminary Technical Data
Use as a Standalone Evaluation Ordering Guide 18 ESD 18

Preliminary Technical Data

EVAL-AD76XXCB 8/10-Pin

Detailed Description

The EVAL-AD76XXCB 8/10-Pin includes a 5V ultrahigh precision reference ADR435 , and a signal conditioning circuit with two opamps ADA4841-x and digital logic. The board interfaces with a 96-way connector for the EVAL-CONTROL BRDx and a 26-pin IDC connector for the serial output interface.

The evaluation board is a four-layer board carefully laid out and tested to demonstrate the specific high accuracy performance of the AD768x/ AD769x/AD794x/AD798x. Figure 2 through Figure 5 show the schematics of the evaluation board. The layouts of the board are shown in the following figures:

Figure 6 Top-Side Silk-Screen

Figure 7 Top-Side Layer

Figure 8 Ground Layer

Figure 9 Shield Layer

Figure 10 Bottom-Side Layer

Figure 11 Bottom-Side Silk-Screen

The evaluation board has a flexible design that enables the user to choose among many different board configurations. A description of each selectable jumper is listed in Table 1, and the available test points are listed in Table

The evaluation board is configured in the factory with the front-end amplifiers U6 and U7 set to a gain of The board is set to be powered through the EVAL-CONTROL BRDx.

Buffered conversion data is available at the output parallel bus BD on U3 and on the 96-pin connector P3 and is valid during the falling edge of BBUSY on P3. Activity of the ADC turns on the on-board LED Power Supplies and Grounding The evaluation board has two power supply blocks:
-SJ1 for the digital interface circuitry and the digital section of the ADC.
-SJ2 for the analog section including the signal conditioning and the reference voltage circuitry.

These offer flexibility to evaluate the ADC and the surrounding circuitry with any power supply combination. Analog Input Ranges and Multiplexing The analog front-end amplifier circuitry U6 and U7 allows flexible configuration changes such as positive or negative gain, input range scaling, filtering, addition of a DC component, and the use of different op-amp and supplies.

The factory configuration of the analog input of U6 and U7 is set at midscale. This allows a transition noise test without any other equipment. An FFT test can be done by applying a very
low distortion AC source.

As an option, an ADG739 multiplexer can be used in front of the ADC to demonstrate performances for multichannel applications.

A second ADC can be mounted on the board to demonstrate the daisy-chain feature.

Using the Software

This configuration requires to use the EVAL-CONTROL BRDx to interface the evaluation board with the PC.

Software Description The evaluation board comes with software for analyzing the AD768x/AD769x/AD794x/AD798x. One can perform a histogram to determine code transition noise, and Fast Fourier Transforms FFT's to determine the Signal-to-Noise Ratio SNR , Signal-to-Noise-plus-Distortion SINAD and TotalHarmonic-Distortion THD . The AC performances can also been evaluated after digital filtering averaging with enhanced resolution up to 32 bits . The front-end PC software has four screens Figure 12 is the Setup Screen where sample rate, number of samples are selected.

Figure 13 is the Histogram Screen, which allows the code distribution for DC input and computes the mean and standard deviation.

Figure 14 is the FFT Screen, which performs an FFT on the captured data, computes SNR, SINAD and THD.

Figure 15 is the time domain representation of the output. When the on-board conversion CNV generation is used, a synchronous FFT can be achieved by synchronizing an external AC generator with the 10MHz Fsync signal J4 a 10 MHz signal, exact division of master clock MCLK .

Figure 16 is the FFT Screen when averaging is used.

Software Installation executable There is no need to have LabVIEW installed to run the executable.

Double-click on Setup.exe in the LabVIEW exe folder from the CD-ROM shipped with the evaluation board do not use the CD shipped with the EVAL-CONTROL BRDx and follow the installation instructions.

Developing your own application using LabVIEW You need LabVIEW or above to do this. Install the executable first, copy the folder LabVIEW VI and run the ADC vi example.vi

Testing Methods Histogram

To perform a histogram test, apply a DC signal to the input. It is

EVAL-AD76XXCB 8/10-Pin
advised to filter the signal to make the DC Source noise compatible with that of the ADC. C26 and C41 provide this filtering. AC Testing To perform an AC test, apply a sinusoidal signal to the evaluation board. Low distortion, better than 100dB, is required to allow true evaluation of the part. One possibility is to filter the input signal from the AC source. There is no suggested band-pass filter but consideration should be taken in the choice. Decimated Testing Averaging This test can be run with a shorted input to evaluate dynamic range or as the AC test. Setup Requirements
• EVAL-CONTROL BRDx ADSP2189
• EVAL-AD76XXCB 8/10-Pin evaluation board
• Power supply AC 12V/1A source could be bought from Analog Devices sold separately from the EVALCONTROL BRDx
• Parallel port cable provided with the evaluation control board
• AC source low distortion
• DC source low noise
The term AD768x/AD769x/AD794x/AD798x is used in this document to represent all the ADCs listed in the ordering guide.
ORDERING GUIDE

Evaluation Board Model EVAL-AD7683CBZ EVAL-AD7684CBZ EVAL-AD7685CBZ EVAL-AD7686CBZ EVAL-AD7687CBZ EVAL-AD7688CBZ EVAL-AD7690CBZ EVAL-AD7691CBZ EVAL-AD7693CBZ EVAL-AD7694CBZ EVAL-AD7942CBZ EVAL-AD7946CBZ EVAL-AD7980CBZ EVAL-AD7982CBZ EVAL-CONTROL BRD2 EVAL-CONTROL BRD3

Product AD7683BRMZ AD7684BRMZ AD7685CRMZ AD7686CRMZ AD7687BRMZ AD7688BRMZ AD7690BRMZ AD7691BRMZ AD7693BRMZ AD7694BRMZ AD7942BRMZ AD7946BRMZ AD7980BRMZ AD7982BRMZ Controller Board Controller Board

ESD CAUTION

ESD electrostatic discharge sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

PR05105-0-3/07 PrG
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Datasheet ID: EVAL-AD7685CBZ 517906