CDBCAPTURE CIRRUS | Alldatasheet

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Technical content

Features

lVersatile measurement tool used for the evaluation of Crystal® analog to digital converters. lUpdatable via on-board R AM -based DSP and Altera programmable logic device lEasy interface to a PC compatible computer. lLabW indows® based evaluation software for data analysis. lIncludes time domain, FFT, noise distribution histogram, and DNL analysis options. lCan be used to evaluate the ADC in your equipm ent. lInterfaces to an ADC evaluation board via 10- pin serial ribbon cable or S/PD IF Link. lEnhanced Replacement for the CDBCAPTURE and the CDBCAPTAUDIO General Description The C DBC apture+ interface board is a developm ent tool that interfaces a Crystal® analog to digital converter to a PC -com patible computer. D igital data is collected in a high speed digital SRAM, then transferred to the PC over a serial COM port. Evaluation software is included to an- alyze the data and demo nstrate the analog to digital converter's perform ance. The CDBCa pture+ interface board is designed to be easily interfaced to Crystal evaluation boards. Applica- tion software is loaded via the PC 's serial COM port. The software adjusts the C DBC apture+ interface board for the appropriate signal tim ing and polarity, coding format and numb er of bits, thus allowing the sam e hardware to be used with a variety of Crystal ADCs. Evaluation software is included with the CDBCapture+ interface board. The softw are was developed w ith Lab- Windows® , a s oftware developm ent system for instrum ent control, data acquisition, and analysis appli- cations. The evaluation software permits time dom ain, frequency dom ain, histogram , and DNL analysis. ORDE R ING INFORMATION CDBCap ture+ Signal Source Power Supply Inputs CRYSTAL ADC CDBXXXX EVALUATION BOARD CDBCapture+ +5 V Power Supply Input RS232 Cable IBM Compatible PC Evaluation Software Input Serial Cable S/PDIF Link NOV ‘98 DS32 7F1

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The CDBCapture+ interface board and software are used to capture blocks of serial data from an A/D converter on an evaluation board. This data can be transferred to a PC for analysis and storage. The CDBCapture+ board buffers the digital data in on-board RAM memory and transfers the data to the PC via an RS232 COM port. Figure 1 is a func- tional block diagram that illustrates the data acqui- sition process. The setup for the CDBCapture+ board is simple. A serial cable is connected from the evaluation board to the CDBCapture+ board. This cable will in some cases be a multi-wire conductor and in other cases, depending on the evaluation board being tested, it may be an RCA phono jack or optical in- put for S/PDIF audio data. The interface circuits are provided with electrical isolation between the evaluation board and the CDBCapture+ board to eliminate ground loops. An RS232 cable is con- nected from the CDBCapture+ board to a PC COM port and the PC is loaded with the CDBCapture+ software. An external +5 Volt power supply is re- quired to power the CDBCapture+ board, in addi- tion to any power required for the evaluation board. Upon power-up, the DSP on the CDBCapture+ board starts monitoring the serial COM port for ap- plication software that allows the DSP to program a gate-array on the board to act as an interface for the specific A/D converter on the evaluation board. In this manner, the CDBCapture+ board can be re- programmed to communicate with a large variety of different A/D converters and evaluation boards. Once the on-board gate-array is programmed, the data collection process is started by sending a com- mand from the PC to the CDBCapture+ board. LED indicators on the CDBCapture+ board indi- cate system status during acquisition of data from the evaluation board and during transfer of data to the PC. The CDBCapture+ board can be directed to collect one or, depending on the A/D converter being evaluated, two channels of data from the evaluation board. The data is stored in an on-board RAM until data acquisition is complete, then upon command from the PC, it is sent to the PC via the RS232 COM port. The evaluation and display software provided for the PC was developed using LabWindows and per- forms the post processing of the digitized signals. Time plots, FFT analysis, noise analysis, and dif- ferential nonlinearity (DNL) analysis are included. The software allows as many as 32768 samples to be acquired and analyzed. DNL analysis is sup- ported only for converters with 16 bits or lower res- olutions. For more sophisticated data analysis, the LabWindows® development system can be pur- chased from National Instruments (512-794-0100). LabW indows is a registered tradem ark of National Instrum ents Corp. Preliminary product inform ation describes products which are in production, but for which full characterization data is not yet available. Advance product information describes products which are in developme nt and subject to developme nt changes. Cirrus Logic, Inc. has made best efforts to ensure that the information contained in this documen t is accurate and reliable. However, the information is subject to change without notice and is provided “AS IS” without wa rranty of any kind (express or im plied). No responsibility is assum ed by Cirrus Logic, Inc. for the use of this information, nor for infringeme nts of patents or other rights of third parties. This docum ent is the property of Cirrus Logic, Inc. and imp lies no license under patents, copyrights, tradema rks, or trade secrets. No part of this publication may be copied, reproduced, stored in a retrieval sys- tem, or transmitted, in any form or by any means (electronic, mechanical, photographic, or otherw ise). Furthermore, no part of this publication may be used as a basis for manufacture or sale of any items w ithout the prior written consent of Cirrus Logic, Inc. The names of products of C irrus Logic, Inc. or other vendors and suppliers appearing in this docume nt may be tradem arks or service marks of their respective owne rs

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ing in on a group of points for a more detailed view. Figure 2. Startup Screen Figure 3. T ime Dom ain A nalysis

Distortion (S/D), and Signal to Noise Ratio (SNR). FFT to discern the fundamental from the DC bins. grounded input FFT is shown in Figure 5. Figure 4. Frequency D om ain Analysis

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Figure 6 shows the results of a Histogram Analysis. input to the evaluation board and acquiring data. COUNT values shown to the left of the histogram. will yield the peak to peak noise. of a converter's Differential Nonlinearity (DNL). converter has perfect differential nonlinearity. Figure 5. Groun ded Input FFT

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Figure 8. D ifferential Nonlinearity Histogram

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