SBAU042 – MARCH 2001
FEATURES
q PROVIDES FAST AND EASY
PERFORMANCE TESTING FOR ADS1252q PC SERIAL PORT CONTROLq WINDOWS® 95/98 SOFTWARE
Windows is a registered trademark of Microsoft Corp.
DESCRIPTION
The ADS1252EVM demo board is designed for ease of usewhen evaluating the high-resolution analog-to-digital con-verter ADS1252. The ADS1252 offers 24-bits No MissingCodes performance. It has one differential input channel.The ADS1252 features a synchronous serial interface. It hasbeen designed for closed-loop control applications in theindustrial process market and high-resolution applications inthe test and measurement market. It is also ideal for remoteapplications, battery-powered instruments, and isolated sys-tems.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.Products conform to specifications per the terms of Texas Instrumentsstandard warranty. Production processing does not necessarily includetesting of all parameters.
Copyright © 2001, Texas Instruments Incorporated
www.ti.com
INITIAL CONFIGURATION
The ADS1252EVM is designed to be operational withoutany user configuration except for connecting power suppliesand the communications cable to the PC serial port. JumpersJMP1 (Clock Oscillator), JMP3 (DUT clock), JMP8(ADS1252 power), and JMP10 (reference select) have al-ready been installed.POWER SUPPLY
The demo board is powered from an 8V to 12V powersource. That voltage is regulated to 5V for use of theADS1252 and the microprocessor.VOLTAGE REFERENCE
Jumper JMP10 is used to select the source for the referencevoltage. If the jumper is placed on the two pins closest to theBNC connector, the BNC connector will be selected as thesource of the reference voltage. If the jumper is placed on thetwo pins away from the connector, then the on-board 4.096Vreference is chosen. The selected voltage is buffered with anOPA350 op amp for the use of the ADS1252.CLOCK
The 50MHz crystal oscillator provides the operating fre-quency for the microprocessor. The processor in combina-tion with a PLL provides a clock for the ADS1252.PC BOARD LAYOUT
The ADS1252EVM demo board consists of a four-layer PCboard. To achieve the highest level of performance, surface-mount components are used wherever possible. This reducesthe trace length and minimizes the effects of parasitic ca-pacitance and inductance. The demo board has a split groundplane with all the analog signals over one portion and thedigital signals in the other. Keep in mind that this approachmay not necessarily yield optimum performance resultswhen designing the ADS1252 into different individual ap-plications. In any case, thoroughly bypassing the powersupply and reference pins of the converter is strongly recom-mended.
FIGURE 1. Demo Properties.
The program has two windows: 1) The Control Window and2) The Data Display Window. The Control Window canAcquire data, set the frequency for data acquisition andselect the PC communications port.
In the Get Data, shown in Figure 2, screen the number ofsamples can be set from 32 to 32768 points. Each data pointcan be raw data from the ADS1252 or the points can be theresult of averages of the Analog-to-Digital (A/D) converterdata. Up to 32,768 averages can be performed for eachoutput data point.
WINDOWS SOFTWARE
The serial port used for communications can be specified onthe command line. Just add “port1”, “port2”, etc. after thecommand in the Target field, as shown in Figure 1. It canalso be specified in the program.
The ADS1252 is very easy to use. Basically, supply a clockand read the output data. The Evaluation software providesa convienent method to vary the operation and observe theresults. It also can display the results of acquired data andperform a frequency analysis.
FIGURE 2. Initial Control Window.
The Power Down button will put the part into a low-powerstate. Collect Data will return the part to the full-powerstate. The power-down state will only reduce the demoboard current by about 1mA. For detailed power analysis,use JMP8 to power the part from an external source.
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The Frequency screen, shown in Figure 3, lets you choosethe operating frequency of the device. The frequencies of2kHz, 10kHz, and 35kHz give good noise performance.Although, by selecting Variable Sample Rate, other samplerates can be selected by choosing the output sample rate orthe clock frequency (Sample Rate • 384). The noise perfor-mance is not as good when using the Variable Sample Ratebecause of the PLL used to generate the clocks.
Along the top of the Time Domain Display, shown in figure 5,are icons that can be used to select the various displaymodes. The four displays are 1) Time Domain, 2) FFT,3) Histogram, and 4) Data List. Statistics for the data are alsodisplayed on the top of the Time Domain Display. It showsthe Standard Deviation, Mean, Maximum, and Minimum.
FIGURE 3. Frequency Window.
The Options screen, shown in Figure 4, gives you control ofwhich serial port the program will use when it communi-cates with the evaluation module. This is also where youspecify the reference voltage used to normalize the data fora “scaled by LSB” voltage display.
FIGURE 5. Time Domain Display.
Several figures of merit are computed from the FFT infor-mation shown in Figure 6. These include the Signal to NoiseRatio (SNR), Signal to Noise plus Distortion (SINAD),Total Harmonic Distortion (THD) and Spurious Free Dy-namic Range (SFDR).
FIGURE 4. Configuration Window.
FIGURE 6. FFT Display.
ADS1252EVM
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There are many options for the FFT display. The optionsmenu selection opens the screen shown in Figure 7.
Several windows are provided to modify the data before theFFT computation. Additionally, the FFT display can marksome features such as the main frequency and the harmon-ics.
Finally, the data can be analyzed in detail with the Data Listdisplay shown in figure 8.
The Data Formats can be selected. This selection will also beused for the display of the date in the Time Domain display.The “Scaled by LSB” converts the data to a voltage with theassumption that the voltage reference is as defined in Figure 4.FIGURE 7. FFT Options.FIGURE 8. Data List Display.
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FIGURE 9. Schematic
ADS1252EVM
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COMPONENT LIST
PART NUMBERADS1252UB3F-1050CRCW120610R0FCRCW1206000CRCW12061001FCRCW12061002FCRCW12062000CRCW12064991FC1206C101K5GACC1206C103K5RACC1206C104K5RAC
DESCRIPTION
IC, A/D CONV, 24-BIT,20kHzSWITCH, SPST, PB-MOM
RES, 10.0Ω, 0.125W, 1%, CHIP-THICK-FILMRES, 0.0Ω, 0.125W, 0%, CHIP-JUMPERRES, 1.0kΩ, 0.125W, .1%, CHIP-THICK-FILMRES, 10.0kΩ, 0.125W, 1%, CHIP-THICK-FILMRES, 200Ω, 0.125W, 1%, CHIP-THICK-FILMRES, 4.99kΩ, 0.125W, 1%, CHIP-THICK-FILMCAP, 100pF, 50V, 10%, CHIP-CERAMIC COGCAP, .01uF, 50V, 10%, CHIP-CERAMIC X7RCAP, 0.10uF, 50V, 10%, CHIP-CERAMIC X7R***
C1206C221K5GACICD2053BSC-1LM4040AIM3-4.1LM7805CTMAX232ACSEOPA350UAOTS-(8)16-1.27-03RUE090SK14SX52BD/PQTC551001/CFT-70LTNPW12061001BTSW-102-07-L-S
CAP, 220pF, 50V, 10%, CHIP-CERAMIC COGIC, PROGRAMMABLE CLOCK GENERATORIC, PREC. VREF 4.1V, 0.1% SOT-23
3-TERM. 5V/1A POS. FIXED REGULATOR, TIC, DRVR/RCVR, RS-232 +5VOPAMP, CMOS, SINGLE-SUPPLYSOCKET, SO-8 OTS16 SERIES
FUSE, 30V, RESETTABLE POLYSWITCHDIODE, SCHOTTKEY, 40PIV,1.0AIC, uPROC, 4k WORD 50MHz.IC, MEMORY 1Mb X 8-BIT SRAMRES 1k 1/8W .1%
CONN, 2 POS .1 CTR .025 SQ. POST * *
TSW-103-07-L-STSW-104-07-L-STSW-105-07-L-ST491D106K035ASVF161SHHL2SV-02227699-1745781-4
Total Parts Used: 80
CONN, 3 POS .1 CTR .025 SQ. POSTCONN, 4 POS .1 CTR .025 SQ. POSTCONN, 5 POS .1 CTR .025 SQ. POST
CAP, 10uF, 35V, 10%, TANTALUM CHIP-MOLDEDIC, HYBRID XTAL OSC ,VERY HI SPEED
TERM. BLK, 2 POS LEVER POWER CONNECTORCONN, JACK, BNC, PCB MNT, VERTICAL, 50Ω
REF. DES.U6SW1R19R5,R6,R17R18
R1,R7,R8,R14R2,R3,R4R9,R15,R16C12,C20C17
C1,C2,C3,C4,C5,C6C7,C8,C9,C10,C11C15,C18,C21,C23,C24C25,C26,C27,C28C22U4VR1U10U3U7,U8,U9U5F1CR2CR1U1U2
R10,R11,R12,R13
JMP1,JMP2,JMP3,JMP4JMP5,JMP6,JMP7,JMP8JMP9,JMP11JMP10J1J3
C13,C14,C16,C19pX1J4J5,J7
11141121
TSW-103-07-L-S TSW-104-07-L-S TSW-105-07-L-S T491D106K035AS VF161SHHL 2SV-02 227699-1 745781-4
KEMET
111113111111410
C1206C221K5GAC ICD2053BSC-1 LM4040AIM3-4.1 LM7805CT MAX232ACSE OPA350UA OTS-(8)16-1.27-03
RUE090 SK14
SML-LX1206-GC-TR
SX52BD/PQ TC551001/CFT-70L TNPW12061001B TSW-102-07-L-S
National Semi KEMET
QTYVENDOR PART NUMBERMANUFACTURER111314332120
ADS1252U B3F-1050 CRCW120610R0F CRCW1206000 CRCW12061001F CRCW12061002F CRCW12062000F CRCW12064991F C1206C101K5GAC C1206C103K5RAC C1206C104K5RAC
DALE DALE DALE DALE DALE DALE KEMET KEMET KEMET
SML-LX1206-GC-TRLED, SMT 1206, GREEN
CONN, DB9, RECPT .318 STYLE WITH STD HDWRJ2
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