6 Using the ADS8472EVM
6.1 As a Reference Board
6.2 As a Prototype Board
6.2.1 Evaluation Board
6.2.2 EVM and TSW1100 Capture Card
Using the ADS8472EVM
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The ADS8472EVM serves the functions of being a reference design, a prototyping board, and finally as ansoftware test platform.
As a reference design, the ADS8472EVM contains the essential circuitry to showcase the analog-to-digitalconverter. This essential circuitry includes the input amplifier, reference circuit, and buffers. TheADS8472EVM analog input circuit is optimized for a wide bandwidth signal; therefore, the user may needto adjust the input buffer circuitry to better suit your needs. In AC-type applications where signal distortionis a concern, the user should use high quality capacitors such as Mica, polypropylene or COGs typecapacitors in the signal path. In applications where the input is multiplexed, the A/D input resistor andcapacitor may need to be adjusted further.
As a prototype board, the ADS8472EVM features amplifiers in a standard 8-pin SOIC package and manyresistor pads scattered around allowing the user to experiment with a host of circuits, as needed. TheADS8472EVM can be used to evaluate both dual- and single-supply amplifiers in both inverting andnon-inverting configurations. The ADS8472EVM comes installed with a dual-supply amplifier which allowsthe user to take advantage of the full input voltage range of the converter. For applications that requiresignal supply operation and smaller input voltage range, the THS4031 can be replaced with thesingle-supply amplifier like the OPA300 or OPA350. Pad jumper SJP3 should be shorted between pads 1and 2. This shorts the minus supply pin of the amplifier to ground. Positive supply voltage can be appliedat test point TP4 or at connector J5 pin 1.
There are two common methods to evaluate the ADS8472EVM’s performance.1. EVM used as a stand-alone system. The user is responsible for capturing and analyzing the data,typically via a logic analyzer and analysis software (LABView, MATLAB, etc)2. EVM used in conjunction with TI’s TSW1100 data capture card,http://focus.ti.com/docs/toolsw/folders/print/tsw1100.html
The following section discusses method two.
The User’s Guide for the data capture card is available at http://focus.ti.com/lit/ug/slau155a/slau155a.pdf .Refer to this guide for detailed information and set-up instructions.
The ADS8472EVM mates with the TSW1100 card via J7. There are two data ports available on thecapture card, the reference designators are J1 and J2. The ADS8472EVM can be plugged into either port.
The TSW1100 is a data capture card and provides no control signals to the ADS8472. The ADS8472requires a CONVST pulse to begin digitizing the signal. Therefore, the user must provide a CONVST tothe ADS8472 at P3 pin 17 or at J6 pin 5 on the ADS8472EVM. In this case, it is recommended theADS8472 be operated in the CS and RD tied low mode, as this requires only CONVST to toggle. To shortthis signals to ground, simply short across pins 1 and 2, and 3 and 4 of J6, respectively. The digitized datais available on the data bus at the end of every busy cycle. In this operating scheme, the inverted BUSYsignal is used to trigger the TSW1100 card to read the data bus. To avoid line contention remove jumpersfrom W3, W4, W5, and W6 on the ADS8472EVM.
The ADS8472 EVM is supported with the TSW1100 capture card firmware release 1.x. Please use theADS1610EVM entry as a template for acquiring data from the ADS8374EVM. Due to hardware limitationson the TSW1100 platform, data capture from the ADS8472EVM is restricted to 1MSPS minimum.
ADS8472EVM 8 SLAU203 – February 2007Submit Documentation Feedback
