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Using a ADC EVM board with DC input

Andrew Macpherson
Prodigy 70 points

I would like an ADC evaluation board, along with a data capture board, to perform tests using a high-speed ADC.  I have selected the ADS5520EVM and TSW1100EVM boards for this purpose.

My question is this: for one of my tests, I would like to apply DC input to the ADC (either single-ended or differential). Will this be possible with these boards? I have read through the relevant datasheets and I think that if the board is configured for differential amplifier input, rather than transformer-coupled input, it will work with DC inputs (either single-ended or differential). Can anyone confirm whether this will work?

  • 0
    TI__Genius 12965 points

    Andrew,

     

    As you stated for DC inputs you will have to bypass the transformer path and use the differential amplifier path.  Look at section 2.2.1 of the users guide for details on the required connections.

     

    KC

  • 0 in reply to Ken C
    Prodigy 70 points

    Thank you for the reply. I have now bought the EVM board (ADS5520EVM) and am preparing to test it.  I have a question:

    In the schematic, it shows R22 and R35 (resistors connected to the ouputs of the differential amp) as 402 ohms.  However in the parts list R22 and R35 are listed as "not installed" beside both 24.9 and 36.5 ohms.  Which should I install: 24.9, 36.5 or 402 ohms? Or what are the considerations to choose between them?

  • 0 in reply to Andrew Macpherson
    TI__Genius 12965 points

    Andrew,

    Sorry for the late reply, I missed this in my inbox - I hope you figured out the resistor issue.  The R22 should be 49.9 and R35 should be 100 ohms.  There is no mention of the 36.5 ohms in the released EVM schematic and BOM.  The default configuration should allow you to connect a 50 ohm piece of test equipment to the ADC input SMA.

    Regards,

    Ken.