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ADS1258EVM-PDK: DC Waveforms

Errol Leon6
Expert 5850 points
Part Number: ADS1258EVM-PDK
Other Parts Discussed in Thread: ADS1258, ADCPRO

Hello team,

My customer is planning to use ADS1258 in their system. They ordered the ADS1258EVM and have some questions below regarding it:

1. How do I check the accuracy of a DC waveform. The signal generator on EVM board gives me an option to generate Sine, Ramp , Square and many other but not the DC one.

2. Also what other tests, I should perform on this ADC to characterize it well for our use in the system. My assumption is to check for ENOB, Resolution, and linearity errors. But can you provide some inputs on how to check these parameters with ADC itself or with its EVM in lab?

Thank you in advance for your support!

Errol

  • 0
    TI__Guru 52576 points

    Hi Errol,

    To check the accuracy of a DC waveform, you would generally apply a DC input from a signal source, then measure back the input voltage using a high precision meter. Then, you would compare this result to the ADC's output to determine the ADC's accuracy.

    In order to characterize the ADC for use in a system, it would be helpful to know what the ADC is measuring. But in general you could perform an input-short test to characterize the noise of the ADC, or measure it's offset. If you want to determine AC ENOB, you would apply some AC signal, measure the SNR and then calculate the ENOB. For linearity, you would do the same but measure the THD.

    Let me know if this answers your questions.

    -Bryan

  • 0 in reply to Bryan Lizon86
    TI__Expert 5850 points

    Thanks Bryan for your quick reply. It certainly helps. They are measuring DC signals through this ADC.

    To confirm their setting for DC accuracy test, I am writing the steps here. Please correct me if there is something wrong here:

    • Apply input on any of analog input channels on J1,or J2 connector (A1-A15). To measure the output, do I measure in between pins J2.14(MUXOUP) and J2.16(MUXOUN) or Should I configure one of GPIOs on J3 as output and then measure the output there?
    • And If I have to test this ADC, which is not on available on this demo board but on a custom board.  Can I connect the ADC and its inputs of custom board to MMBO(Modular EVM Motherboard) J7 connector (A1-A8). And if I can then, do I measure the output in same way as step 1? Basically, I am trying to find out, how to use the ADCPro software with MMBO DSP (TMS320) with an ADC, which is present on a custom board.

    • I can certainly perform the noise test by shorting the inputs and measure the offset.

    Please let me know if  I am not clear in my questions.

    Thanks again for your help!

    Errol

  • 0 in reply to Errol Leon6
    TI__Guru 52576 points

    Hi Errol,

    Maybe I misread your first question, but you would measure the input using a high precision meter, then read out data from the ADC and compare the two results. This will give you an indication of how close the ADC's analog input is to it's digital output. You could apply the offset and gain calibrations before and after these measurements, to see how much the calibration routine impacts the overall accuracy.

    Regarding the MMB0 board: it is possible that you will be able to connect the customer ADC board to the MMB0, but it will likely not be an easy task. In some cases the MMB0 board requires information from the daughter card (usually stored in an EEPROM) to ensure it is speaking to the correct device. Without this information, the MMB0 won't function. This is just one of many potential problems when trying to hook up a custom board. Our general recommendation would be use the MMB0 board with an appropriate daughter card from TI, and if you choose to use a custom board that this is done at your own risk.

    -Bryan