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ADC34J44EVM: Maximum Sample Rate and available config files

Chanci King
Prodigy 30 points
Part Number: ADC34J44EVM
Other Parts Discussed in Thread: LMK04828

Hi,

There are 3 available config files for the ADC3xJxxEVM using the HSDC Pro GUI  - 80 MSPS, 128 MSPS, and 160 MSPS. I am using the ADC34J44EVM where the maximum clock frequency is 125 MHz. Is there any reason that a 125 MSPS config file is not available instead of the 128 MSPS?

If I use the 128 MSPS config file and set my sampling rate to 128M, is there anything I should be weary of given that it is greater than what has been rated as the maximum clock frequency?

Thanks,

CK

  • 0
    TI__Genius 12780 points
    Hi CK,

    Functionally, the 128 MSPS configuration file will work for the ADC34J44EVM; However, performance may not coincide 100% with data sheet specifications.

    Best Regards,

    Dan
  • 0 in reply to dBrock
    Prodigy 30 points
    Thanks, Dan. If I wanted to update the config file to 125 MSPS, how would I do that? I've been seeing more of a performance degradation with increased frequency than would be expected if compared to table 7.10 of the spec sheet and now I'm wondering if this might be my issue.

    -CK
  • 0 in reply to Chanci King
    TI__Genius 12780 points

    Hi CK,

    Please try the attached procedure, which utilizes a signal generator as an input to the LMK.

    6305.External Clock.zip

    Best Regards,

    Dan

  • 0 in reply to dBrock
    Prodigy 30 points
    I'm just trying to understand why it is possible to operate at 128 MHz but not 125 MHz using the 100 MHz VCXO on the EVM board. I understand that 80, 128, and 160 are all values obtained by dividing 2560 MHz by divider values set in the 0x100 register, but I haven't figured out how 2560 MHz is being generated from the 100 MHz VCXO. Its not always going to be convenient for me to have a signal generator with me while operating this, so I would like to understand if it is at all possible to get to 125 MSPS with just changing the config files.
  • 0 in reply to Chanci King
    TI__Genius 12780 points

    Hi CK,

    You are absolutely correct. This frequency can be generated by the LMK using the software TICS Pro.

    http://www.ti.com/tool/TICSPRO-SW

    You can generate register settings for a desired frequency. I have created a configuration file for 125 MSPS operation for the ADC34J44EVM, but it appears that there is a 100 kHz difference in frequency. I input a 1 MHz signal, and the FFT shows a 999.451 kHz signal.

    I do believe that the LMK04828 is capable of producing a solid 125 MSPS based off of the 100 MHz input reference, but I do not have the expertise to troubleshoot this issue further. Please make a post in the HSDC-CTS forum for further assistanceADC3xJxx_125MSPS_Operation_LMK_SettingC.cfg.

    Best Regards,

    Dan