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Frequency-varying sample clock with the ADC08D1020

Alexander Walsh
Prodigy 20 points
Other Parts Discussed in Thread: ADC08D1020

Hello,

  I'm developing a data acquisition system for a swept source optical coherence tomography system.  I would prefer to directly sample of the k-clock to avoid the processing step of re-sampling the data.  My k-clock will be frequency varying over time from approximately 340 MHz to 740 MHz.  The frequency vs. time behavior is roughly shown in the figure below.

I would like to know if it is possible to use this type of signal (provided it meets other electrical specifications) as the sample clock input for the ADC08D1020.  I suspect the relevant clock specifications are minimum frequency (200 MHZ per datasheet), maximum frequency (1 GHz) and clock duty cycle (20%-80%).  This makes me think I should be able to use this ADC chip, but I would appreciate any help or thoughts on the matter.  Are there other important clock specifications to be aware of for this sort of sampling?

Thank you for your time.  I am happy to discuss in further detail or elaborate if necessary.

-richard

  • 0
    TI__Mastermind 44680 points

    Hi Richard

    The ADC should be able to support this type of frequency variation without significant performance degradation. Changing the frequency at a few hundred MHz per microsecond does not significantly affect the duty cycle of the clock, which is one of the main factors to consider.

    Also, since we recommend calibrating the device at the normal operating frequency and stable operating temperature I would recommend that the device calibration be done in the middle of the clock frequency range where the useful data is being captured. To do this I would set a static clock frequency at that point and trigger the device calibration. Once the device is calibrated you can enable the modulated clock waveform.

    The other challenge I see is designing the data capture system (FPGA?) to operate with a variable DCLK frequency. We have not tried to implement something of this nature, so I don't have any recommendations for that aspect of the system.

    I hope this is helpful.

    Best regards,

    Jim B