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ADS131A04: Using a 16MHz Crystal in place of 16.384MHz

Part Number: ADS131A04

Hi,

I am using an ADS131A04 in one of my designs which I am currently clocking using a 16.384MHz Crystal (Connected to XTAL1 and XTAL2 pins, through the required R/C network) as used in the EVM Reference design. The system is working fine. I wish to replace the crystal with a 16MHz Crystal (not a buffered oscillator), as this will provide me sampling rates which would reduce the resampling overhead in my DSP considerably. Now, the data sheet lists 16.384MHz as the nominal XTAL Clock Frequency and 16.5MHz as the maximum XTAL Clock frequency. There is no specified minimum limit. Will there be problems if I use a 16MHz crystal with the same load capacitance values? Will it work ? Are there any other issues that I should consider while doing this ?

Any comments or replies will be deeply appreciated.

Thanks and Regards

Ajith Peter

  • Ajith,


    I don't know of any problems of using a lower frequency crystal for this device and we don't specify a lower XTAL frequency for operation. However, there are can be issues with crystal startup and that's why we give recommendations on which crystals to use so that the oscillator startup isn't in question. See page 27 in the datasheet for more details.

    It is likely that the 16MHz crystal won't be much different than the 16.384MHz crystal for crystals in the same product line. If you test out the crystal and there are issues in the startup, I would start with smaller load capacitances as the board often has some parasitic capacitance adding to the load.

    However, I think the safest thing would be to use a real clock line, sending in a 16MHz clock into the XTAL1/CLKIN pin instead of using a crystal.

    Because you're using a different frequency (16MHz instead of 16.384MHz), there will be a modest change in the data rate, and maybe some changes in the clock timing (looking for anything that changes with the clock frequency), but for the most part, the operation should be similar.


    Joseph Wu
  • Joseph,

    Thank you very much for the reply.  I verified it with a 16MHz crystal and the output sample rate is coming as expected. 

    Thank you very much for the assurance.  In the next revision of the design, I will be going for a proper 16MHz clock line.

    Regards

    Ajith