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ADC above maximum MSPS

Fredrik Lundqvist
Prodigy 245 points

Hi,

When I clock a maximum 20 MSPS device I get decent 27 MSPS result with a clock on 27 MHz. How is this possible? Wouldn't some rising edges be missed and result in maximum 20 MSPS even with a higher clock? Or is the maximum sample rate only a recommendation when the output is within the specified accuracy as in the datasheet?

Regards,
Fredrik

  • 0
    TI__Mastermind 29220 points

    Hi,

    are you just saying that you find the device to operate well when clocked at 27MHz even though the datasheet lists a max sample rate for the device of 20MHz?  The max sample rate in the data sheet is not simply a recommendation.  That is the max sample rate that the device is guaranteed to operate at and still meet datasheet specifications over min to max conditions of voltage, temperature, and device-to-device fabrication variation.  A device that just passes production testing at the max sample rate at the extremes of temperature or voltage may be seen work at a much higher rate in the nominal conditions that you may have in your lab, but if you want a large quantity of devices to work and meet spec over temperature and voltage ranges then you would need to heed the data sheet max specifications or else you may find some fallout.

    Regards,

    Richard P.

  • 0 in reply to Richard Prentice
    Prodigy 245 points

    Yes, that was what I meant. Thank you for the explanation, I guessed that this was the case.