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14-bit ADC, how quiet of a power supply is needed?

I read that having a low-noise power supply is important for 14 to 16 bit ADCs.  My question is how quiet is

quiet enough?  Is a low-noise switcher OK, or is a linear regulator necessary?  LTC (oops!) has some low-noise

switchers with 100-400uVpp output noise.  Is that necessary?  I'd rather use a fairly low noise topology like a

buck-boost and not have to post regulate.  Are there any guidelines?

Thanks,

Roger

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  • Hi Roger, Harry,

    Unfortunately, we do not have any PSRR data for the AD9644.  However, the linear regulator on the AD9644 evaluation board has an output noise of about 250-300uVrms.  Datasheet specifications for AC performance can be achieved with these regulators.  Also, the evaluation board can alternatively be power from and ADP2114 switching regulator.  I do not have a good summary of data on the AD9644 being powered from the ADP2114, but I have a great data point with the AD9268 being powered from the ADP2114.  The AD9268 actually has a lower noise floor (better SNR) and similar SFDR perofrmance and has several similarities in the ADC core design that it shares with the AD9644.  I've inserted a link below.  This gives a good indication of the achievable performance with the ADP2114 and a high performance ADC.  With the right design good performance can be achieved with a switching regulator and a high speed ADC.

    http://www.analog.com/static/imported-files/tech_articles/Powering_High_Speed_ADCs.pdf

    If you can provide your operating frequencies (sample rate, IF, BW, etc.) I can try to get some specific data for you on the AD9644 with the ADP2114 as it only takes a few component changes on the evaluation board to operate the AD9644 with the ADP2114.  The user guide that is downloadable from the AD9644 product page has the information on this.  Just a quick fyi, I will be traveling for the next week, so it may be a delay before I could get some data to you.

    Regards,

    Jonathan

Reply
  • Hi Roger, Harry,

    Unfortunately, we do not have any PSRR data for the AD9644.  However, the linear regulator on the AD9644 evaluation board has an output noise of about 250-300uVrms.  Datasheet specifications for AC performance can be achieved with these regulators.  Also, the evaluation board can alternatively be power from and ADP2114 switching regulator.  I do not have a good summary of data on the AD9644 being powered from the ADP2114, but I have a great data point with the AD9268 being powered from the ADP2114.  The AD9268 actually has a lower noise floor (better SNR) and similar SFDR perofrmance and has several similarities in the ADC core design that it shares with the AD9644.  I've inserted a link below.  This gives a good indication of the achievable performance with the ADP2114 and a high performance ADC.  With the right design good performance can be achieved with a switching regulator and a high speed ADC.

    http://www.analog.com/static/imported-files/tech_articles/Powering_High_Speed_ADCs.pdf

    If you can provide your operating frequencies (sample rate, IF, BW, etc.) I can try to get some specific data for you on the AD9644 with the ADP2114 as it only takes a few component changes on the evaluation board to operate the AD9644 with the ADP2114.  The user guide that is downloadable from the AD9644 product page has the information on this.  Just a quick fyi, I will be traveling for the next week, so it may be a delay before I could get some data to you.

    Regards,

    Jonathan

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