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ADC12D1620QML-SP: Acceptable ripple

Elisha Tarroza71
Expert 3700 points
Part Number: ADC12D1620QML-SP

Hello,

A customer is expecting a ripple of about 17mV at the 1.9V supply rail and is concerned about its effects on the performance of the device, specifically on ENOB. 

I've been checking the datasheet, however, there doesn't seem to be a guide specifically for the supply ripple and the ENOB and no PSRR in the electrical specs.

I was wondering if we have information on the acceptable ripple. Could you please share if we any?

Thank you!

  • 0
    TI__Mastermind 38390 points

    Hi Elsiha,

    I am looking into this and trying to get some PSRR data for you on the 1620 ADC. This should help define if 17mV of supply ripple will have an effect on the ADC's performance.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    TI__Mastermind 38390 points

    Hi Elisha,

    I spoke with the design team and there is no PSRR data available on the 1620 ADC.

    If you are interested in setting up the PSRR measurement for yourself, please let me know I can forward a generic setup for this.

    As an example, lets say you have a converter with a 1Vpp input fullscale range that has 56dB of SNR and samples at 1620MSPS. This will give you a noise floor of 19.69nVrms (20nV). This means the noise from any source needs to be below this number.

    Back calc out the noise from the SNR eqn: SNR = 20*log((1/2/sqrt(2))/Noise), Noise = 560.344uV, to get the noise floor simply divide this by the sqrt(Fs/2).

    Now lets say you have 17mVrms presented to the ADC supply pin. As referenced above. Now that the PSRR number found in the measurement and multiply this against the noise at the ADCs supply pin. For our case lets use a PSRR of 60dB (1mV/V). This would be, 17m * 1mV = 17uV.

    Since the 17uV is greater than ~20nV there will be degradation to your SNR, as the power supply noise will be higher than the noise floor. This is assuming your PSRR number is 60dB. It is only a guess. If the PSRR number is lower, say only 40dB, then this puts more emphasis on the power supply noise to be even lower.

    Hope this helps.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    TI__Expert 3700 points

    Dear Rob,

    Thank you very much for your reply. I will forward this information to the customer and let you know if he wants to setup for PSRR measurement. 

    Will it be OK if I email you instead if he does?

    Thanks again for your support. I truly appreciate it.

    Kind Regards,
    Elisha

  • 0 in reply to Elisha Tarroza71
    TI__Mastermind 38390 points

    Hi Elisha,

    You are welcome!

    Yes, you can or the customer can email me.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    TI__Expert 3700 points

    Hello Rob,

    Thanks a lot! We really appreciate the great support :)
    Hope you have a great day, and happy holidays!

    Regards,
    Elisha