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SNR for ADC3101 vs. PCM1863

Ed Arrington
Prodigy 90 points
Other Parts Discussed in Thread: PCM1863, TLV320ADC3101

A look at the spec sheet for the ADC (ADC3101) shows this data:

While the “Typical” spec is 92dB, the minimum value is 80dB.  In our tests, we appear to be getting the minimum.  That’s a little disappointing, of course.

The second thing I notice is that the "typ" spec is 92dB SNR when the IN1 input is selected and is “ac-shorted to ground.” That suggests that the input signal is 0vDC.  Is that right?

Now, compare this to the specs in the TI PCM1863:

 

Aside from the much better minimum SNR of 97dB, the test signal in this case is an actual -60dB signal with the PGA gain at 0dB.  Does that mean that with a -60dB signal, that the noise is at least 97dB lower than the input signal of -60dB?  Does that mean that the noise is actually an inaudible -180dBFS?

Looking at the second row where they take a -92dB input signal, push it up 32dB with the PGA (resulting presumably in a -60dB signal), we still have an S/N of 93dB? (which would suggest the noise down at -153dBFS?)

Further, is the difference between SNR on the ADC3101 and PCM1863 actually that significant or am I missing something?

Thanks!

  • 0
    TI__Guru* 84915 points
    Hi, Ed,

    All your assumptions about the SNR differences between both devices are correct. The difference between the SNR on both devices is that significant. Also, the SNR tests conditions are different as you already mentioned. In case of the TLV320ADC3101, there are some additional conditions at the bottom of the table (marked by (1) and (2)).

    Please let me know if you have more questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.
  • 0 in reply to Luis Fernando Rodriguez S.
    TI__Guru* 84915 points
    Hi, Ed,

    I made a mistake about the PCM1863 measurements. Actually, the measurement is made at -60dB and then it is added 60dB back to get -97dB. This means that the noise floor is -37dB lower than the -60dB input tone. For more information, you may read more about the AES17 standard.

    Best regards,
    Luis Fernando Rodríguez S.