Tool/software:
Hi team,
Form the product page, the device is 10-bit converter
But I see the datasheet, and this register, it seems that ADC3910 can work as 16-bit
How can I understand? It is just a 10-bit, but just fill the register as 16-bit? (shift register)
Regards,
Hayashi
Hi Hayashi,
See the plot below:
The ADC can be considered an almost perfect 10-bit quantizer; therefore, when you decimate, you get a 3dB improvement in SNR for every factor of 2 of decimation (this is because you reduce the effective noise BW by 2).
In theory, 10-bit resolution gives max SNR of 61.96dB, 12-bit resolution gives max SNR of 74dB, and 16-bit resolution gives max SNR of 98.08dB.
The device supports up to decimation by 16 so SNR can be a maximum of 74dB. In this case, the 10-bit and 12-bit modes can limit the SNR due to quantization noise.
With this 16-bit output mode, you don't have to worry about this problem. Thanks!
Cheers,
Fadi
Hi Hayashi,
The ADC is a 10-bit ADC. So if you sample at 125MSPS, your first Nyquist zone is up to 62.5MHz. If you look at the ADC SNR it will be close to perfect for 10-bit. Now, imagine if you are interested in a signal at 10MHz. You can implement a filter that removes the upper half of the Nyquist zone (decimation by 2). Now, your BW is from 0Hz to 31.25MHz. However, since you reduced the BW in half, half of the noise power is gone (assuming the noise is uniformly distributed) and SNR improves by 3dB.
We can actually do this process digitally. If you digitally filter you can get improvement in SNR (better resolution) but less BW. See here from the datasheet:
This is why you can get better SNR than 10-bit. Thanks!
Cheers,
Fadi
