AD7768 Noise Floor

Hi, 

The noise level will depends on the selected power mode, filter type and ODR. The noise numbers in the table is based on the rms value when the inputs are shorted. So changing the reference voltage will not have significant effect. However, like you said lowering the voltage reference will degrade the Dynamic range or the resolution of the ADC. So it is actually the dynamic range or actual resolution that is being affected by the reference voltage value. 

Thanks,

Jellenie

So this noise is totally independent from quantization noise, which would depend on the reference voltage, right?

Yes for high resolution ADCs such as Sigma Delta ADCs the quantization noise is insignificant due to its inherently oversampling technique. So the ADC noise is primarily dominated by input reffered noise or internal noise (i.e. thermal noise, etc.) So for this a higher reference voltage increases the dynamic range (SNR) and increasing the effective resolution. 

I think for lower resolution ADCs wherein quantization noise is the dominating noise the noise level can be reduced by reducing the reference voltage as the LSB size will be reduced.

Thanks,

Jellenie

Yes for high resolution ADCs such as Sigma Delta ADCs the quantization noise is insignificant due to its inherently oversampling technique. So the ADC noise is primarily dominated by input reffered noise or internal noise (i.e. thermal noise, etc.) So for this a higher reference voltage increases the dynamic range (SNR) and increasing the effective resolution. 

I think for lower resolution ADCs wherein quantization noise is the dominating noise the noise level can be reduced by reducing the reference voltage as the LSB size will be reduced.

Thanks,

Jellenie