ADC Performance

[panson_hk]

I studied performance of PCM1804 and AK5385 ADCs. Both ADCs claim SNR better than 110 dB and THD less than -100 dB. When I read their evaluation board document, I realized the numbers were obtained with rather high input signal level (over 9 Vpp). In practice, we do use such high-level line signal. Is such high level an industrial standard or just marketing preferred number?

 

[abraxalito]

I'd say its a sign that the input noise of the ADC is significant and the SNR figures can only be obtained with that high level signal. Nothing wrong with that, its not an industrial standard as far as I'm aware. ADCs generally need buffers prior to them because their input impedances are often 'difficult' - include some gain in your buffer if your signal's not 9Vp-p.

 

[jcx]

pro audio studio equipment often specs +24 dBu max for analog levels ~ 12.3 Vrms or nearly +/- 18 Vpk

some industrial sensor/control systems have used 0-10 V or +/-10 V full scale

 

[panson_hk]

I'd say its a sign that the input noise of the ADC is significant and the SNR figures can only be obtained with that high level signal. Nothing wrong with that, its not an industrial standard as far as I'm aware. ADCs generally need buffers prior to them because their input impedances are often 'difficult' - include some gain in your buffer if your signal's not 9Vp-p.

I think we need to take a balance. Front-end amplifier degrades incoming SNR, but prepares the signal ready for ADC to get good performance.