Hi,

if the input of the adc 9653 is shorten, the 3 smallest bits randomly flip. Where does this happen in the adc? I wonder wether I could apply a signal to the adc input. The maximum signal's amplitude is smaller than the LSB/2 . Finally, I can see the signal at the adc output with an fft? Simply, will the signal come through the adc?

Kind regards,

DeeCee

Hey DeeCee,

the AD9653 is a 16-bit converter. The bottom three bits are correlated to the input signal, but are less correlated than say the adjacent three bits.

Another way to think about it is that an ideal 16-bit ADC should have an SNR of around 6.02 * 16 + 1.76 = 98.08 dB. The AD9653 is around 76.5 dB. If every bit is worth 6.02 dB and 98.08 - 76.5 = 21.58 then 21.58 / 6.02 = 3.6 bits of

noise > signal(interpret this loosely). So three noisy bits normal behavior.I answered a very similar question here. Let me know if this helps.

-Tom