ADS7946 ENOB beyond 100 KHz

Hi John,

Are you running at a 2MHz SCLK? If so, your not running a clock fast enough to read back data fast enough to read back a 1MHz sine wave. With a 2MHz SCLK, your throughput will be on the order of a couple hundred kSPS in which Nyquist limits your input signal that you can record to about 100 to 150kSPS. You will need a faster SCLK to digitize a sine wave of 1MHz.

Regards,

Tony Calabria

Hi Tony,

My mistake, I ment to write we were planning on sampling at 2MSPS.  SCLK is 40 MHz.  Is there any SNR or ENOB information available above 100KHz?

Regards,

John

Hi John,

Is their a specific frequency that you are interested in? 200KHz, 300KHz....

I can run a test with a sine wave of that frequency to try to get you some baseline numbers.

Regards,

Tony Calabria

Hi Tony,

That would be great!  Could you please look at 250 KHz, 500 KHz,  and 750 KHz?

Thanks again,

John

Hi John,

Here is the data I was able to collect for you. There was not a coherent frequency anywhere around 750KHz so there is not a way for me to get an accurate answer for you on that input frequency. I am a little concerned that I was running into the performance of the function generator that we had. I usually use a multiple order band pass filter to help filter the input signal prior to the ADC but we do not have a 250KHz and 500KHz block filter available. 250K and 500K are on the fast end for a 2MSPS data converter but still do show nice results. Keep in mind that at these speeds, the data only records 8 / 4 data samples per sine wave period.

Regards,

Tony Calabria