Hi,
Could you please tell me what is the 1/f noise corner frequency of the ADC ? I couldn't find it in the data sheet.
BR,
Nicolas
AD9689
Recommended for New Designs
The AD9689 is a dual, 14-bit, 2.0 GSPS/2.6 GSPS analog-to-digital converter (ADC). The device has an on-chip buffer and a sample-and-hold circuit designed...
Datasheet
AD9689 on Analog.com
Hi,
Could you please tell me what is the 1/f noise corner frequency of the ADC ? I couldn't find it in the data sheet.
BR,
Nicolas
Hi Guarana,
Thanks for your interest in AD9689.
The device does not have 1/f noise corner frequency is because it is not considered anymore in testing the device's total noise due to the domination of broadband noise in high-speed ADCs like AD9689.
Regards,
Xavier
Hello Xavier,
Ok, you don't measure it but AD9689 has 1/f noise even if you don't consider useful to test it.
I don't ask you to measure it, just give me an estimate based on a simulation.
Is this possible?
Regards,
N.
Hi Guarana,
I will ask our design team if they have simulations for this test.
Can I ask what is the application or motivation of finding the 1/f corner frequency? What is your target sampling frequency?
Thank you and regards,
Xavier
Hi Xavier,
We do very long acquisitions (300us) with the AD9689 at 2GS/s.
Without signal, RMS noise is OK but peak-to-peak noise is much larger than expected. We would like to understand if the 1/f noise could be the reason of this.
Thank you and regards,
Nicolas
Hi Nicolas,
Can I ask for the waveform capture of your analog input and the FFT waveform? It would also be helpful to know the analog front-end schematic.
Thank you and regards,
Xavier
Hi Xavier,
We don't do any fft on the noise.
We record (524288 samples @ 2GS/s = 262us) We observe a noise ratio (pkpk to rms of 10) instead of 6.
The front-end we use is a SiGe fully diff amp exhibiting very low 1/f noise corner.
Thank you and regards.
Nicolas
Hi Nicolas,
Oh I see. I am now getting picture of where the 1/f noise came.
Can your share your noise measurement and also the fully diff-amp + AD9689 schematic? What is the device name of the fully diff-amp?
Thank you and regards,
Xavier
Hi Xavier,
Sorry but I cannot share the schematic on this site.
The fully diff amp is a full custom design.
My question is very simple. What is the 1/f corner frequency of the AD9689 input referred noise? Just consider the AD9689 on its own with 100 Ohm diff connected between IN+ and IN-.
Thanks and regards.
N.
Hi Xavier,
Sorry but I cannot share the schematic on this site.
The fully diff amp is a full custom design.
My question is very simple. What is the 1/f corner frequency of the AD9689 input referred noise? Just consider the AD9689 on its own with 100 Ohm diff connected between IN+ and IN-.
Thanks and regards.
N.
Hi Nicolas,
1/f noise has normal distribution too, so what you have found is not an indicator of the presence of 1/f noise.
I think the problem can be with the interpretation of the peak-to-peak value, although I do not know how you have determined it.
6 RMS means that on average 99,73% of the samples fall in this range. Taking your case, you have 524288 samples, so you can easily have more than 1400 samples outside the 6 RMS range and therefore have larger peak-to-peak value. Using a normal distribution calculator I’ve found, that at 9.5 RMS you can still have typically 1 sample out of this range (due to statistics it can be more or less of course). This seems to fit your observation quite well.
I agree with that if you are interested in the frequency dependence of the noise, you should use spectral analysis (FFT) and the analog front end can affect the results.
I hope I could help.
Zoltan
Hi Zoltan and Xavier,
Thank you for your relevant input.
I should have done the calculation, sorry it is my fault.
It's true that with such a large record, it's easy to fall out of the +/- 3 sugna.
Thanks a lot and regards,
N.