ADS8689: How to calculate noise floor of a Delta-Sigma Modulator?

Daniel Rios

Part Number: ADS8689

Hello,

I tried using the the SNR specification on the datasheet to solve for the noise floor given SNR = 20log(Vmax/Vnoise). However, I don't think this is accurate. I wanted to know if there was a more "proper" way of doing it.

I want to measure a difference of 76uV and would need to have a noise floor below this value.

Thanks,

Daniel Rios

over 5 years ago

0 Dale Li over 5 years ago

TI__Mastermind 45455 points

Hi Daniel,

Can you please make it clear about Delta-Sigma Modulator? ADS8689 is a SAR ADC.

Thanks&regards,

Dale

0 Daniel Rios over 5 years ago in reply to Dale Li

TI__Prodigy 290 points

My mistake. How do you calculate the noise floor for an ADC? Does it make a difference whether it's a SAR or Delta-Sigma on how you calculate this?

Thanks,

Daniel Rios

0 Dale Li over 5 years ago in reply to Daniel Rios

TI__Mastermind 45455 points

Hi Daniel,

2.5Vref input range(10.24V) as an example, the SNR of ADS8689 is 91dB, so the noise can be calculated:

V_(FSR_rms)=V_FSRpk∙0.707

V_(FSR_rms)=0.5∙FSR∙0.707 =0.5∙10.24V∙0.707=3.62V

V_nADC=V_(FSR_rms)/10^((SNR_ADC/20) ) =3.62V/10^((91dB/20) ) =102μVrms.

I hope this is useful for you.

Regards,

Dale

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ADS8689: How to calculate noise floor of a Delta-Sigma Modulator?