Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines.
Dec 4th, 2020, 3:14am
 Pages: 1
 How to calculate a resolution of a delta-sigma ADC? (Read 2291 times)
 CHL New Member Offline Posts: 3 How to calculate a resolution of a delta-sigma ADC? Mar 12th, 2015, 3:12pm   HelloI'm confused how to calculate the resolution.2^N clock cycles must be counted in order to achieve N-bit effective resolution.For example, averaging 4 samples gives 2 bits of resolution, while averaging 8 samples yields 3 bits.If the output is 00110011...., the 3bit signal is (0+0+1+1+0+0+1+1)/(2^3) = 4/8 = 1/2, whose binary code is '100'.However, I cannot understand the required frequency.If the input frequency is 10kHz and the ADC provides 16bit output, the sampling frequency should be 2*10k*2^16 = 1,310,720,000 HzThis looks like reasonable, but weird.What is wrong with my calculation? Back to top IP Logged
 sheldon Community Fellow Offline Posts: 751 Re: How to calculate a resolution of a delta-sigma ADC? Reply #1 - Mar 12th, 2015, 5:22pm   CHL,   You are averaging the results. This is equivalent to oversampling with a Nyquist rate converter and the rate of improvement fromoversampling is 1/2 bit for 2x sampling rate increase. Delta Sigmamodulator performance is more complex. Getting access to a good textbook would be useful. I like Scheier & Temes "Understanding Delta-Sigma Data Converters"*. It is well written and easy to understand. The equation you are looking for is (1.10), the in-band noise quantization power is   (qrms)^2 = (pi^(2 *  L) * (erms)^2) / ( 2 * L + 1) * (OSR)^(2*L+1)where      L is the order of the loop filter      OSR is the oversampling ratiothe chart in 1.7 shows the in band power vs order of the modulator for oversampling ratios up to 2^10, you can extrapolate from there.This equation is only accounts for the effect of oversampling and filter order on quantization noise. You will still need to account for the effect of  integrator saturation, integrator leakage, jitter, etc. on dynamic range.                                                                      Sheldon* You can find more info by clicking on the books link. Back to top IP Logged
 CHL New Member Offline Posts: 3 Re: How to calculate a resolution of a delta-sigma ADC? Reply #2 - Mar 16th, 2015, 9:09pm   Thank youI will take a look at the book Back to top IP Logged
 Pages: 1