  Forum Pages: 1 How to calculate a resolution of a delta-sigma ADC? (Read 2287 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