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https://designers-guide.org/forum/YaBB.pl Measurements >> RF Measurements >> Input Referred Noise of Pipeline ADC https://designers-guide.org/forum/YaBB.pl?num=1232729064 Message started by Scott on Jan 23rd, 2009, 8:44am |
Title: Input Referred Noise of Pipeline ADC Post by Scott on Jan 23rd, 2009, 8:44am I am trying to match lab measurement of short circuit noise for my pipeline ADC. In order to accomplish this, I set up a PSS/PNOISE/PAC analysis for the first 3 MDAC stages and the S/H stage of the pipeline. I set PSS to have a beat F=fs/4. This appears to work fairly well, but I have a couple questions. First, the PAC predicts a 6dB voltage attenuation across the S/H. Is this expected? The S/H does have a return to VCM forced during the sample stage by shorting the S/H positive and negative outputs. In the simulation I have 3 MDAC stages with a 2X gain per stage, resulting in a 8X gain from the output of the 3rd MDAC to the output of the S/H. Referring the noise at the MDAC output to the S/H input is easy (divide by 8), but when referring to the S/H input (to match the lab data) should I include the 6dB attenuation of the S/H? Thanks, Scott |
Title: Re: Input Referred Noise of Pipeline ADC Post by Ken Kundert on Jan 23rd, 2009, 10:58am Does the output of you S/H have a 50% duty cycle? -Ken |
Title: Re: Input Referred Noise of Pipeline ADC Post by Scott on Jan 23rd, 2009, 1:00pm Yes, The output is very nearly 50% duty cycle. |
Title: Re: Input Referred Noise of Pipeline ADC Post by Ken Kundert on Jan 23rd, 2009, 1:52pm There you go. That is your 6db. The size of the Fourier coefficient for a sine wave with 50% duty cycle is half the size of one with the same amplitude that has 100% duty cycle. |
Title: Re: Input Referred Noise of Pipeline ADC Post by Scott on Jan 26th, 2009, 12:51pm Thanks, that's what I thought. It also corresponds with the pnoise analysis showing 6dB higher when I use the time domain analysis as opposed to the sources analysis. Scott |
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