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basic question on sigma delta ADC (Read 3156 times)

manodipan

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basic question on sigma delta ADC
Mar 18^th, 2009, 4:49am

Hi all,
I am just trying to understand switched capacitor type sigma delta ADC....let us say for example we have input sinusoid of common mode=0.6V and amplitude=0.3V with supply 1.2V....now the integrator's o/p range also is suppose 0.3 to 0.9V..now the o/p is either 1.2V or 0V based on the logic and fedback ..here is my question what value of reference(1.2V and 0V or 0.9V and 0.3V) should be chosen for DAC where my input FS=0.6V from 0.3V to 0.9V....
thanks for your help....

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subgold Community Member Offline Posts: 97	Re: basic question on sigma delta ADC Reply #1 - Mar 18^th, 2009, 12:42pm i think it depends on the modulator gain. in another word, the ratio of the capacitor value between the sample path and the feedback path from the dac.
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manodipan Community Member Offline Posts: 83	Re: basic question on sigma delta ADC Reply #2 - Mar 21^st, 2009, 2:18am Hi , thanks for ur reply......i think considering the extreme voltages that circuit can operate as reference we have to get the coefficients and select the cap sizes...
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cmos.analogvala Community Member Offline Posts: 65 India	Re: basic question on sigma delta ADC Reply #3 - Apr 23^rd, 2009, 1:58am I think DAC should be bipolar and VREFP should be 0.9 and VREFN should be 0.3. Am I correct ?
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manodipan Community Member Offline Posts: 83	Re: basic question on sigma delta ADC Reply #4 - Apr 23^rd, 2009, 6:54am Hi , I think you are right ,otherwise opamp o/p goes outside it's operating range.....now problem is that we need to generate two extra voltage references Vrefp and Vrefm....
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