How to simulate the ENOB of a SAR ADC

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howardtang85

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Does anyone know how to simulate the ENOB of a Charge Redistribution SAR ADC based on cadence spectre simulator?

Thanks!
 

Hi!

You need to do a transient simulation and apply FFT in your output sine wave. After this, you can calculate the SINAD, and consequently ENOB, based on the following relation:


You apply a input sine wave at the input of your ADC, and then, you can use an ideal DAC (for instance, described in verilog-A) to convert your output bits to a sine wave. Then, you do the FFT of your curve. Save your points, and in a excel spreadsheet, you can calculate the SINAD. After this, the using the above equation, you find the ENOB.
 
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Thanks for the solution!

In addition, may I know the ideal DAC should have an ideal transformation characteristic (eg. 1 V using 10-bit, so each LSB will be 1/1024), or same as the ideal transformation characteristic given by the ADC (assume there's a known gain or offset error in the ADC)?
 

I think the ideal DACs from the VLOGA or AHDL libs have a fullscale settable parameter. If not, you can always convert the analog value via a vcvs source from analogLib (sources).
 

Hi howardtang85,

If I undertood well your question, It is better that you DAC described in verilog-A acts as IDEAL without anynon-ideality.
 

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