Processing ADC digital output

Dear threenca,

threenca said:

need to test a SAR ADC in ADE Explorer. For an analog input (such as a sinewave) it gives in output a digital bit stream. How can I process this signal/data? I have to obtain the typical staircase signal in order to measure INL/DNL.
Is there any embeddeed fuction in Cadence to this aim?

I am not sure if you have had time to search the Cadence On-line support site, but there is a wealth of information concerning the characterization of an ADC and DAC. Many ADC parameters are included that are far more extensive than simply INL or DNL of a single input sine wave. In fact, I would highly recommend you consider applying more than a single input tone that are at different frequencies (non-integer related). The use of multiple tones will produce intermodulation products whose magnitude will be a direct function of the linearity of your ADC. A single tone input will not provide a good assessment of its linearity with input signals with multiple tones.

Examples of some analyses and parameters, such as SINAD for the ADC, are detailed in the Rapid Adoption Kit (RAK) at URL:

support.cadence.com/.../ArticleAttachmentPortal

There are a series of videos that might also be helpful based on the RAK at URL:

support.cadence.com/.../ArticleAttachmentPortal

You might also consider following your ADC output with an ideal DAC and re-create an analog output. This output cna be directly compared to the ideal analog input applied to your ADC in both the time and frequency domains.

The article entitled "How to plot SFDR, ENOB, SINAD, INL, THD and other parameters for a DAC?" at URL:

support.cadence.com/.../ArticleAttachmentPortal

suggests for static DNL and INL measurements, copying the adc_dnl_8bit and adc_inl_8bit measurement modules from the ahdlLib and editing them for the number of bits that you need (see Figure 1).

Finally, there is a built in INL and DNL function in ViVA (and Calculator). It is described in the ViVA manual at URL:

https://support.cadence.com/apex/techpubDocViewerPage?xmlName=vivaxlug.xml&title=Virtuoso%20Visualization%20and%20Analysis%20XL%20User%20Guide%20--%20Calculator%20Functions%20-%20inl&hash=pgfId-1172167&c_version=ICADVM20.1&path=vivaxlug/vivaxlugICADVM20.1/appD.html#pgfId-1172167

threenca said:

Or is there a way to store data in a file and plot in MatLab?

Yes. You could access the data directly from a ViVA plot to save it to a file or write an ocean script to access the data.

I hope this helps threenca,

Shawn

Figure 1

Shawn

Thank you a lot, Shawn.

Unfortunately, I am not able to access to online Cadence support because I have not Host ID or Reference Key. 

I am a student and a Cadence newbie, sorry for that. How can I find these keys?

Thank you again for your time :)

Dear threenca,

threenca said:

Unfortunately, I am not able to access to online Cadence support because I have not Host ID or Reference Key. 

I am sorry to read that! I think you will need to speak with the individual(s) who administers your Cadence installation to help you set up a Cadence support account. Alternatively, if you know your Cadence installation directory (usually has a name $CDSHOME or something similar...use the UNIX "env" command to query the environmental variable names on your system), then as an example, the ViVA user manualsI referenced may be found at:

<install_directory>/doc/vivaxlug/vivaxlug.pdf

I hope you can find what you need locally or can open a Cadence account to allow you to access the documentation on line.

Shawn