Q&A


Have any ADC/DAC-related question that you think the blog owner or your fellow blog readers could help you answer? The questions can be as basic or complex as you wish. For example:

– “I’m designing a wireless application for the first time. Where can I read more about sampling jitter? How do I know what jitter spec I should be looking for?

– “I’m given the task to choose a suitable architecture for an embedded ADC with specifications X, Y, Z, and I’m thinking about using a pipeline. Should I use a 1-b, 1.5-b or multi-bit/stage architecture, or perhaps not use a pipeline at all? Any suggestions?

Post your questions as a comment here, and hope for the best.

20 responses to “Q&A

  1. Why the $3B data converter market is dominated by the six US companies: ADI, TI, Maxim, LinearTech, National Semi and Intersil. Have any one heard of any data converter companies out of the US?

  2. Good question, Steve. I think it deserves a post of its own. I’ll put one out in a few minutes, and we can continue the discussion there.

  3. Pingback: Reader question: Why is the data converter market dominated by six US companies? | Converter Passion

  4. What is an ADC?

    There can probably be some consensus on a short answer: “Something to convert an analog input into a digital output”.

    How about a long answer? Who would like to share his opinion? 😉

    Accuracy
    – Is a standard digital flip-flop in fact a very low power 1-bit ADC?
    – Is it okay to use external calibration to improve an ADC’s accuracy? And if a PC performs the actual correction, does that make the PC part of the ADC?

    References & supplies
    – Is 0 dB power supply rejection sufficient? 10 dB? 50 dB?
    – How many reference voltages can I use? I would like 2^N of them!
    – Is it okay to use a reference clock? At a higher frequency than the actual sample rate?

  5. Pingback: Reader question: What is an ADC? | Converter Passion

  6. Very good question, Michiel.

    NB everyone: I have given this question a dedicated post, so post all your comments there:

    https://converterpassion.wordpress.com/2011/04/14/reader-question-what-is-an-adc/

  7. Hi Dr. Jonsson, I am wondering the following things in general about the ADC industry:

    –Are folding amplifiers a new concept? Why when I look at the TI website, for example, they do not sell any ADCs with a folding amplifier architecture?
    –How open are the big houses to outside designs? If a small design house comes up with someone innovative, do the big houses adopt, buy-out, or ignore the small houses?
    –What is the main difference between academic specs and industrial specs? How would I “convert” between the two? It seems like when I read academic papers, they claim high speeds at a certain bitrate, but industrial numbers all seem a bit more conversative (i.e. MSPS rather than GSPS).

  8. Pingback: Reader question(s): Novelty of folding amplifier ADC architecture, big houses approach to external innovations, and academic vs. commercial specs | Converter Passion

  9. Hi Bengt,

    After being lost in the world of Converters for a while, I always have this fundamental question as follows:-

    Industries, Publications always talk about GSamples/sec of an ADC or a DAC and the higher the rate, better the converter is. But very few talk about the Bandwidth in the title of the ADC. Even in publications, I always see the title as ” An XGsamples/sec ADC” where as I think it should be “An X Gsamples/sec Y Mhz BW ADC” since many of these converters do not retain performance upto Nyquist.

    Even when looking at the TI ADC’s I need to search the data sheet to find the real bandwidth of the ADC. Shouldnt the sample rate and BW be always reported together so that one quickly understands what the capabilities of the ADC are?

    Could you comment on this?

    Thanks,
    Ameya

  10. Pingback: Reader question: Shouldn’t the (effective) bandwidth of the ADC or DAC also be reported in the titles? | Converter Passion

  11. Pingback: Reader question: Shouldn’t the (effective) bandwidth of the ADC or DAC also be reported in the titles? | Converter Passion

  12. Dear Converter Passion,

    Recently, I have had a question in my mind about DAC performance metrics. While reading many papers about this, I noticed that some DAC publications talk only about SFDR (linearity) in their papers while some DAC papers talk only about SNDR (ENOB) of the DAC. And these papers are all journal papers.

    So my question, how do I do a fair comparison between two DAC’s if one talks about SNDR and one only SFDR. I understand that this would depend on the application, but I have not found any literature which talks about this so far. Could you comment on this?

    /Ameya

  13. @Ameya: Short answer now, but I intend to come back to this topic as you’re touching on the broader subject of scientific reporting practices here – something I think is very important.

    Short: You can’t.

    It’s like comparing apples with fried eggs (not pears because they are too similar). Which leads us to the bigger question: How should you properly report the measured performance of an ADC/DAC in a paper? Short answer there is in my opinion “As fully as possible”. Certainly both SFDR and SNDR should be included.

    Within a week or so, I hope to bring this to a dedicated post so we can continue the discussion there, and I’ll give some more details.

  14. Ameya Bhide

    Dear Converter Passion,

    Thanks a lot for your response. I was also thinking that as the DAC bandwidth increases, the number of noise bins in the spectrum also increase as opposed to maybe 2-3 bins that actually contain the in-band distortion component. So I was thinking that quoting the SNDR is also important in the publication.

    However, I am a novice in the field of DAC’s and that was the reason for the previous question. I sometimes find it very difficult to compare the state of art DAC’s due to my inexperience. Some of the posts on the blog have really helped me get a feel of converters.

    /Ameya

    • Glad the blog is of some help. You can continue to post questions. There are many skilled data converter professionals following the blog, so the chance of someone being able to answer tricky questions is quite high (although for the really tricky stuff, they may want to keep some answers to themselves of course).

      Also, the big companies have some very good application notes. I’ve mainly used app notes from Analog Devices and Maxim myself, but I’d guess that the others are just as good. Some explain the basics of data conversion very well, and others go into specific details. Eventually I might post a list of recommended app notes and other reading.

  15. I am trying to identify market leaders within the time-to-digital converter market and was hoping that someone may be able to point me in the right direction. Is anyone familiar with this topic? I would be very appreciative of any sources or insight!

    • Good question, Kristen. I have to admit I don’t really know the TDC market very well yet, so I’ll leave this question open for others to answer. I know there are some followers of this blog that are more TDC-oriented. Hopefully they can give you good suggestions of such companies. /Bengt

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