Design Article
ADC Guide, Part 1: the ideal analog/digital converter
Sachin Gupta and Akshay Phatak, Cypress Semiconductor Corp.
1/2/2012 10:24 PM EST
Analog-to-digital converters (ADCs) are one of the most commonly used blocks in embedded systems. Applications of ADCs include current sensing, motor control, temperature sensing and a myriad of others. As a consequence, understanding the basic specifications of an ADC and selecting an appropriate device for the given application is a must for reliable operation and cost-effective design.
This series of articles will begin with the basics of ADCs, and then discuss different characteristics of an ADC that are important to design, including the impact of various irregularities, types of ADCs available on the market, advantages and disadvantages of each type, and how their selection varies from application to application. This first part of this article series discusses what exactly an ADC is and how an ideal ADC works. In the subsequent articles, we will go to more practical aspects and parameters of an ADC.
To read Part 1 of the series, which is presented as a pdf document, click here.
Sachin Gupta is a Senior Applications Engineer in the Global Applications team at Cypress Semiconductor Corp. He can be reached at sgup@cypress.com .
Akshay Phatak is an Applications Engineer with Cypress Semiconductor. He holds a Bachelor's degree in Electronics and Telecommunications form College of Engineering, Pune (India). He likes to work on mixed-signal embedded systems. He can be reached at akay@cypress.com.
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mngardon
1/4/2012 10:41 AM EST
Very good article on the finer points of ADCs. One issue that I have is that the article is still implies tradeoffs between different external component ADCs. For the applications mentioned: current, temperature, motor control, embedded designers using FPGAs or any other digital circuitry can purchase an IP block that is customized to the application, and embed it directly on the FPGA. Stellamar offers these cores and have implemented them in several high reliability space products, in both FPGAs and ASICs.
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Sachin Gupta
1/6/2012 3:12 AM EST
Hi, Thanks for inputs! I believe all these parameters equally apply for all the ADCs does not matter if it is external or internal to an SoC/FPGA. Still a system designer needs to understand all these things. For example there are SoCs which have different kind of ADCs embedded on the chip and user can select one of those. They need to make a call on which one to be used. Of course, that they need to decide based on the application. For example, even if an ADC support 20 bit resolution available in chip, user may not want to use that much resolution because it will limit the sample rate/ time to sample and hence more power consumption for each sample. We will go in more details on each point in up coming parts of this series.
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Joseph.Haas
1/4/2012 2:43 PM EST
They need to re-check equation 3...there appears to be a typo in the intermediate step.
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Sachin Gupta
1/6/2012 3:36 AM EST
Yes. Thanks for pointing it out this typo. In step 2, it had to be 20 log10 [ 2^N/ sqrt(2/3)].
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