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Going through a mixed-signal SOC design, from A to Z: defining the concept

(Editor's note : we are resuming our “dialogues” between these two distinguished engineers with this special, multipart series on the product development process. This is based on a real-life example and hands-on reality, not speculation or an academic perspective. If you want to see the rest of these dialogues, or other articles by these authors, you'll find a linked list here.)

(Editor's second note : This is Chapter Two of an ongoing series; to read Chapter One , click here.)

[The setting : Dave Ritter has received a rare official meeting notice to join Tamara Schmitz (Dr. T) for an unspecified discussion …]

Tamara Schmitz : Last time, we went through an overview of what goes into making an integrated circuit. If you remember, our list of critical steps included:

  • Product Concept – from marketing (in this case).
  • Technical Feasibility – including prototype.
  • Business Plan – including cost, schedule and potential market data.
  • IC Design – putting together the transistors and simulating the result
  • Test Development– including built-in test
  • Bench Verification – testing the first parts using video test equipment
  • ATE Characterization – testing more of the first parts using automated test equipment
  • Bench/ATE Correlation – making sure the bench tests and ATE agree.
  • Customer Evaluation boards – designed and built by applications
  • Final Data Sheet with specs, curves, and apps section – written by applications
  • Promotion and Support materials – orchestrated by Marcom (Marketing Communications)


Dave Ritter : You took notes!  I’m flattered!

Dr. T : All of our conversations are noteworthy, Dave. This time, I want to understand what goes into each of those steps. Are you ready?

Dave : As a boy scout (a long time ago) our motto was “Be Prepared.” I’m ready!

Dr. T : Great! The first step, and arguably the hardest, is coming up with an idea. You mentioned that your latest video equalizer, MegaQ, was a friendly challenge between marketing engineers and applications engineers. 

Dave : Indeed, MegaQ was cooked up by apps and marketing based on some discrete solutions we had developed over the years. The questions were: could we integrate it, and could we automate it. Oh…and could we make it go a mile. But the ideas can come from anywhere, even an undergraduate summer job.

Dr. T : It sounds like you might have a story to share…

Dave : Yes. It was the project that started my career.

Dr. T : Now Dave, it has to be about electronics, not steam engines!

Dave : It wasn’t that long ago, just the mid-1980’s. I had joined a small company that build video test equipment. They were defining the next “waveform/vectorscope”, a specialized oscilloscope for video systems. It had multiple inputs so you could observe up to three different cameras at the press of a button. The interesting thing was in the definition: the product would display one, and only one, signal at a time because multiple signals would be too confusing to the user. 

Dr. T : Was that a problem?

Dave : It is if you’re a technical director aligning multiple cameras. It turns out that the single most useful thing we added to the product (and we added a lot: first uP controlled monitor, touch panel screen control, etc.) was the ability to overlay three waveforms and three vector displays simultaneously. A camera setup technician could view all critical timing aspects of the cameras on one screen simultaneously, and he could do it while the cameras were ‘on air’. 

Previously he had to do it ahead of time, and use the special effects panel to do the overlay. We got a testimonial from the technical director of a well-known late-night network-news program, thanking us for making his life easier.  

Dr. T : So the idea came from the customer and made a better product …

Dave : Almost. The whole story is that I spent the previous summer working with the local cable TV folks in their small studio. I had to use waveform monitors and vectorscopes to align cameras, and it was a pain because I could only punch up one at a time. So I made sure our new product fixed that problem with it’s ‘triple overlay display’ and that’s why the guy at Nightline liked it so much.

Dr. T : So the idea came because you accidentally had a summer job at the cable company?!?!

Dave : Yep. It’s a mixture of customer requests, competitive products, and accidental summer jobs. No matter where they come from, it’s almost always the result of an interaction with people working in the field. It might be field applications engineers solving customer problems. It could be a conversation at a workshop or even your own cafeteria. Sometimes it is marketing folks analyzing the competition… the list really doesn’t stop.

Dr. T : I assume that ideas develop over time, too.

Dave : Sure. A single customer may have a specific requirement, but we want to serve the whole market. So it makes sense to talk to a lot of potential users and come up with a cool solution that helps them all. That takes time to develop.

Dr. T : What kinds of features do we add to make it useful to multiple customers?

Dave : It could be a whole range of things. It might be programmability for gain or channels. It might mean keeping a component off-chip so the user can set a current level.

Dr. T : What about on MegaQ?

Dave : On MegaQ, we wanted to be able to improve and extend the reach of composite video.  Three main features were added to make it easy to use in a wide variety of applications. The first is that it is an equalizer system that only needs to be installed on the receive end (no need to reconfigure the cameras installed on poles or in far corners of the building). 

Secondly, MegaQ automatically calibrates the equalization for any length of cable from zero to 5,300 feet, to eliminate complex installations. Third, it has an automatic invert feature in case the installer accidently reverses the video input.

Dr. T : Got it. That sounds easy to use and fun challenges to develop. But now let’s get to the business plan—we need to make money. 

Dave : I think you’ve already joined the ranks of management if you are already asking about the money. But let’s look at technical feasibility first. If it’s feasible, then it makes sense to see if we can make money at it.

Dr. T : Of course. Let’s see. I’d want to know how customers are dealing with this problem, what has been done before and what the competition currently offers.

Dave : Sometimes you’ll find that the state of the art is a discrete design. Sometimes it will be a system cobbled together with ICs designed for other applications.  And sometimes we are lucky enough to discover an area where there is no good current solution.

Dr. T : Am I sensing that MegaQ fits in this final category?

Dave : Yes. MegaQ is for analog security video, and it has turned out to be pretty unique. We already had manually adjustable equalizers for other markets, but security people wanted an automatic solution:  plug in the cable and MegaQ would do the rest. The only available monolithic solution had a limited range, but some customers used it with their own added discrete embellishments. Otherwise customers were using discrete solutions, and the most sophisticated had microcontrollers to automate the operation.

Dr. T : Can you sketch an example circuit diagram for the way customers were addressing the problem?

Dave : Sure. They used basic equalization stages like this (Figure 1 ). Such a circuit can use either manual switches, or a microcontroller to control them automatically. Of course automation implies that we have an algorithm to effectively control the equalizer.

 

Figure 1: Block diagram of typical discrete equalizer solution

Dr. T : When you first looked at the current customer solution, did you imagine how many of those components you could include within your monolithic (single IC) solution?

Dave : as many as possible…

Dr. T : Sure, of course. But what are the trade-offs that help the team decide which components to fold into the package and which to leave external?

Dave : That’s a really good question. As the whole state of the art advances, customers expect more and more to be integrated. A really good chip has bypass caps on the supplies and not much else. But in our case it was all about retiring risk. We had a prototype, and we had full-chip simulations, but neither is exactly the same as the chip.

We chose, for example, to use external coupling capacitors to the inputs so that we could handle any DC level without a problem. If these were on-chip, they would have more-limited DC range. The hidden advantage is that the video clamp time constants are now determined by external components.

This was a big help in adjusting the part to high noise environments. In today’s world, we can integrate almost anything, but the two things we balance are cost and risk to make sure we have a saleable product.

Dr. T : That’s clearly the takeaway for today – balancing cost and risk.  That sets us up perfectly for talking about the business plan next time.


About the authors

Dave Ritter grew up outside of Philadelphia in a house that was constantly being embellished with various antennas and random wiring. By the age of 12, his parents refused to enter the basement anymore, for fear of lethal electric shock. He attended Drexel University back when programming required intimate knowledge of keypunch machines. His checkered career wandered through NASA where he developed video-effects machines and real-time disk drives.

Finally seeing the light, he entered the semiconductor industry in the early 90's. Dave has about 20 patents, some of which are actually useful. He has found a home at Intersil Corporation as a principal applications engineer. Eternally youthful and bright of spirit, Dave feels privileged to commit his ideas to paper for the entertainment and education of his soon to be massive readership.


Tamara Schmitz grew up in the Midwest, finding her way west with an acceptance letter to Stanford University. After collecting three EE degrees (BS, MS, and PhD), she taught analog circuits and test-development engineering as an assistant professor at San Jose State University. With 8 years of part-time experience in applications engineering, she joined industry full-time at Intersil Corporation as a principal applications engineer. In twenty years, she hopes to be as eternally youthful as Dave.

Editor's note : If you liked this article and are interested in “analog” issues such as signal input/output (sensors and transducer, real-world I/O);interfacing (level shifting, drivers/receivers); the signal chain, signal processing (op amps, filters, ADCs and DACs); and signal integrity, then go to the Planet Analog home page here for the latest in design, technology, trends, products, and news. Also, sign up for our weekly Planet Analog Newsletter here. You won’t be disappointed, and we won’t waste your time, that's a promise!

1 comment on “Going through a mixed-signal SOC design, from A to Z: defining the concept

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