Currently there are just a few chip dissector enthusiasts sharing freely their findings with others. But two-three years ago, we didn't even have a single open chip database. Till this day the two biggest chip die microphotograph databases are zeptobars.ru and siliconpr0n.org. I was browsing around their chip database these days, and I am getting to see lots of inventive design approaches. Sometimes you can clearly identify that some chips have gone through several really messy metal mask fixes, and astonishingly such designs have still been shipped to mass production the way they are.
As the guys from siliconpr0n.org are providing their microphotographs under a creative commons commercial license (wow! even commercial! you guys rock!), I got tempted to use one of their chip photographs to create an infographic, denoting various details around the design. I chose a simple chip, which is a custom 65CX02 microcontroller used in a pocket game (it is not sure which one, tetris maybe?) using 3 Metal and 1 Poly process. It is hard for me to identify the exact process node, however, judging by the bonding pad size my guss is that it is somewhere around 0.8 um CMOS, if not even larger.
My first intention was to stick with red labels only, denoting analog design related details, however, as this chip is almost "purely digital" there is nothing much to comment, which lead to empty gaps. Well, I filled-in the gaps with blue labelling denoting my assumptions on the basic sub-blocks of this microcontroller.
The nicest detail I like about that chip is the tapered star connection at the bottom, which assures minimal noise on the oscillator circuitry, which is pretty much the only analog block in this microcontroller and uses the same digital supply as the rest of the core logic. Here's a zoom:
Some thoughts arose that it is clear — whoever designed this had an idea of what he was doing. Otherwise he could have easily merged the metal rails, it is easier to design it that way, so why bother splitting. Unfortunately it is not a very common scene, seeing pure layout engineers implementing such tricks at every level of abstraction in the design. In the case with this chip, it is kind-of clear that this was a decision taken at a top level.
On the left you can also see split power to the analog blocks as well. What is also interesting is that I can't identify passive ESD diodes for the power rails, what is visible though, is a tiny active ESD protection on top of the chip rail. It might be that parts of it are also circuits assuring correct power-on sequence, or it might be that there is power ESD but I am not seeing it under the metal padding.
I am leaving you now to explore more chips yourself in the databases.
Dear handful of science geeks! As the title suggests, I have finally decided to move on a separate domain. In fact, I should have done that six years ago when I started-up this page as a "joke", which was supposed to be a "just temporary" solution to hosting "stuff" online.
I am very happy to introduce you to transistorized.net although, I am still not extremely delighted with the name I picked some time ago, again as a "joke". But let's not care about names, as time goes I'm sure we'll start liking it better.
And also, please, stop me if I ever decide to start fiddling with these shell scripts and bodge work again! I should've migrated to Wordpress a long time ago, but ahh, you youngsters nowadays... This actually gave me the inspiration for another purely philosophical post on the incremental improvements in EDWARDS... let's see...
P.S. EDWARD = Engineer Doing Wildly Awkward and Recurring Drudge
I have been honoured to be the thesis supervisor of one of our brightest fourth year students, who did an excellent job helping me out with some pad and ESD protection designs last summer. He will be working on column-parallel ADCs, thus, I've decided to put-up a quick introductory summer reading list on SAR ADCs.
One might say that we are flooded with information nowadays for which he may totally be right, however, the field of VLSI design is still kept in secrecy and large data converter systems are often considered a mystery by newcomers. What's most important with introductory books in nieche fields is that they keep the details out of band, but yet try to maintain a colorful backbone such that the reader doesn't get bored. Because nieche field literature is ususally developed by narrow-field specialists, it isn't rare that we see papers unsuitable for undergraduate education. In fact, the greatest knowledge gap in university education is between the under - post graduate studies, hence, to make the climbing slope milder here are my suggestions for the area of image sensor converters.
Perhaps one should start by having a look at Walt Kester's introductory notes on Successive Approximation ADCs - ADC Architectures II: Successive Approximation ADCs.
After examining the fundamentals, I would head the list with a 200+ page PhD thesis by Albert Chang from MIT on "Low-Power High-Performance SAR ADC with Redundancy and Digital Background Calibration". Albert offers excellent introductory chapters (A! LOT!) on the successive approximation algorithm and the digital arithmetic, all of which is presented under the light of actual transistor-level schematics.
One of the earliest reported column-parallel SAR ADCs used in an image sensor lies in Eric Fossum group's paper entitled: "CMOS Active Pixel Sensor with On-Chip Successive Approximation Analog-To-Digital Converter" published in the Journal of Electron Devices, Oct 1997. This paper shall provide you with an insight on actual implementation details and the specifics of the column-parallel capacitor layout of the bridge capacitor DACs.
A more modern and representative paper is: "Low-Power CMOS Image Sensor Based on Column-Parallel Single-Slope/SAR Quantization Scheme" by Tang et al. where they offer a clasisc two-step data conversion using a single-slope for the fist 3 MSBs and an 8-bit SAR scheme for the LSBs respectively.
The reading matetial on this line may be too advanced for a thesis reading, but I am listing it here, as it offers an elegant scheme coping with physical process defects and capacitor mismatch. A Low-Power Pilot-DAC Based Column Parallel 8b SAR ADC With Forward Error Correction for CMOS Image Sensors by Denis Chen from SSIS.
A few extra reading (which you may want to actually start with first) is an application note by Texas Instruments on Understanding Data Converters. There's tons of information on data converter fundamentals online, but I also find these notes from Boris Murmann from Stanford to be very clean: VLSI Data Conversion Circuits. And finally, a nice book edited by some of my friends from Linköping: CMOS Data Converters for Communications by Gustavsson, Mikael, Wikner, J. Jacob, Nianxiong Tan.
There might be more and even better introductory reading material, however, I am sure the provided above would source you with plenty of references, and if you have any suggesstions for more interactive literature don't be shy to use the comments so I can add it up.
How many words do you know ending on tron?
Make yourself a cup of "coffeetron" warmed-up by the magnetron driven by the kenotron in your microwave oven powered and protected by cathodotron in your local power plant. Make yourself comfortable then search for any of these terms and have some fun:
synchrotron; magnetron; thyratron; klystron; klystron; kenotron; electron; neutron; iotatron; cyclotron; cosmotron; dynatron; betatron; audion; pliotron; mesotron; ignitron; strobotron; negatron; antineutron; tevatron; calutron; bevatron; positron...
The etymology of -tron endings come from Ancient Greek, where they have been used as a suffix denoting an instrument. How about the electron? Well, my digestion here is that it is an instrument in the end. Also note how many particle accelerator construction attempts mankind has made. The rest of the majority happens to be electronic tubes, cool! Let me know of your suggestions for expansion of the list? Happy physicsing!
some random thoughts on engineering ethics
Ever had the feeling that all technologies surrounding us are an offspring of the hidden powers of organized crime groups?
In the early 1940s, with the number of great discoveries in 19th century ignited by the second technological revolution a new era was born - the digital revolution. Back in 1947 in his short story "Little Lost Robot", Issac Asimov predicted that technology would have advanced sufficiently by century's end that it would allow for humanity to establish a base on asteroid to perform research on space travel. With the landing of Rosetta last year, Asimov's story as usual held true again. The past 100 years have shown that the engineering disciplines, compared to all other fields of science, have probably by far the highest impact on society. The last is especially true with the emergence of the information age, which gives us one of the most influential instruments for psychological control humanity has ever had. With all that said, engineering science plays an important role in the development of our society, and to a large extent the future of mankind now lies in the hands of engineers.
Now teleporting back to early 1900 in the era of the second industrial revolution. With growing demands for easeing of mankind life by means of industrializaton, engineering established itself as a distinct profession. With the erection of a number of large civil engineering constructions, there had been a series of significant structural failures, including some spectacular bridge engineering disasters. Notably the Tacoma Narrows Bridge collapse and the Ludendorff Bridge disaster. These had a profound effect on engineers and forced the profession to establish some technical and construction practices which were driven beyond anything else but the price of human lives. As a measure, the development of ethical standards was established by an impressive number of world organizations, placing life safety to highest order. I am tempted to quote the engineer's seven canons here, published in the Code of ethics, established by the American Society of Civil Engineers in 1914.
It is here to mention that engineering science constantly faces a number practical trade-offs, which also means that material savings and cost-efficiency are an immense feature of standard consumer engineering. When engineering ethics face the model of modern corporate powers, often, highly exothermic reactions can occur and as is often seen in nature the physically strongest monkeys always win banana fights. Unfortunately strongest does not always mean wisest, in fact, the contrary is usually the case. It means that engineering practice until now needed not only to take care of life safety, but also the corporate wallet. A wallet which vigorously dislikes any kind of drainages. In retrospect, the early established engineering ethics have so far worked quite well in most cases, despite that they are not always obeyed by large enterprises, take the recent case with Volkswagen for example.
Nevertheless, the consequences of such historical disasters may seem like a piece of cake, compared to what disasters of the future information age could be if appropriate measures are not taken. Not surprisingly history tells us that mankind may again fall into the same traps, some of which have been identified as early as 600 BC with the sudden collapse of the Egyptian civilization. The most drastic and rapid social change that mankind has ever experienced actually took place some three thousand years ago! A change from primitive barbarism to a posh civilization (in the context of such a far distant era) till a complete disaster and a vanish of identity. This is all just history, however, process recurrence is something normal in nature, at least to the extent of trusting empirical laws such as Zipf's. This historical de-brief should hint that nowadays engineering science is facing new challenges, unconditionally different from any other kind of past experiences.
During the 80s, coining the term cyber warfare in his novel "Neuromancer", William Gibson successfully pinpointed the soft threats of the information age - data and identity thefts and document forgery. But this was just the beginning, as the power of the Fourth World has reached influential levels in society beyond anything else seen in the past. With all of that said, due to this rate of influence, technology control should be tightened to a whole new order of magnitude - control which now widely lies in the hands of engineering ethics. Although technology provides us with rich possibilities it does not mean we should employ all in all, just because we can. Spying nowadays is a matter of a bit flip - it is needless to say that builders should not always be putting the donkey where the master says. Instead, it is the engineer's responsibility to act professionally and in line with the principles of sustainable development, no matter what the boss says. If each of us acts with merit of honor following certain principles - the collapse of the Fourth World would never happen. If misuse can be prevented in lowest layers of hierarchy, then it'd better be the scientists and engineers; hence some amendments in our code of ethics is needed, in fact we have been in need for it for a long time. Now, I realise that such argument is going to run into immediate objections: "who are you to say what code of ethics is". And on one level, this may obviously be true. However, during my short life experience I have seen a number of engineering ethics misconceptions which are inciting me to think that something is wrong. Another less visible principle delusion which also needs addressing is the modern model of self-induced slavery; what do I mean by that? Example - medical electronics is a field of engineering with a primary aim of making people's lives better, however, nowadays I see the majority of it as monstrous money making machine. How can brain chip implants, pacemakers or disposable endoscopic cameras be sold with nearly a thousand percent (if not even much more) profit margins? Products, the majority of which were developed using public money to start with; and are primarily used in the public sector. All of the above makes what's available today practically inaccessible, or if accessible not without some form of arm-twisting. This is the second, much less obvious threat of our digital revolution requiring more emphasis in the philosophy of science. We should not fall into this trap - getting down, surrendering and rendering what we have discovered into the rulership of some large enterprises represented by single identities.
Having control over mankind's way of thinking, sensing and experiencing information has been by far the most powerful tool scientists have ever held. Such tools combined with the caprice of some corporate maggots can form an explosive substance for humanity. Engineers - always endeavour personal commitment in what you do, amplify your moral principles to highest order and never fall into someone else's plans!