Sunday, March 29, 2009

New materials and devices

Research on graphene devices continues at a nice rate:

[...] Palacios estimated that it will take as long as two years to demonstrate wafer-scale fabrication of the graphene circuitry.

Although with all these advances, there's a need to more skepticism.

Camera Interfaces

Two articles at the Advanced Imaging magazine sing the praises of different camera interfaces.

Meanwhile, some people take a more critical look at the new USB 3.0 standard.

Power

It's becoming more and more clear that there is a push (at least in the U.S.) to make the power grid a driver for semiconductor business. These last couple of weeks have seen more coverage, research and industry efforts in the "smart grid" arena.

Meanwhile, the field of energy harvesting keeps on gaining momentum.

Tuesday, March 24, 2009

Patents, history and the origins of the CMOS image sensor

Techon reports about the patent fights of Caltech regarding fundamental technologies in the area of CMOS imagers. Without knowing the details, it's difficult to form an opinion on the rightness and/or rightneousness of the lawsuit. Nevertheless, the claim done in the article is that Hitachi invented the (passive) CMOS sensor. Without entering to discuss that claim, the first information on a silicon array image sensor I have comes from the thesis of a student of professor Theuwissen, which reports the first silicon sensor being published in 1966 in a paper by M.A. Schuster and G. Strull: "A monolithic mosaic of photon sensors for solid state imaging applications", IEEE Transactions on Electron Devices, vol. ED-13, pp. 907-912, 1966. The abstract reads:

Monolithic silicon mosaics of photosensor elements have been developed for solid-state imaging applications. The physical structure, design considerations, and performance characteristics of these electrooptical devices as applied to image converter applications are discussed.

The sensing monolith consists of a square 50 by 50 mosaic of phototransistor elements on 0.010 inch centers which are interconnected both by internally diffused strips and by vapor deposited surface bars. Fifty X and fifty Y external leads provide access to any individual element Xb Ya, of the mosaic. Fabrication of this 2500 element mosaic involves the techniques of planar passivation, epitaxial growth, solid-state diffusion, and thin-film vacuum evaporation.

A discussion of sensor operation includes mechanisms of phototransistor action, electrooptical conversion efficiency, and element-to-element crosstalk minimization.

An evaluation of the electrooptical transfer characteristics of the mosaic sensor elements are presented. Uniformity of element response
is typically better than 85% for response within a 3 : 1 range and 75% for response within a 2 : 1 range. Several shades of gray can be imaged simultaneously. The mosaic dynamic range extends over 3.5 orders of incident illumination energy or five orders of output photocurrent. The minimum and maximum detectable signals are approximately 10.0 nW and 1.0 mW, respectively. Sensitivity is of the order of 10^2 to 10^8 microA/mW in the linear portion of the transfer curve.

Incidentally, these two researchers worked at the time for NASA, at which JPL lab the active pixel sensor (APS) was invented about 24 years later. The patents that CalTech owns are from NASA's JPL.

It's a tricky thing to mix patent litigation with engineering history, and I find the Techon article referenced above very disappointing in this respect. I also sense a bit of nationalism in the thesis that Hitachi started it all, but that's just me.

Sunday, March 15, 2009

Miscellaneous articles

Focus on power

As an introduction to the ESC conference, this article introduces energy harvesting.

The main issue will not be as much how to generate energy, but how to deliver it without problems to the circuits that need it. In this direction, a colleague of mine presented her PhD work recently. You can get her thesis here: "Power Management Circuits for Power Generators".

.........

Here is a nice intro to switching power supply design.

Here is another one on power supply cycling to reduce consumption in CPLD designs.

A good introductory tutorial to power MOSFETs.

And another one on Power-over-Ethernet designs.

.........

This post does a good job of looking into the recent Lithium ion battery developments from MIT.

And to finish, a look at renewable energy production and storage at Scientific American.

More on black silicon

More figures and photos on this article at SPIE. Previously...

3D packaging special issue of the Proceedings of the IEEE

A good look at the many faces of 3D IC packaging in the January 2009 issue of the Proceedings of the IEEE.

Sunday, March 8, 2009

PCB design tips

Open source cameras

I posted recently about an open source camera. But there are more out there. The ones from Elphel look good.

Measuring

Being in the lab testing a new system I designed or heped design, is one of the things I like more of this work. A few links to measurement topics:

Sunday, March 1, 2009

New materials and devices

A reversible diode.

A material which draws energy from any mechanical motion.

Oscillators

A very nice article by Paul Rako on oscillators.

RF

Reverse-engineering the first GSM/GPRS CMOS power amplifier.

An article on direct conversion receiver designs.

A tutorial on sampling of band-pass signals.

Sensors

Interesting article on EETimes on MEMS accelerometers.

A Tech Brief on a MEMS directional sound sensor based on the hearing organ of a fly.

A brief on a "High-throughput, on-chip, whole-animal screening at subcellular resolution".

And another brief on "Noninvasive mail inspection using terahertz radiation".

Energy

Different posts appeared during this week with a theme in common. Guess which.

Sensor conditioning circuits

A couple of articles from Planet Analog: