Sensors Will Proliferate In SoCs

As geometries shrink, the ability to monitor what’s going on in a device is increasingly important.


No one likes being put on the spot, and yet we all like a forecast…and as we all know, the only guarantee with a forecast is that it is wrong. Sports commentators have carved out a special niche for themselves with the ‘commentators curse:’ just as they extol the virtues of an individual or a team, the sporting gods prove them wrong in spectacular fashion! Governments are no better: economic forecasts don’t usually hold for more than a quarter, which is what makes Gordon Moore’s prediction all the more impressive.

I’m sure everyone in our industry is familiar with Moore’s Law. While at Fairchild Semiconductor in 1965, Gordon Moore was asked to contribute to the 35th anniversary Electronics Magazine with a prediction for the future of the semiconductor components industry over the next 10 years. His response was, “the number of transistors in a ‘dense IC’ would double every two years.” What a prediction. It was correct for the next 50 years and is only now starting to ‘fade.’

So what has Moore’s Law got to do with Moortec?

Broadly speaking, he predicted that over time transistor density would increase, so more could be put on any one device and predictably devices would grow. This wasn’t really an issue in the early days, when geometries were measured in micrometers. In fact, all the way down to 40nm there weren’t any major issues. It was the transition from planar to finFET technology where things started to change. The bit Gordon wasn’t too explicit on was the change in leakage current as we ride the geometry wave. Leakage current starts to become an issue in finFET and is just plain ugly sub 7nm, add to which the chip sizes grow significantly as the applications of the day try to maximize the benefits of these plentiful transistors.

Ok, big deal…chips get bigger, leakage increases, power density is now also increasing with the ‘end’ of Dennard Scaling. You don’t need to be Nostradamus to predict that things will start to warm up a little. Yet that isn’t the only effect you’ll be seeing. Temperature is a first order effect: as the heat rises so data throughput drops, power consumption increases and so the cycle builds on itself.  Second order effects then come into play: the silicon starts to age, reliability takes a hit and can have knock-on effects into your system reliability and overall performance.

Great man though he was, Gordon didn’t mention any of that.

So here is where Moortec’s Law comes in (just for the record, I’m not claiming it will last 50 years!). ‘The number of sensors used in a ‘dense IC’ will (at least) double per geometry shrink.’ There is a second Law (as with Gordon, he too had a second, less well known Law): ‘the number of sensors used in individual designs will rise exponentially as engineers appreciate the information they can divulge in mission mode.’

The proliferation of sensors in SoCs will not only be driven by better understanding of the value of the data they provide, but also a deeper appreciation of the type of data they can provide in different areas of a design. Imagine baking a soufflé in an oven without a glass door. You are blind to what is happening inside. You’ve followed a recipe and yet you can’t be sure the eggs were a uniform size or the flour was a consistent strength or that the oven holds its temperature evenly throughout the cooking process…until you open the oven door, you don’t know what to expect. Open it too soon and it will sink, too late and it will have burnt!

SoCs are no different, except the cost of failure is many orders of magnitude greater. That ‘mission mode’ visibility the glass door provides is no different from having 10s, 100s or even 1000s of sensors in your device.

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