Interested in energy-efficient SOCs? At the IP-SOC Conference last fall, STMicroelectronics’ Giorgio Cesana presented examples of the technological competitiveness of FD-SOI IP for memories, cores, ultra-low voltage and analog.
Here’s a brief recap. The complete presentation, entitled “FD-SOI Technology for Energy-Efficient SoCs: IP Development Examples” is available on the Design & Reuse website (click here to view it).
Memory is the proverbial canary in the coal mine for chip designers. To run reliably, pairs of transistors can’t be mismatched – and this becomes more critical with the lowering of the supply voltage (Vdd), nowhere more so than in memory. FD-SOI decreases mismatching by 40% compared to low-power (LP) bulk, and decreases leakage by a factor of 8. Soft error rates (SER) are 100x better in FD-SOI than in bulk. And of course, being able to run at lower voltages can make a significant contribution to battery savings in portable devices.
In the example of a dual ARM A9 subsystem architecture, ST’s IP is used to generate programmable body voltages, enabling a CPU to run at 300 MHz with a 0.5V supply voltage. Increasing the supply voltages increases the performance: up to 2.3 GHz at 1V, and on to 3 GHz at 1.34V. And with forward body biasing (FBB), which is only possible in FD-SOI, you get 1GHz at 0.6V when you need it.
Dynamic process scaling, thanks to extended body biasing, allows dynamic switching between high-speed and static-power optimizations. In a multi-core context the effects are dramatic.
Ultra-Low Voltage Apps
For things like medical devices and Internet of Things (IoT) apps, the ultra-low voltage design enabled by FD-SOI should be a key differentiator.
The presentation shows that ST is particularly pleased to emphasize what analog designers can do with FD-SOI. For example, in a switch the resistance ratio between on and off (Ron/Roff) is 10x better in FD-SOI than in bulk or FinFETs. Power signal gains are improved by 6x without using pocket implants, and matching is better in short-channel devices because there is no channel doping.
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