A system-on-chip (SoC) takes an entire electronic or computer system and integrates them into one circuit. By including both the hardware and software, SoC uses less power, has better performance, requires less space, and is more reliable than multichip systems. This makes them highly suitable for Internet of Things (IoT) applications, as they conserve both space and energy.
The type of SoC in this study, the PLSense PLS10, is a prototype microcontroller designed for IoT battery-operated systems that runs at ultralow power to enable it to use lower capacity batteries, or extend the lifetime when using standard batteries.
The lower voltage in such a system means it is more vulnerable to a type of failure caused by radiation, known as a single event effect, where a bit can flip from a “1" to a “0" or vice versa. These can be caused by alpha particles emitted from the chips themselves, or by neutrons produced by cosmic rays.
The ChipIr instrument at ISIS is designed to replicate atmospheric neutron radiation. By testing the resilience of the PLS10 using both ChipIr and an alpha radiation source, the researchers found that the device is more sensitive to “0" → “1" upsets than to “1" → “0" upsets, and that this was particularly true in the case of neutron exposure. These differences were even greater for multiple bit upsets, i.e. several upsets which occurred in the same word. This type of multiple error is more difficult to handle than a single bit upset, as it requires more complex error detection and correction codes. The researchers associated these differences in upset sensitivities to the asymmetry of the logic states in the cell.
To determine whether a SoC was more vulnerable than standard electronics chips, the researchers also carried out the same testing on a conventional device. Their results showed that the sensitivity of the SoC was similar to that of the conventional device, even though that was designed to run at a higher voltage.
Using ChipIr neutron flux which mimics atmospheric neutron flux and is also 109 times higher, enabled the accelerated tests of the ultralow power SOC, and will promote further studies of neutron effects on modern electronics.
The paper is an outcome of the Italian ISIS@MACH collaboration and was highlighted in the IEEE Transactions on Nuclear Science as a feature article.
The full paper can be found online at DOI: 10.1109/TNS.2021.3112622