By Troy Jones, Xilinx
EETimes (October 21, 2021)
Space is easily the most challenging environment for IC designers. Without Earth’s atmosphere to protect them, electronic systems are vulnerable to high-energy (ionizing) radiation including alpha and beta particles, gamma and x-rays as well as galactic cosmic radiation.
Ionizing radiation has enough energy to remove an electron from its orbit. When that electron represents a bit in memory or a value on a bus interface, its value can be changed or “flipped.” Such an event goes by many names including single-event effect (SEE), single-event upset, or single-event latch-up. Regardless of what you call it, if the wrong bit is flipped, such as an instruction in the application code or a control bit in a register, the entire system could fail.
Radiation-tolerant vs. radiation-hardened
To operate in space, electronic systems need protection against radiation-based events. Some IC manufacturers offer “hardened” components such as insulating substrates in place of the standard semiconductor wafer. Hardened ICs are more resistant to radiation-based events but not immune to them. In addition, hardened ICs are significantly more expensive because of their more complex design requirements and lower production volumes.
Among the factors deterring spacecraft designers from choosing hardened ICs is the lag time for a hardened component to enter production if the desired component can even be designed as a hardened IC.
Rather than attempting to prevent ionizing radiation effects through radiation-hardened-by-design methods, designers can instead utilize devices and design techniques intended to detect and correct them when they happen.
This is known as radiation tolerance.
A key advantage of this approach is that many components can be made radiation tolerant. For example, many memory technologies employ error code technology to detect, and correct bit flips in memory.
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