Supplement: Aerospace, Military and Defence
Radiation-tolerant FPGAs offer high reliability and reconfigurability to solve spacecraft design challenges
By Tim Morin, technical fellow, Microchip Technology “
Space, the final frontier.” Spoken by James T. Kirk of the Starship Enterprise during the 1960s television series Star Trek. Television makes it look easy. The reality is quite different. Space is harsh - a vacuum, cold and hot, with cosmic radiation. Then there’s the distance between objects. The vastness of space is mind-boggling. Harshness and distance make autonomy and reliability critical for electrical and mechanical systems. With the renaissance in space that’s occurring coupled with the drive to lower costs, this article will explain some of the different options available to the electrical designer to meet reliability and mission requirements. Field Programmable Gate Arrays (FPGAs) are used extensively in space because: 1. they allow the space engineer to design circuits in such a way as to be resilient to the harshness of space; and 2. There aren’t many space-qualified components in the world for a designer to choose. Two major concerns for designers of space systems are radiation effects and power consumption.
Radiation effects in space
Total Ionizing Dose (TID) is caused by radiation from charged particles and gamma rays in space. This radiation deposits energy by causing ionization in the material. Ionization affects the material’s charge excitation, transport, bonding and decomposition properties. This negatively affects device parameters. TID is the cumulative ionizing radiation that an electronic device receives over a specified period, usually the mission time. Radiation absorbed dose (RAD) expresses the amount of radiation and determines the damage. Depending on the radiation tolerance or TID rating of a device, it may experience functional or parametric failures. TID radiation in FPGAs can cause an increase in propagation delay, which lowers device performance. High TID exposure can also lead to an increase in leakage current. Particle radiation causes Single Event
38 March 2024
Effects (SEEs) like Single Event Upsets (SEUs). Protons, heavy ion and alpha particles can instantly upset or permanently damage transistors, causing logic failures in the system. Depending on the location of the particle impact, the next clock cycle can clear the error. However, it can also cause a Single Event Functional Interrupt which alters the behaviour of the system.
Single Event Latchup (SEL) is a condition that can cause device malfunction due to a high current state caused by a single event. An SEL may or may not be destructive. In a destructive latchup event, the current will not recover to the nominal value. In a non-destructive latchup event, the high-level current will return to the nominal value after power-cycling the FPGA.
Power consumption
Common practices for transferring heat on the ground don’t apply in space. You can’t move air across a heat sink to move heat from a semiconductor into the atmosphere. Heat must be thermally conducted away from the device generating the heat source. Lower power devices reduce the mass required to thermally conduct heat to a cold wall. Lower
Components in Electronics
mass reduces launch costs. The amount of on-board processing requirements for imaging, automation and communication for space satellites, landers and rovers is increasing rapidly. Driving the need for more signal processing, which exacerbates the power problem. The ultimate definition of the “intelligent edge” is these new space systems at the edge of our atmosphere and within our solar system and they all need more processing and lower power at the same time.
Quality
Satellite and spacecraft system designers have a few different options when selecting field programmable gate arrays (FPGA) semiconductors. One FPGA option is commercial off-the-shelf (COTS) components that reduce component unit cost and lead time, but they are generally not reliable enough, must be up screened (which increases cost and engineering resources), and require soft and hard Triple Modular Redundancy (TMR) to mitigate radiation effects in space. In missions where failure is not an option, designers typically choose higher-cost FPGAs that are radiation-hardened by design (RHBD), which are already screened and qualified to
Qualified Manufacturers List (QML) Class Q and V standards. QML Class V is the highest qualification standard for space semiconductors. Manned and safety-critical missions rely on QML-V components to mitigate the risk of failure.
Designers must meet the increasing need for a challenging combination of higher performance and greater on-board data processing and high-speed communications capabilities in space. These radiation- tolerant RT FPGAs provide a solution that is radiation tolerant by design, backed by its manufacturer’s space flight heritage and expertise and with solutions that undergo QML Class V testing. This article examines the different FPGA technologies that are available for space applications, and the process for developing the components.
Comparing FPGA technologies There are four basic types of FPGAs:
SRAM-based FPGAs
SRAM-based FPGA stores logic cells configuration data in static memory. SRAM is volatile and can’t retain the device configuration without power.
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