Chiplet-Based FPGAs Optimize Performance for Space Applications

Field-programmable gate array (FPGA) architectures for space must reconcile computing capacity, reliability, power consumption, and component availability for very long missions. A chiplet-based approach can separate processing and I/O, allowing for the optimization of radiation tolerance, performance, and upgradeability.

Beyond the monolithic FPGA

Space applications require increasingly higher processing capacities, especially in payloads dedicated to Earth observation, scientific data processing, and high-speed communication systems. The FPGA continues to be considered a particularly interesting platform because it allows developers to implement parallel pipelines, hardware accelerators, and reconfigurable interfaces without resorting to a dedicated application-specific IC.

The increase in complexity, however, introduces an architectural problem that is difficult to ignore. Concentrating all functions in a single die means associating performance, interfaces, and the surface exposed to radiation with the same technological process and the same level of qualification. Reliability and radiation tolerance are specific requirements for FPGAs in space, while long development cycles and component availability make full lifecycle management particularly important.

One possible evolution is to adopt a chiplet structure in which the FPGA system is decomposed into multiple specialized dies connected through an advanced package. The goal is not simply to physically divide a monolithic device but to separate functions with different requirements, making the computational logic, memory, interfaces, and service circuits independent, at least in part.

Partitioning compute and I/O to better handle radiation

In a chiplet-oriented platform, the first level of design is functional subdivision. One chiplet might contain the FPGA fabric dedicated to computing, a second die might handle high-speed interfaces, and other chiplets might be intended for memory, power management, or specific safety and control functions.

This decomposition allows each element to be given a different level of robustness to radiation. Mission-critical control logic could be implemented on a chiplet made with radiation-tolerant (RT) technology, while some less critical peripheral functions could use components with different characteristics, as long as the overall architecture is verified against the intended operating environment.

The presence of RT FPGAs available today, such as Microchip Technology's RT PolarFire devices, highlights that the technology can achieve high levels of immunity.

A chiplet architecture could extend the principle and concentrate the most expensive resources where they produce the greatest benefit. However, the partition must also consider error propagation; in fact, a peripheral I/O chiplet can become critical if a single error alters protocols, buffers, clocks, or control signals that feed the main logic.

Radiation tolerance as a priority for the entire system

Physically separating functions does not eliminate the effects of radiation or automatically classify a system as radiation-tolerant. Tolerance must be evaluated at the level of device, package, interconnects, and logic architecture, considering different phenomena such as total ionizing dose, single-event upset, single-event transient, and single-event latch-up.

If the performance of an FPGA in a radiative environment depends on the possibility of a critical part of the device being damaged, in parallel, mitigation techniques can reduce the likelihood that a transient event will cause a functional loss. In a chiplet system, it is therefore necessary to specify well-defined fault domains.

A possible strategy is to avoid indiscriminately tripling the entire system, concentrating redundancy on functions whose failure can compromise the mission. The result can be a more efficient platform in terms of area and power, but only if the partition maintains controllable fault paths and if the interfaces between chiplets are designed as functional elements of the reliability chain rather than as simple electrical connections.

Performance

The main challenge of an FPGA chiplet solution is the transfer of data between the dies. A high-performance computing fabric can lose some of its benefits if each operation requires frequent die-to-die interconnect traversals, introducing latency, power consumption, and complexity in clock management. Modern chiplet architectures seek to reduce this penalty through high-bandwidth interconnections and standardized protocols.

For a space-bound FPGA, however, the choice of interface cannot be made by considering only bandwidth and latency. It is also necessary to evaluate the probability of error, the possibility of detecting corrupted packets, the management of resets, synchronization, and the ability to isolate a failed domain. An effective architecture could therefore keep resources that require very frequent communication locally in the computing chiplets, using the die-to-die link especially for structured flows, shared memory, and I/O. The topology thus becomes an integral part of an FPGA design.

Packaging and interposers become part of the reliability problem

With chiplets, the package takes on an importance comparable to that of silicon, as the interposer and die-to-die connections become essential elements of the platform. In a terrestrial application, a very high-density interconnect is evaluated for signal integrity, cost, and production efficiency, while in space, it is necessary to add thermal cycles, vibrations, vacuum, reliability of connections, and behavior under radiation.

In extreme-environment electronic applications, device technology, packaging, temperature, and radiation must be considered simultaneously because the traditional approach based on individually qualified components does not always describe the behavior of a complete system. A chiplet package should be qualified as an integrated platform, with a focus on microbumps, interposers, power distribution, and clock integrity.

Even a passive interposer cannot be considered automatically irrelevant from the point of view of reliability, because a defect or degradation in the connections can interrupt several functions at the same time. The advantage of modularity must be balanced with a new verification surface, in which the package is included in the definition of the architecture and qualification activities.

Upgradeability and lifecycle

One of the most attractive advantages of modularity emerges when considering the typical lifespan of space programs. A project can remain in development for many years, while production processes, interfaces, and computing technologies can evolve rapidly. A monolithic architecture tends to tie all these variables together, making it difficult to replace a single function without reopening a significant part of the qualification process.

A chiplet platform, on the other hand, can define relatively stable functional interfaces, allowing the computing or the communications chiplet to be upgraded, leaving part of the architecture unchanged. However, the concept requires strict dependency management: Changing a die can change timing, power consumption, thermal dissipation, package compatibility, and radiative behavior.

Upgradeability should therefore not be interpreted as a free replacement of components but as a design possibility from the outset. One possible solution is to maintain a qualified I/O and control chiplet for multiple generations, while the computational part evolves according to the needs of the mission. The same philosophy can apply to dedicated accelerators, memory, and communication functions. In this way, the project acquires a certain technological elasticity without sacrificing the traceability necessary for a system destined to operate for years without physical intervention.

Final considerations

The adoption of chiplets in FPGA computing for radiative environments should not be considered simply as a new silicon assembly. This method provides a different way to distribute reliability and performance while providing the ability to upgrade across the entire architecture.

The separation of compute, I/O, memory, and control functions can allow RT technology to be concentrated in the truly critical areas, eliminating the need to apply the same level of qualification to every function in the system. The advantage becomes particularly significant when the mission requires high performance and a very long lifecycle, conditions in which the availability of components, together with the evolution of production processes and qualification costs, can affect the nominal performance.

Finally, the design of an FPGA for radiative applications requires a more complex verification methodology than that of a monolithic device. It is not enough to characterize each chiplet separately because the behavior of the system can depend on the interactions between die, interposer, power supply, and firmware.

The methodology should start with a classification of functions based on their criticality, identifying which errors can be corrected locally, which must be reported to the system, and which require reconfiguration.

Today, RT FPGAs already exist that offer significant logic resources, memory, and connectivity, while research into reconfigurable FPGA architectures continues to explore techniques to increase reliability and upgradeability.

The move to chiplets, however, also introduces design responsibilities. Interposers, die-to-die links, power supply, and packages become integral parts of the reliability chain. For embedded systems intended for space, the true value of technology therefore lies in the possibility of designing an evolving platform, in which each function has a level of robustness consistent with its role while the entire system remains verifiable during all phases of the program.

The post Chiplet-Based FPGAs Optimize Performance for Space Applications appeared first on Embedded.