Reliability of space-grade vs. COTS SRAM-based FPGA in N-modular redundancy

Abstract

In this paper, we evaluate the suitability of different SRAM-based FPGAs for harsh radiation environments (e.g., space). In particular, we compare the space-grade and radiation-hardened by design Virtex-5QV (XQR5VFX130) with the commercial off-the-shelf Kintex-7 (KC7K325T) from Xilinx. The advantages of the latter device are: 2.5 times the resources of the space-grade FPGA, faster switching times, less power consumption, and the support of modern design tools. We focus on resource consumption as well as reliability in dependence of single event upset rates for a geostationary earth orbit satellite application, the Heinrich Hertz satellite mission. For this mission, we compare different modular redundancy schemes with different voter structures for the qualification of a digital communication receiver. A major drawback of the Kintex-7 are current-step single event latchups, which are a risk for space missions. If the use of an external voter is not possible, we suggest triple modular redundancy with one single voter at the end, whereby the Virtex-5QV in this configuration is about as reliable as the Kintex-7 in an N-modular redundancy configuration with an external high-reliable voter.