The Research On The Total Dose Effect And Its Infacts Of SRAM-based FPGA

With the continuous development of space technology and the rapid growth of the transmission data of information, people’s demand for data transmission rates also have increased, raising from magnitude of Mbps to Gbps(even as large as tens Gbps). In terms of traditional microwave communication, owing to the limitation of the carrier frequency, the data rate is difficult to reach the magnitude of Gbps. However, satellite communication technology, which takes laser as an carrier of information, is an excellent solution. Compared to conventional microwave communication technology, satellite laser communication technology has ma ny advantages: high data rate(up to tens of Gb/s or more), strong anti-interference ability, good privacy, less mass, less volume and low power consumption, etc.In a system of satellite optical communication, SRAM-based FPGA is playing an important role in high speed data collection and system control because of its strong programming ability, high integration, low power consumption, high speed and other characteristics. Nowadays, however, there is a great gap in manufacturing technology of FPGA chips between China and United States. Meanwhile, it is difficult to obtain FPGA of military and aerospace grades, owing to not only the restrictions of the embargo policy of the United States, but also a high price. In contrast, commercial SRAM-based FPGA devices have great potential applications in satellite optical communication terminal system for the cheap and accessible characteristics.However, space satellites and other spacecraft run in a very complex radiation environment. When the laser communication terminals work at the orbits, SRAM-based FPGA chip in systems will be affected by radiation, which will result in the degradation of the electrical properties of the entire chip. The main symptoms are the increase of working current or even functional failures, threatening security and reliability of the laser communication terminal in orbits. Therefore, it is necessary to study the space radiation effects of SRAM-based FPGA and assess the reliability of its space applications.In this paper, the total dose effect of SRAM-based FPGA in the space radiation environment was studied theoretically and experimentally. Firstly, application and research status of SRAM-based FPGA in aerospace are summarized; secondly, in terms of space radiation theory, the mechanism of total dose effects of SRAM-based FPGA were analyzed; thirdly, In this paper, the commercial SRAM-based FPGA of Virtex-5 series was used in the experiment to simulate the total dose radiation effects on the ground by use of 60Co-? radiation source. The results show that once cumulative radiation dose on FPGA chip reaches a certain value, the current consumption increases with cumulative doses rise. But, the device does not display functional failures within the test radiation dose. Finally, we reach the conclusion that the failure threshold of the total dose of SRAM-based FPGA chip exceeded 70 krad(Si), which meet three-year total dose requirements of on-orbit work of LEO satellite. Furthermore, the annealing effects of SRAM-based FPGA chip after irradiation were studied in this paper. The results show that the current of FPGA changes dramatically in the initial stage of annealing; about three days after annealing, the current tends to be steady. 250 hours after annealing, however, the current cannot return to the previous level before irradiation, in addition, during the period of annealing, the experiment device does not show function fails.