微处理器中子单粒子效应测试系统设计与试验研究

Design and Test of Neutron-induced Single Event Effect Monitoring System on Microprocessor

为开展微处理器的空间大气中子单粒子效应研究,以一款TI公司65 nm CMOS工艺的微处理器为研究对象,研制了一套微处理器中子单粒子效应测试系统。该测试系统可实现对被测微处理器的单粒子翻转、单粒子功能中断和单粒子闩锁效应的实时监测。利用加速器中子源,对该微处理器开展14 MeV中子辐照试验。试验结果表明,中子注量累积达3.5×10^(11)cm^(2)时,该器件未发生单粒子锁定效应。但总线通信、模数转换等功能模块发生了多次单粒子功能中断,其中集成总线通信接口模块为最敏感单位,试验获得的器件中子单粒子效应截面为6.6×10^(11)cm^(2)。

Cosmic rays interact with atmospheric atoms to generate high-energy neutron radiation, which threats to the electronic system working in the atmospheric space environment. Neutron-induced single event effect(SEE) occurring in the key component of an electronic system(i.e. microprocessor) seriously affects the system reliability. To study neutron-induced SEE of microprocessor, a SEE monitoring system was designed for a 65 nm CMOS microprocessor from Texas Instruments(TI). The designed system has the ability to monitor SEE events that occur in tested microprocessor, and record corresponding voltage/current change in real time. To minimize the irradiation-caused disturbance in monitoring system, it consists of two modules connected with 1.2 m communication line in irradiation room. One module carrying tested microprocessor is placed close to the neutron source. Another module acting as the master control board is placed as far away from the neutron source and is shielded against gamma ray with lead bricks. The upper order computer and 24 V direct-current(DC) power supply are placed outside of the irradiation room. As a key component of the SEE monitoring system, the master control board is composed of microcontroller unit(MCU), power management chip, operating voltage/current monitor and peripheral circuit. The master control board is able to continuously monitor the internal operating status of the tested microprocessor and the voltage/current fluctuation. The 24 V input voltage is converted into two-way power supplies. One is used for monitoring MCUs on master control board. Another one is used for the device under test(DUT). Operating voltage/current values are transferred to the upper order computer through a serial port. When the detected voltage or current values exceed set thresholds, monitoring MCU would cut off power supply through a relay. The SEE monitoring system was test using 14 MeV neutrons produced by D-T reactions. Single event functional interrupt(SEFI) was observed in inter-integrated circuit(I^(2)C), internal flash memory, analog-to-digital converter(ADC), arithmetic and logic unit(ALU), controller area network(CAN), general-purpose input/output(GPIO) and other units, while single event latch up(SEL) is not detected. I^(2)C is found to be the most sensitive unit. Neutron-induced SEE in I^(2)C bus leads to a significant operating current drop. Moreover, when one of eight tested I^(2)C buses is blocked under neutron irradiation, the following tests for rest I^(2)C bus will turn out to be “FAIL” too, which implies the SEE might occur at the control part of I^(2)C. The SEE cross-section of tested microprocessor is evaluated to be 6.6×10^(11)cm^(2) with the data of neutron fluence up to 3.5×10^(11)cm^(2).