Mixed-signal Design Methodology Using a Priori Single Event Transient Rate Estimates

Mixed-signal integrated circuits used in space applications are exposed to solar particles and galactic cosmic rays (GCR). For earth orbit environments, the energy and composition of the particle radiation depends primarily upon the orbital inclination and the orbit altitude. However, due to the solar cycle and its interaction with the GCR, there is also a time dependence to the intensity and energy composition of the particle radiation [1]. Both forms of particle radiation can cause deleterious effects in microelectronics, including single event latch-up (SEL), single event upsets (SEUs), single event transients (SETs), or single event effects (SEE), some of which are irreversible and destructive to the electronics. SET and SEU rates are typically determined from particle accelerator experiments on test structures containing analog and digital cells that will be incorporated into a new Application Specific Integrated Circuit (ASIC) design. The cost and schedule impact of doing this for each cell in a full-custom, mixed-signal ASIC makes this approach impractical. Furthermore, the solid angle available for particle accelerator experiments is limited by both the available beam energies and the thickness of the layers of metal and dielectric material over-lying the sensitive device regions [2]. Whereas the particle energies in space environments make it possible to have heavy ion strikes that deposit charge in multiple sensitive regions, beam line experiments are often limited to probing only a single sensitive region at a time. While radiation testing of the prototype mixed-signal ASIC is certainly required, a cost-effective means of making a priori estimates of SET/SEU rates is required to avoid costly re-designs of full-custom mixed-signal ASICs. To calculate such error rates, including the effects of angled ion strikes, fully three-dimensional (3-D) simulations are needed.