Schemes for eliminating transient-width clock overhead from SET-tolerant memory-based systems

Abstract

In the presence of radiation, particle strikes can cause temporary signal errors in ICs. Particle strikes that directly affect memory are known as single event upsets (SEUs), while strikes that affect combinational logic and spread to memory are called single event transients (SETs). In this paper, we propose two novel approaches to hardening integrated circuits against SEUs and SETs. The proposed approaches are fully-differential dual-interlocked storage cell (DICE) and triple path DICE (TPDICE). The fully-differential DICE and TPDICE approaches are compared against two existing approaches, which are triple modular redundancy (TMR) and basic SET-tolerant DICE. All approaches except for the basic SET-tolerant DICE scheme share a common theme, which is the ability to bypass SEUs and SETs. This is critical for performance, as it allows the system to proceed with subsequent operations while a cell is recovering from the effects of a particle strike. SET pulse widths can be substantial (up to 2 ns), and so high-performance systems cannot afford to pause operations while these pulses are present. The minimum clock periods obtained for the basic SET-tolerant approach were 515 ps with no SET, and 1310 ps with a 500 ps SET (in 0.18 /spl mu/m CMOS). In contrast, the clock periods for the bypass-capable approaches with no SET/500 ps SET were 628/749 ps for TMR, 348/480 ps for fully-differential DICE, and 434/552 ps for TPDICE. Among the approaches that bypass transient pulses, TPDICE is the most balanced. TMR suffers from overhead due to its need for external voting circuitry. In addition to this, fully-differential DICE cannot be used with combinational logic, while TPDICE can.