Temporal sequential logic hardening by design with a low power delay element

Abstract

A reduced power delay element for the temporal hardening of sequential digital circuits is presented. The delay element single event transient (SET) tolerance is demonstrated by simulations using it in a radiation hardened by design (RHBD) master slave flip-flop (FF). Using the proposed delay element saves up to 25% total FF power at 50% activity factor. The delay element incorporates redundancy to mask long transients, which would otherwise limit the circuit hardness. Two FF layouts using the proposed delay element are used in synthesis and auto-place and route experiments to confirm overall power, performance, and density. The first (interleaved) version uses a multi-bit cell interleaving the constituent circuits of four FFs. The second (inline) version interleaves the master and slave circuits to achieve high density while maintaining adequate critical node separation. The latter is shown to be more power efficient and the former is more robust to multiple node collection.