Modeling Static Delay Variations in Push-Pull CMOS Digital Logic Circuits Due to Electrical Disturbances in the Power Supply

Soft errors can occur in digital integrated circuits (ICs) as a result of an electromagnetic disturbance, such as might result from an electrical fast transient (EFT). Many soft errors come from changes in propagation delays through digital logic, which are caused by changes in the on-die power supply voltage. An analytical model was developed to predict timing variations in digital logic as a result of variations in the power supply voltage. The derivation of the analytical delay model is reported. The model was validated experimentally by applying EFTs to a ring oscillator built in a test IC. The predicted and measured ring oscillator frequencies (or periods) agreed within a relative error of less than 2.0%. To further validate the approach, the model was applied to test the response of more complex circuits consisting of NAND/NOR logic gates, binary adders, dynamic logic gates, and transmission gates. The circuits were fabricated on a 0.5 μm test IC and simulated on two additional process technologies (0.18 μm and 45 nm). The model performed well in each case with a maximum relative error of 5.6%, verifying the applicability of the model for analyzing complex logic circuits within a variety of process technologies. The proposed delay model can be used by IC design engineers to predict and understand the change in the propagation delay through logic circuits due to the disturbed power supply.