Research On Circuit Reliability Based On Approximate Calculation

With the shrinking of the scale of CMOS technology,integrated circuit design faces the challenge of increasing variability and reliability issues in the later stage of the CMOS era.Even in fault-tolerant applications,the effects of timing violation caused by transistor aging are intolerable.In the past,to avoid the effects of aging,a wide frequency guard band was usually added.The disadvantages of this method are that it leads to reduced efficiency and wastes additional area and power.The approximate calculation can improve the performance of the circuit while saving area and power when the accuracy loss is limited.This paper applies the emerging technology of approximate computing to circuit design,and proposes a new flow for enhancing circuit reliability.This flow uses a simplified compact transistor long-term aging model to quickly calculate the aging of the circuit,which can accurately evaluate the circuit.When the circuit can not meet the time constraints,the circuit is logically approximated until the time constraints are met.Eventually,the circuit can meet the time constraints and completely eliminate the guardband.This article uses image processing applications as an example.Since the cirtical path in the image processing circuit are adders,this article uses several redesigned approximate adders to replace the full adder in the original image processing application,and evaluates their reliability.Based on the above simulation results,this article also combines the advantages and disadvantages of some approximate adders proposed in recent years to propose a new approximate design method,and also evaluates its reliability.The evaluation results show that the method of approximate calculation can ensure the life of the circuit with limited image quality output loss.This method can convert critical path timing errors that are difficult to predict and seriously affect circuit reliability into deterministic logic simplification errors,so as not to affect the actual function of the circuit.Compared with traditional methods,using the concept of approximate computing to improve reliability in applications such as image / video processing is a more effective solution.