Analog Mixed-Signal Circuit Splitting and Defect Simulation Method Based on Signal Flow Diagram

Abstract

Comprehensive defect simulation in the integrated circuit design stage is the basic guarantee to improve testability, which is also the basic requirement of current automotive-grade chip design. For example, there are six types of basic defect models for a single MOS transistor in a circuit, and the defect set of analog/hybrid integrated circuits containing thousands of devices is extremely large. It is very time-consuming to inject a large number of defects one by one and solve them in a large-scale matrix. In fact, the complete defect simulation often takes months or even years, and there is no good solution at present. In this article, a circuit splitting method based on signal flow and graph analysis is proposed, which models the control relationship between the device current and voltage nodes of the circuit with a directed dependence graph (DDG) through signal flow analysis. Then, more weak connections are obtained by identifying and breaking the feedback loops of larger strongly connected components (SCCs), and the weak connectivity in SCCs is split to realize circuit splitting. The acceleration can then be achieved by parallel defect simulation. At the same time, in order to investigate the observability of the internal defects in the previous SCCs in the subsequent SCCs, the defects were simulated according to the one-way transfer relationship between each SCC in a directed acyclic graph (DAG). An equivalent compression method of the defects and the signal in the transfer process is proposed, which reduces the number of simulation times of the defects. Finally, this article takes the benchmark BANDGAP, LDO, and SARADC circuits as examples and uses HSPICE simulation to verify the effectiveness of the graph splitting method. Compared with the latest transistor-level circuit splitting scheme, the circuit splitting algorithm proposed in this article can split more and smaller circuit blocks. Using the circuit blocks, we have divided to implement the parallel defect simulation scheme, and the defect transfer simulation scheme is more effective than the traditional full-circuit and full-defect simulation one by one.