Accurate Logic-Level Current Estimation for Digital CMOS Circuits

Nowadays, verification of digital integrated circuit has been shifting more and more from the timing and area field to current and power estimations. The main problem with this kind of verification is on the lack of precision of current estimations when working at higher levels (logic, RT, architectural levels). To solve this problem it is not only necessary to use good current models for switching activity, it is also necessary to calculate this switching activity with high accuracy. In this paper we present an alternative to estimate current consumption using logic-level simulation. To do that, we use a simple but accurate enough current model to calculate the current consumption for each signal transition, and a delay model that obtains high accuracy when it is used to measure the switching activity (the Degradation Delay Model (DDM)). In the paper we present the current model for the CMOS inverter, the characterization process and the model implementation in the logic simulator HALOTIS that includes the DDM. Results show a high accuracy in the estimation of current curves when compared to HSPICE, and a potentially large improvement over conventional approaches.