Cost-effective application of advanced commercial electronics technologies in DoD space systems requires early development of radiation-hardened-by-design (RHBD) techniques, and use of simulations is critical to the efficiency of this process. CFDRC has developed an integrated, mixed-mode simulation approach allowing their NanoTCAD device physics simulator to interface with commercial circuit simulator used in foundry process design kits (PDKs). This integrated approach: (1) maintains required fidelity of radiation-response mechanisms without the need for new compact model development for each technology, (2) overcomes limited compact model availability in TCAD tools for mixed-mode simulations, and (3) allows for larger circuit to be simulated vs. practical using TCAD alone, while leveraging foundry-supported compact models. This project will combine CFDRCs unique mixed-mode capability with Vanderbilts experience in RHBD approaches for digital and analog/mixed-signal circuits. Phase I will demonstrate efficacy of the approach through application to a case where TCAD fidelity is required to capture radiation-response mechanisms and the electrical response of surrounding circuitry is necessary to determine the circuit response. Phase II will automate the mixed-mode setup and calculation procedures, and apply the upgraded tools to additional technology and RHBD demonstrations. Phase III will deliver a high-value documented simulation flow for application to RHBD library development.