Optimized Power Supply Rejection Ratio Modeling Technique for Simulation of Automotive Low-Dropout Linear Voltage Regulators

Abstract

In the automotive domain, the vast majority of testing is performed through simulations, which can validate a system design before the actual implementation and can emphasize eventual faults in the design process. Hence, the simulation is of utmost importance. Behavioral models are necessary for the creation of each electronic device desired in the system, and some of the components have very complex behavior: low-dropout linear voltage regulators (LDOs), gate drivers, and switching regulators. In the automotive industry, LDOs are essential components because they power all the other subsystems and very accurate behavior is needed to make sure that the system behaves as in reality. LDO models are already commercially available and most of their intrinsic characteristics are modeled (dropout voltage, line regulation, load regulation, etc.). However, one characteristic that is extremely useful, yet the hardest to model, is the power supply rejection ratio (PSRR). This paper proposes a new PSRR modeling technique for automotive low-dropout voltage regulators. The new PSRR characteristic was modeled for an automotive LDO product in a Texas Instruments portfolio, which has a commercially available model, and was simulated using the PSpice Allegro simulator and the OrCAD Capture CIS environment.