Modeling of a Voltage Regulator Module for Power Integrity: Power Supply Induced Jitter

This article analyzes different methods for modeling a buck regulator among the variety of voltage regulator modules from the perspective of power integrity and assesses the accuracy of power supply induced jitter (PSIJ) predictions for each buck regulator model. To compare the buck regulator modeling approaches, methods for conventional passive component modeling and behavior modeling are introduced. Four different buck regulator models are compared with measurements in terms of time-domain voltage ripple and nonlinearity. Then, each model is applied to a simulation-based system-level PSIJ prediction setup to quantify the accuracy of the buck regulator models from the perspective of PSIJ. A printed circuit board with an inverter chain powered by an external buck regulator is selected as the device under test. In the presence of power supply fluctuations due to load current injection on the buck regulator, the time interval error of the inverter is measured. The measured peak-to-peak jitter is then reproduced by various simulation setups with the different buck regulator modeling methods. Finally, the PSIJ simulation accuracy is investigated for each buck regulator model.