GHz-range characterization and modeling of power integrity in SiP for an array of switch-mode converters

Abstract

The trend of miniaturization has been spread to a vast variety of circuits. Among those, there is a need to integrate in a more compact way power electronic circuits and switch-mode converters. Accordingly, the concept of Configurable Power Input and Output System (CPIOS) is introduced. Such a system integrates into the same compact substrate switch-mode converters, sensitive analog circuits for control and readback together. That type of system brings new challenges in terms of power integrity. Indeed, the switching activity from the switch-mode converters generate noise onto the power rails of the CPIOS, thereby impeding the performances of the more sensitive circuits. There is a need to predict voltage fluctuations generated by the switching activity of one or multiple converters switching simultaneously onto those more sensitive circuits, in terms of shape, peak amplitude and power spectral density, in order to assess the degradation of the performances. Moreover, multiple converters may switch simultaneously in CPIOS, increasing the complexity of predicting that noise. Furthermore, the characterization of the current is equally important in order to assess power integrity due to it being the main noise generation mechanism. Therefore, there is also a need for embedded current measurement technique with minimal required on-board provisions and a bandwidth better than available from the state-of-the-art techniques. The main objective of this research is to model power integrity constraints in CPIOS based on the different operating conditions and a thorough characterization of the system. The first specific objective is to characterize the switching currents in power converters for the CPIOS, which are critical for predicting power integrity with high bandwidth. Accordingly, a transmission-linebased current measurement technique is proposed. A thorough analytical formulation of the behavior of the structure shows that its measurement distortion can be predicted at up to multiple GHz and that the probing pad can be placed at any convenient location on the substrate without affecting measurement distortion. Measurements with the transmission-line-based structure validated with the well-known resistive shunt technique show that the current in a switch-mode converter can be characterized at up to 1.95 GHz with less than 3 dB measurement distortion. Such results are an improvement over the state of the art in terms of frequency, compactness and ease of implementation of the embedded technique. The second specific objective is to predict fluctuations onto the power rails of sensitive circuits, in terms of shape and energy spectrum. For that purpose, a model for power integrity and voltage fluctuations during simultaneous switching of the converters on power rails is presented. For every condition validated, accuracy better than 10 dB is obtained between 0 and 2 GHz by comparing a measured reference signal and predictions when the fluctuations caused by a single or multiple converters are measured. In terms of overall shape, the variance-normalized mean squared error (NMSE) in the worst case is of 0.624 and under numerous conditions better than 0.25. This model is the first of its kind to predict power integrity in the context of power converters at up to multiple GHz.

Date	10 Apr 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Yves Blaquière (Supervisor) & Nicolas Constantin (Co-supervisor)