Mohamed Bellaredj

Fabrication, Characterization and Comparison of FR4-Compatible Composite Magnetic Materials for High Efficiency Integrated Voltage Regulators with Embedded Magnetic Core Micro-Inductors

Integrated voltage regulators (IVRs) are considered nowadays as major elements in the development of power delivery networks for digital electronics because of their ability to implement point-of-load voltage regulation in multicore microprocessors and system-on-chip (SoC) architectures. Inductive regulators generally enable higher power efficiency over a wide range of conversion voltages. However, high efficiency IVRs require the integration of power inductors with low loss and reduced size at very high frequency. The use of a magnetic material core can reduce significantly the inductor area while increasing the inductance value at the same time. This paper focuses on the fabrication, characterization and modeling of Nickel Zinc (NiZn) Ferrite and Carbonyl Iron powder (CIP) epoxy composite magnet material which will be used as the magnetic core material of an embedded inductor in the PWB for SIP based buck type IVR. The fabricated composite materials and process are fully compatible with FR4 epoxy resin prepreg and laminate (PWB-compatible). The composite materials show (for 85% weigh loading, around 100 MHz at room temperature) a relative permeability between 7.5-8.1 for NiZn-composite (0.78 volume fraction) and between 5.2-5.6 for CIP composite (0.47 volume fraction) and a loss tangent value between 0.24-0.28 for NiZn-composite and 0.09- 0.1 for CIP-composite. The variation of the relative permeability and the frequency dispersion parameters of the magnetic composites are evaluated using Maxwell-Garnet Approximation (MGA) mixing rule and a simplified Lorentz and Landau-Lifshitz-Gilbert equation for Debye type relaxation. Evaluation of a buck type IVR based on the measured material properties shows that an embedded solenoidal inductor with an open core made with the NiZn Ferrite and CIP composite magnets can reach peak efficiencies of 91.7 % at 11 MHz for NiZn-composite, 91.6 % at 14 MHz for CIP-composite and 87.5 % (NiZn-composite) and 87.3 % (CIP-composite) efficiencies at 100 MHz for a 1.7V:1.05V conversion.

Modeling and design of system-in-package integrated voltage regulator with thermal effects

This paper demonstrates a new approach to model the impact of thermal effects on the efficiency of integrated voltage regulators (IVRs) by combining analytical efficiency evaluations with coupled electrical and thermal simulations. An application of the approach shows that a system-in-package solution avoids thermal problems typically observed in other IVR designs. While the evaluation in this paper focuses on the thermal impact on loss in the inductor wiring and the PDN, the developed approach is general enough to also model thermal impacts on the power dissipation in the inductor cores and the buck converter chip.

A Global Bayesian Optimization Algorithm and Its Application to Integrated System Design

Increasing levels of system integration pose difficulties in meeting design specifications for high-performance systems. Oftentimes increased complexity, nonlinearity, and multiple tradeoffs need to be handled simultaneously during the design cycle. Since components in such systems are highly correlated with each other, codesign and co-optimization of the complete system are required. Machine learning (ML) provides opportunities for analyzing such systems with multiple control parameters, where techniques based on Bayesian optimization (BO) can be used to meet or exceed design specifications. In this paper, we propose a new BO-based global optimization algorithm titled Two-Stage BO (TSBO). TSBO can be applied to black box optimization problems where the computational time can be reduced through a reduction in the number of simulations required. Empirical analysis on a set of popular challenge functions with several local extrema and dimensions shows TSBO to have a faster convergence rate as compared with other optimization methods. In this paper, TSBO has been applied for clock skew minimization in 3-D integrated circuits and multiobjective co-optimization for maximizing efficiency in integrated voltage regulators. The results show that TSBO is between

Miniaturization of Planar Packaged Inductor Using NiZn and Low Cost Screen Printing Technique

2times

A 65nm, 1.15–0.15V, 99.99% Current-efficient Digital Low Dropout Regulator with Asynchronous Non-linear Control for Droop Mitigation

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Multi-physics Modeling Characterization of Aerosol Jet Printed Transmission Lines

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A System-in-Package Based Energy Harvesting for IoT Devices with Integrated Voltage Regulators and Embedded Inductors

faster as compared with previously published BO algorithms and other non-ML-based techniques.

Fabrication of package embedded spiral inductors with two magnetic layers for flexible SIP point of load converters in Internet of Everything devices

Given the recent interest in power delivery design for the Internet of Things (IoT), current work aims to design a packaged power delivery solution for IoT. The power inductor takes up a large amount of the area in such an implementation. Planar power inductors are preferred for fabrication simplicity and cost. However, air core inductors do not have sufficient area efficiency for IoT solutions, necessitating the integration of a magnetic core on a planar inductor. This research demonstrates a low cost method of miniaturizing planar inductors using stencil printing technique with a magnetic composite for embedded power inductors for IoT edge device applications. Planar spiral inductors of varying dimensions and inductances are designed using a full wave EM solver. Inductors are then fabricated on FR4 using standard printed wiring board process. NiZn is a low loss magnetic material and is mixed with an epoxy and solvent to facilitate stencil printing. Stencil printing is a low cost fabrication method with great utility to electronic packaging. A single layer of NiZn is screen printed as squares directly on the fabricated spiral inductors. Measurements are performed using a vector network analyzer at frequencies between 10 and 50 MHz. The measured inductance of the inductors ranges from 37 nH-340 nH without NiZn to 42 nH-452 nH with a single NiZn layer at the operating frequencies. In addition, the Q factor is actually improved at the frequency of operation, as the inductance gained from the magnetic layer is more significant than the loss incurred. This increase in inductance leads to great potential for decrease of size of packaged inductors.