Michele Lim

A Class of Ceramic-Based Chip Inductors for Hybrid Integration in Power Supplies

A review of some of the available technologies for inductor hybrid integration is given in this paper. In accordance with low voltage and high current requirements, low-temperature co-fired ceramics (LTCC) technology is identified to be a suitable candidate for power electronics passives integration. This paper will discuss the various limitations of the current LTCC processing technique and introduce a fabrication technique which will open a new field for chip inductors for hybrid power electronics integration. The design of an LTCC inductor will also be presented. This inductor exhibits an inherent current dependent inductance, leading to high efficiency at low loads as an important systems advantage in portable electronics.

System design of a 3D integrated non-isolated Point Of Load converter

Thermal issues in the design of high-power and small-size non-isolated Point of Load (POL) converters have been significant and are becoming more so. If a heat sink is dispensed with, then a large area of multi-layer PCB material with significant amounts of copper is required for necessary cooling. A high-rate cooling fan is also necessary. So what at first seems like a small and elegant converter becomes bulky and challenging to position in the overall system when its thermal management is taken into account. This work finds a solution to these problems and investigates the use of Low- Temperature Co-fired Ceramic (LTCC) for integrating the inductor with the active stage. A buck POL is used to demonstrate these methodologies. The end result is a POL converter that can achieve full 20 A output current with no need for an external heat sink and no need for a cooling fan while providing a large step-down of 5 V to 1.2 V. High light- load efficiency of 92.2% is achieved and a high power density of 156 W/in3 including all the necessary thermal management, in natural convection condition, has been demonstrated.

Technology road map for high frequency integrated DC-DC converter

This preliminary road map is provided for state-of-the-art technologies and trends toward integration of point-of-load converters. This paper encompasses an extended survey of literature ranging from device technologies and magnetic materials to integration technologies and approaches. The paper is organized into three main sections. 1) Device technologies, including the trench MOSFET, lateral MOSFET and lateral trench MOSFET, are discussed along with their intended applications. The critical role of device packaging to high-frequency integration is assessed. 2) Magnetic materials: In recent years, a number of new magnetic materials have been explored in various research labs to facilitate magnetic integration for high-frequency POL applications. These data are collected and organized to help selecting magnetic material for various current levels and frequency ranges. 3) Levels of integration, which are defined with the focus on magnetic integration techniques and approaches, namely board-level, package-level and wafer-level, each with suitable current scale and frequency range.

Low Profile Integratable Inductor Fabricated Based on LTCC Technology for Microprocessor Power Delivery Applications

A novel low profile power inductor suitable for planar integration is designed and fabricated based on low temperature co-fired ceramics technology for microprocessor power delivery applications. The inductor was designed to operate at a switching frequency of 4 to 5MHz, carrying a nominal dc current of 20A with a ripple current of 8 to 10A in a 5-V to 1-V dc-dc converter. The design and fabrication procedure is discussed in this paper, followed by small signal measurement and magnetic characterization results. The inductor was implemented in a prototype converter and the large signal measurement results are presented and its performance evaluated

Technology roadmap for high frequency integrated DC-DC converter

This preliminary roadmap is provided for state-of-the-art technologies and trends toward integration of point-of-load converters. This paper encompasses an extended survey of literature ranging from device technologies and magnetic materials to integration technologies and approaches. The paper is organized into three main sections. 1) Device technologies, including the trench NIOSFET, lateral MOSFET and lateral trench MOSFET, are discussed along with their intended applications. The critical role of device packaging to highfrequency integration is assessed. 2) Magnetic materials: In recent years, a number of new magnetic materials have been explored in various research labs to facilitate magnetic integration for high-frequency POL applications. These data are collected and organized to help selecting magnetic material for various current levels and frequency ranges. 3) Levels of integration, which are defined with the focus on magnetic integration techniques and approaches, namely board-level, package-level and wafer-level, each with suitable current scale and frequency range.

Low profile integratable inductor fabricated based on LTCC technology for microprocessor power delivery applications

A novel low profile power inductor suitable for planar integration is designed and fabricated based on low temperature co-fired ceramics (LTCC) technology for microprocessor power delivery applications. The inductor was designed to operate at a switching frequency of 4 to 5 MHz, carrying a nominal DC current of 20 A with a ripple current of 8 to 10 A in a 5 V to 1 V DC-DC converter. The design and fabrication procedure is discussed in this paper, followed by small signal measurement and magnetic characterization results. The inductor is being implemented in a prototype converter and the measurement results are presented and its performance evaluated

Shielded LTCC Inductor as Substrate for Power Converter

The presence of a magnetic substrate below the circuitry created additional parasitic inductances, which resulted in low-frequency oscillations. From simulation, the presence of a metal shield reduces trace inductances and improves circuit performance. There is a minimum shield thickness required to minimize losses associated with ringing. High shield conductivity is necessary to lower the trace inductance and minimize power loss. Traces should be placed close to the shield to minimize inductance.

Applying the Steinmetz Model to Small Cores in LTCC Ferrite for Integration Applications

An empirical model for the low permeability LTCC magnetic material is developed based on Steinmetz equation, taking into account temperature variations and DC premagnetization. Steinmetz exponents and coefficient are expressed as a function of temperature and DC pre-magnetization to describe core loss for frequencies between 1 to 4 MHz, peak flux density between 5 mT to 50 mT, DC magnetic flux intensity, H, between 0 A/m to 1780 A/m and temperature range between 26 °C to 70 °C.

Research on LTCC Capacitors and its Potential for High Power Converters

In this paper, the fabrication of LTCC capacitor based on a high dielectric-constant LTCC capacitor paste is introduced. A simple analysis is made for failure modes in fabrication process. Small signal and high voltage performance is tested with a single-layer ceramic capacitor sample to prove the possibility to use it in high power converters

Errors in Electrical Core Loss Measurement for Extremely Small Samples Applicable to Integrated Converters

Accurate measurement of core loss of low loss magnetic materials in the milliwatts range for high frequency applications is difficult to achieve due to its sensitivity to measurement error especially when measured at high frequencies. Magnitude and phase errors from the oscilloscope, probes/cables, current viewing resistors, phase shift between voltage and current, and noise coupling into measurement probes, which affect the measurement accuracies will be analyzed in detail.