Mike Wens

A Fully Integrated CMOS 800-mW Four-Phase Semiconstant ON/OFF-Time Step-Down Converter

A fully integrated dc-dc four-phase step-down converter in a 130-nm 1.2-V CMOS technology is realized with integrated metal-track inductors and integrated MOS and MIM capacitors. The converter requires no external components and is designed to generate an output voltage of 1.2 V out of a 2.6 V supply voltage. The maximum power-conversion efficiency is 58%, for a voltage-conversion ratio of 0.46. This yields a 21% improvement over a linear converter. The maximum output power is 800 mW and the power density of 213 mW/mm2 is in the same order of magnitude of nonintegrated switching converters, even when not taking their off-chip output filter into account. Stacked transistors are used to cope with the high voltage. A novel control system based on semiconstant ON/OFF time (SCOOT) regulates the output voltage. It also provides stability over the entire load range from 0 to 800 mW. The four-phase topology and the SCOOT control system ensure an output voltage ripple below 10% of the output voltage. The converter operates in discontinuous, synchronous switching mode. The switching frequency varies with the load from 75 kHz to 225 MHz.

A fully-integrated 130nm CMOS DC-DC step-down converter, regulated by a constant on/off-time control system

A fully-integrated DC-DC step-down converter in a 130 nm 1.2 V CMOS technology is realized, with an integrated metal-track inductor and integrated MOS and MIM capacitors. The converter is designed to generate an output voltage of 1.2 V out of a 2.6 V power supply. No external components are required. The maximum power conversion efficiency is 52%, for a voltage conversion ratio of 0.46. This is a 12% improvement compared to a linear regulator. Higher values are likely to be reached using a converter with external components, which is not the case here. Stacked transistors are used to cope with the high voltage. A novel control system based on a constant on/off-time keeps the output voltage constant at load conditions from 0 mW to 180 mW. The converter operates in discontinuous, asynchronous switching mode. The switching frequency ranges from 30 Hz to 300 MHz.

Design and Implementation of Fully-Integrated Inductive DC-DC Converters in Standard CMOS

CMOS DC-DC Converters aims to provide a comprehensive dissertation on the matter of monolithic inductive Direct-Current to Direct-Current (DC-DC) converters. For this purpose seven chapters are defined which will allow the designer to gain specific knowledge on the design and implementation of monolithic inductive DC-DC converters, starting from the very basics.

A fully-integrated 0.18μm CMOS DC-DC step-down converter, using a bondwire spiral inductor

A fully-integrated DC-DC step-down converter in a 0.18 mum 1.8 V CMOS technology is realized, with a bondwire spiral inductor and integrated MOS and MIM capacitors. The converter is designed to generate an output voltage of 1.8 V out of a 3.6 V power supply. No external components are required. The maximum power conversion efficiency is 65 %, for a voltage conversion ratio of 0.5. This is a 23 % improvement compared to a linear regulator. Higher values are likely to be reached using a converter with external components, which is not the case here. Stacked transistors are used to cope with the high voltage. A novel control system based on a constant on/off-time keeps the output voltage constant at load conditions from 0 mW to 300 mW. The converter operates in discontinuous, asynchronous switching mode. The switching frequency ranges from 20 Hz to 140 MHz.

A DMOS integrated 320mW capacitive 12V to 70V DC/DC-converter for LIDAR applications

A 320mW integrated switched capacitor DC-DC converter is realized in a 0.35µm DMOS high voltage technology. This 10 stage converter generates 70V from a 12V voltage supply, at a maximum efficiency of 85.5% per stage. An on-chip control system varies the clock frequency from 0 to 35.4MHz in order to regulate the output voltage at varying loads and supply voltages. Each of the stages uses an integrated capacitor of 74pF. The total area of the chip is 6mm2.

DC-DC converters: From discrete towards fully integrated CMOS

Monolithic integration of electronic systems is one of the major techniques to reduce cost, size and power consumption in state-of-the-art consumer applications. Integration of transceivers and other mixed-signal building blocks has proven to be a very successful approach to build low cost, compact and portable systems [1]. Remarkably a certain building block remains discrete in commercial applications: the switched-power supply. This paper will demonstrate how recent research efforts cleared the path to develop fully integrated DC-DC converters in standard CMOS.

Basic DC-DC Converter Theory

Several methods exist to achieve DC-DC voltage conversion. Each of these methods has its specific benefits and disadvantages, depending on a number of operating conditions and specifications. Examples of such specifications are the voltage conversion ratio range, the maximal output power, power conversion efficiency, number of components, power density, galvanic separation of in- and output, etc. In order for the designer to obtain a clear view of the DC-DC voltage conversion methods and their individual advantages and disadvantages, with respect to monolithic integration, the three fundamental methods are discussed in this chapter. The first and oldest method of performing DC-DC voltage conversion is by means of linear voltage converters (resistive dividers), which are explained in Sect. 2.1. The second method is by means of capacitor charge-pumps, as explained in Sect. 2.2. The latter two methods are explained more briefly as this work will mainly concentrate on inductive type DC-DC converters, which are discussed in Sect. 2.3. Power conversion efficiency is in most cases a primary specification for any given energy converter. Therefore, a formal method for the fair comparison of DC-DC step-down voltage converters, in terms of power conversion efficiency, is introduced in Sect. 2.4. This method is referred to as the Efficiency Enhancement Factor (EEF). The chapter is concluded in Sect. 2.5.

A Mathematical Model: Boost and Buck Converter

Monolithic DC-DC converters in standard CMOS are characterized by very low values for the capacitors (nF) and inductors (nH). As a result, the switching frequency will be much higher compared to converters with external components, in the order of hundred MHz. This high switching frequency, in terms of DC-DC conversion that is, will introduce significant switching-losses due to several parasitic effects. Therefore, it is self evident that the basic equations for describing ideal DC-DC converters will not suffice for the design of their monolithic variants. Moreover, this design process will be executed in a multi-dimensional design space, making it considerably complex for the designer to find the optimal design. For these reasons it is understood that the deduction of an accurate mathematical model will yield a more efficient design flow, in addition to an improved understanding of the important trade-offs. The fundamental equations and the method to calculate the output parameters are deduced for both a boost and a buck converter in Sect. 4.1. The resistive losses, together with dynamic losses, are caused by the non-ideal properties of the converter components and they are modeled in Sect. 4.2. The effects of this increased temperature are modeled in Sect. 4.3. The final model will be used in Sect. 4.4 to deduce generally valid, qualitative trade-offs for monolithic DC-DC converters. The chapter is concluded in Sect. 4.5.

An integrated 10A, 2.2ns rise-time laser-diode driver for LIDAR applications

An integrated laser-diode driver for LIDAR applications in a 0.35 µm 80V CMOS technology is realized. The integration of the power switch as a n-DMOS allows a peak current of 10 A, with a corresponding rise-time of 2.2 ns and a fall-time of 2.4 ns. Up to the authors knowledge this is a first-time achievement on a monolithic die. The laser can be operated at a maximum duty-cycle of 0.1 %, with a pulse duration of 10 – 50 ns. To overcome the parasitic inductances and their associated voltage drop, a high voltage of 70 V is applied to the LIDAR circuit. In order to drive the power switch within its safe operating area and to make sure the rise- and fall-time is minimized, a pre-driver is integrated on the same die.

On-chip high performance magnetics for point-of-load high-frequency DC-DC converters

This paper presents the design, fabrication, and characterization of on silicon integrated micro-transformers for high frequency power applications. The microtransformer device is used and tested in DC-DC converter application at high switching frequency. This device has stable L vs. f characteristic up to 50 MHz. The design is improved regarding to the electrical resistance and current capability. The microtransformer shows an inductivity of about 60 nH, resistance of 350 mΩ and can be applied for current up to 1.5 A.