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There has been growing interest in single-inductor multiple-output (SIMO) dc-dc converters due to its reduced cost and smaller form factor in comparison with using multiple single-output converters. An application for such a SIMO-based switching converter is to drive multiple LED strings in a multichannel LED display. This paper proposes a quasi-hysteretic finite-state-machine-based digitally controlled single-inductor dual-output buck switching LED driver operating in discontinuous conduction mode (DCM) and extends it to drive multiple outputs. Based on the time-multiplexing control scheme in DCM, a theoretical upper limit of the total number of outputs in a SIMO buck switching LED driver for various backlight LED current values can be derived analytically. The advantages of the proposed SIMO LED driver include reducing the controller design complexity by eliminating loop compensation, driving more LED strings without limited by the maximum LED current rating, performing digital dimming with no additional switches required, and optimization of local bus voltage to compensate for variability of LED forward voltage VF in each individual LED string with smaller power loss. Loosely binned LEDs with larger VF variation can, therefore, be used for reduced LED costs. [ABSTRACT FROM AUTHOR]

Kinetic inductance is an important property of carbon nanotubes (CNTs) in high-frequency applications. However, disagreements exist in whether the kinetic inductance of CNTs is present in the diffusive transport regime. In this paper, we fabricated the horizontally aligned multiwalled nanotube (MWNT) arrays on silicon substrates and investigated the inductance properties of the MWNT arrays with different lengths using direct current and radio frequency characterizations. The experimental results show that the electron transport in the CNT arrays is diffusive and that the value of the kinetic inductance is proportional to the length of the CNT arrays. We have experimentally validated that the kinetic inductance theory is applicable to CNTs in the diffusive transport regime. This paper could quell the existing disagreements about the kinetic inductance and provide insights to the potential applications of CNTs as interconnects and on-chip inductors. [ABSTRACT FROM AUTHOR]

A physical-based analytical model for on-chip inductors is developed. A ladder structure is used to model the skin and proximity effects in metal lines. The substrate electric and substrate magnetic losses are accurately modeled by RC and RL ladder structures, respectively. The effective inductance reduction due to the eddy current in the lossy silicon substrate at high frequency is modeled by a negative mutual inductance between the inductor and the substrate. All the model parameters can be calculated from the layout and process parameters. On-chip inductors with different geometries and substrate resistivities were fabricated for the verifications. The measured results are in very good agreement with the proposed model. This generic model can be applied to various substrate resistivities; thus, it is suitable for different technologies. This model can facilitate the design and optimization of on-chip inductors for RF IC applications. [ABSTRACT FROM AUTHOR]