Electrical and Thermal Characterization of an Inductor-Based ANPC-Type Buck Converter in 14 nm CMOS Technology for Microprocessor Applications

Abstract

Integrated Voltage Regulators (IVRs) are attractive substitutes for conventional voltage regulators located on the motherboards, due to outstanding dynamic performances and superior power densities. IVRs operate with switching frequencies in the range of 100 MHz and are assembled in highly compact packages close to the microprocessor load. This paper presents a comprehensive characterization of a PCB-and inductorbased four-phase ANPC-type IVR that uses a Power Management IC (PMIC) implemented in a 14 nm CMOS technology node. The characterization is based on the results of electrical measurements, thermal inspections of the chip surface, and simulations, which enables the separation of the total losses into on-chip and off-chip loss components and the allocation of important loss components inside the chip. The investigated IVR achieves a maximum efficiency of 84.1 % at an output power of Pout = 640 mW and a switching frequency of fs = 50 MHz. The thermal measurements reveal that the maximum efficiency of the PMIC itself is between 88 % and 90 % at fs = 50 MHz and Pout ∈ [500 mW, 600 mW]; at Pout = 890 mW, a chip current density of 24.7 A/mm 2 is achieved. The findings in particular point out that the losses in the chip-internal interconnections, i.e., the conductors of the Power Distribution Network (PDN) and the twelve stacked metal layers below the PDN, have a substantial contribution to the total losses. Furthermore, the combination of Cadence post-layout simulations with impedance networks obtained from an appropriate software tool, e.g., FastHenry, is found to establish a suitable toolbox for estimating losses in IVRs.

Active Thermal Control in Neutral-Point-Clamped Multilevel Converters based on Switching-Cell Arrays

“…The Neutral-Point-Clamped (NPC) multilevel converter [1], [2] is currently a well-established topology for many applications [3]- [7], within a wide range of power and voltage ratings. The benefits and drawbacks of NPC multilevel converters have been widely reported in the literature [8], [9].…”

A Survey on Capacitor Voltage Control in Neutral-Point-Clamped Multilevel Converters

“…Since then, technical evolution has provided enhanced power semiconductor technologies, faster digital processors to implement modulation and control, and thousands of technical papers providing a deeper knowledge about the multilevel converter operation. This development has made multilevel converters suitable not only for high voltage and high power but also for low-medium voltage and power applications [24][25][26][27][28][29]. For high-voltage and high-power applications, the lower device voltage rating is the most valuable feature of multilevel converters.…”

“…Some applications of NPC multilevel converters are motor drives [23,42,43], photovoltaic power generation [32,[44][45][46], wind power generation [47][48][49], static synchronous compensation [10,50], and DC-DC conversion [29,51].…”

Experimental Efficiency Evaluation of Stacked Transistor Half-Bridge Topologies in 14 nm CMOS Technology

“…In addition, it is desirable to reduce the high package currents of modern microprocessors. Reduced package current and adjustable supply voltages for the different VDs can be achieved with buck-type Integrated Voltage Regulators (IVRs) that are located in the package of the microprocessor or on the microprocessor die [6]. Table 1 summarizes the main specifications of the considered IVR.…”

“…Accordingly, inductor-type buck converters are often preferred if the ratio of input-to-output voltage is variable. Documented realizations include multi-phase buck converters with on-die inductors with a magnetic core [12], on-package air core inductors [13], and discrete inductors [6]. In addition, numerous improvements have been presented in the literature, e.g., the use of discontinuous conduction mode [14] and the implementation of a small SCC that is connected in parallel to the output of the buck converter [15], to achieve increased efficiencies under medium-and light-load conditions, respectively.…”