This article presents the design and optimization of a miniaturized 48-V-to-1-V, 240-A linear-extendable group operated point-of-load (LEGO-PoL) CPU voltage regulator module (VRM)—Mini-LEGO—with a volume of 30 mm × 11.2 mm × 8.4 mm. The Mini-LEGO converter provides vertical power delivery and achieves a peak efficiency of 87.1%, a full load efficiency of 84.1%, and a power density of 1390 W/in³ when stepping down a 48 V input voltage to an output voltage of 1 V. The Mini-LEGO offers compact device implementation, simple gate drive circuitry, and a fast regulation-stage switching frequency of 1.5 MHz. The 9-mm-by-9-mm, 4-phase, 20-A-per-phase vertical coupled inductor has a per-phase transient inductance of 10.3 nH, with its coupling reducing the ripple by a factor of six, and a height of 2.5 mm. This vertical coupled inductor structure is designed following a systematic approach to minimizing its height while achieving significant current ripple reduction and maintaining sufficient saturation margin. Thermal simulations are performed to verify the cooling feasibility. A measurement characterization method for vertical coupled inductor structures is introduced and used to characterize the designed vertical coupled inductor. The Mini-LEGO reduces the height of the 48-V VRM from 16.65 to 8.4 mm as compared to the LEGO-PoL design. It has a current area density of 0.71 A/mm² and achieves a power density of 1390 W/in³, including all gate drive circuitry, achieves 87.1% peak efficiency, does not require liquid cooling, and is thin enough for highly compact system packaging. The multiphase buck regulation stage switches at 1.5 MHz. Mini-LEGO tradesoff energy efficiency to realize improvements in power density and control bandwidth. The miniaturized size and thickness allows the VRM to be packaged much closer to the microprocessor where abundant cooling resources are available, mitigating the challenges of thermal management due to lower efficiency. The article presents the optimal design of a new hardware implementation of the LEGO-PoL architecture—the Mini-LEGO converter—to demonstrate its capability at a higher switching frequency for extreme performance. The operation principles of the architecture are reviewed in Section II, and the design methodology of the Mini-LEGO converter is presented in Section III. The operation of the simplified gate driver circuit is explained in Section IV. A novel coupled magnetics geometry is introduced, suitable for vertical power delivery, with parameters that enable the tradeoff between core losses and winding losses while reducing inductor height. A loss-based optimization method is presented and the design of a four-phaseThis article presents the design and optimization of a miniaturized 48-V-to-1-V, 240-A linear-extendable group operated point-of-load (LEGO-PoL) CPU voltage regulator module (VRM)—Mini-LEGO—with a volume of 30 mm × 11.2 mm × 8.4 mm. The Mini-LEGO converter provides vertical power delivery and achieves a peak efficiency of 87.1%, a full load efficiency of 84.1%, and a power density of 1390 W/in³ when stepping down a 48 V input voltage to an output voltage of 1 V. The Mini-LEGO offers compact device implementation, simple gate drive circuitry, and a fast regulation-stage switching frequency of 1.5 MHz. The 9-mm-by-9-mm, 4-phase, 20-A-per-phase vertical coupled inductor has a per-phase transient inductance of 10.3 nH, with its coupling reducing the ripple by a factor of six, and a height of 2.5 mm. This vertical coupled inductor structure is designed following a systematic approach to minimizing its height while achieving significant current ripple reduction and maintaining sufficient saturation margin. Thermal simulations are performed to verify the cooling feasibility. A measurement characterization method for vertical coupled inductor structures is introduced and used to characterize the designed vertical coupled inductor. The Mini-LEGO reduces the height of the 48-V VRM from 16.65 to 8.4 mm as compared to the LEGO-PoL design. It has a current area density of 0.71 A/mm² and achieves a power density of 1390 W/in³, including all gate drive circuitry, achieves 87.1% peak efficiency, does not require liquid cooling, and is thin enough for highly compact system packaging. The multiphase buck regulation stage switches at 1.5 MHz. Mini-LEGO tradesoff energy efficiency to realize improvements in power density and control bandwidth. The miniaturized size and thickness allows the VRM to be packaged much closer to the microprocessor where abundant cooling resources are available, mitigating the challenges of thermal management due to lower efficiency. The article presents the optimal design of a new hardware implementation of the LEGO-PoL architecture—the Mini-LEGO converter—to demonstrate its capability at a higher switching frequency for extreme performance. The operation principles of the architecture are reviewed in Section II, and the design methodology of the Mini-LEGO converter is presented in Section III. The operation of the simplified gate driver circuit is explained in Section IV. A novel coupled magnetics geometry is introduced, suitable for vertical power delivery, with parameters that enable the tradeoff between core losses and winding losses while reducing inductor height. A loss-based optimization method is presented and the design of a four-phase