AI explosive growth and its consequent hardware evolution have brought a dramatic increase in power levels of the IT rack in datacenters, up to several hundred kW already today. This factor is obliging to evolve the conventional architecture of power distribution inside the rack, based on the OCP standard 48 V architecture. Higher voltage for the distribution inside the rack is required and 800V (2 or 3 wires) is going to be selected, to be able to reduce the distribution losses and the required copper. As a fundamental element of the new architecture, a high power dense isolated 16:1 DC/DC converts 800V down to 48V now, to quickly reuse most of the available ecosystem. As a technology enabler, mid-voltage GaN plays a relevant role on the primary side, enabling the increase of switching frequency while granting efficiency performance. The LLC Direct Current Transformer (DCX) topology, operating open-loop at constant fs can provide tightly unregulated 48V output with an efficiency of 98%. In this paper a detailed analysis of that converter will be described together with the key components enabling performance in control, drive and active switches. Another area where GaN will play an enabling role for the architecture is the newly defined End Equipment of Sidecar Rack, where the 3-Phase AC to high voltage DC conversion is implemented. Mid voltage Bidirectional GaN will realize topology simplification in front-end rectification. Evolution of the architecture will continue across the next generations of xPUs in line with higher power requirements
