AI Server Power
Match rack-bus, IBC, and multiphase VRM stages to the board's load waveform and thermal envelope.
AI Server Power Delivery: Bus, IBC, and VRM
An AI server board links the rack input and hot-swap path to intermediate conversion and point-of-load regulators. The IBC establishes the rail range and available current for downstream VRMs; those regulators must hold the processor or accelerator rail within its specified window as workload demand changes.
Steady-state power does not describe the entire design. Load-step magnitude, slew rate, repetition, permitted droop and overshoot, startup behavior, and cooling all affect the controller, power stages, inductors, capacitors, and protection choices.
Review the input-to-core path together. A change in IBC ratio, switching device, controller, or output network can change the conditions seen by the VRM and the location of conversion losses on the board.
Component Requirements
Typical functions, devices, and parameters in AI Server Power.
| System function | Typical devices | Key parameters | Browse |
|---|---|---|---|
| Rack input and hot-swap Controls connection to the backplane and limits inrush or fault current before board conversion stages. | Hot-swap controllers, pass MOSFETs, eFuses, current-sense amplifiers | Input range, load capacitance, inrush, fault duration, SOA | View category |
| Intermediate bus converter Provides a fixed-ratio or regulated rail between the rack bus and local regulators. | IBC modules, GaN or silicon MOSFETs, gate drivers, controllers | Ratio, isolation, input/output envelope, startup, efficiency | View category |
| Multiphase accelerator VRM Regulates a high-current core rail and responds to the specified processor load waveform. | Multiphase controllers, power stages, inductors, capacitors | Droop, overshoot, phase balance, switching loss, thermal path | View category |
| Current and temperature telemetry Measures rail current and component or board temperature for regulation and fault handling. | Current-sense amplifiers, digital monitors, temperature sensors | Bandwidth, gain error, reporting interface, fault threshold | View category |
Design & Selection Considerations
Accelerator waveform
Use the board or device rail specification for rising and falling load steps, voltage window, event rate, startup, and recovery.
IBC-to-VRM interface
Check the intermediate rail at its minimum and maximum input conditions against VRM operating and absolute limits, including enable timing and fault transitions.
Current sharing and telemetry
Review phase-current balance, reporting accuracy, protection thresholds, and the controller's supported power-stage interface.
Board thermal path
Locate losses in hot-swap, IBC, and VRM stages and relate them to package, copper, airflow, heatsink, and accelerator cooling constraints.
Supply Chain Considerations
Power-stage alternates require controller context
Provide controller and power-stage MPNs, configuration, sensing method, rail target, and firmware dependencies before comparing a replacement.
Transient measurements need a defined setup
Include probe point, bandwidth, load fixture, voltage tolerance, test temperature, and the exact waveform used to qualify the board.
Availability follows the board revision
Separate prototype and production demand and list the approved package, assembly, lifecycle, and date-code constraints for each power-stage position.
Supply Chain Support
Power tree review
Provide the power-tree diagram and BOM grouped by rack input, IBC, VRM, sensing, and protection.
Alternate comparison inputs
Share rail waveform, controller and telemetry requirements, layout or package limits, cooling assumptions, and operating temperature.
Program timing
List quantities and build dates by board revision, plus any vendor approval or lifecycle milestones that constrain substitutions.
Frequently Asked Questions
Provide the starting and ending current, slew rate, event duration and repetition, allowed rail deviation, recovery requirement, and measurement point. Include operating voltage and temperature. A peak-current value without the waveform cannot describe transient response or local energy-storage needs.
Compare the IBC's full output envelope, startup and fault behavior, current capability, and transient response with the VRM's input limits and enable sequence. Then evaluate the combined path with board capacitance and the accelerator load profile; nominal conversion ratio alone is insufficient.
Additional phases can distribute current and switching events, but the result depends on controller limits, phase balance, sensing, inductors, layout, and cooling. Review the rail's transient target and thermal map for the complete multiphase design instead of multiplying a single-stage current rating.