The MAX17009 is a 2-phase, step-down interleaved, fixed-frequency controller for AMD's serial VID interface (SVI) CPU core supplies. Power-on detection of the CPU configures the MAX17009 as two independent single-phase regulators for a dual CPU core application, or one high-current, dual-phase, combined-output regulator for a unified core application. A reference buffer output (NBV_BUF) sets the voltage-regulation level for a North Bridge (NB) regulator, completing the total CPU cores and NB power requirements. The MAX17009 is fully AMD SVI compliant. Output voltages are dynamically changed through a 2-wire serial interface, allowing the switching regulator and the reference buffer to be individually programmed to different voltages. A programmable slew-rate controller enables controlled transitions between VID codes, soft-start limits the inrush current, and soft-shutdown brings the output voltage back down to zero without any negative ring. Transient phase repeat improves the response of the fixed-frequency architecture. Independently programmable AC and DC droop and selectable offset improve stability and reduce the total output-capacitance requirement. A thermistor-based temperature sensor allows for a programmable thermal-fault output (VRHOT). The MAX17009 includes thermal-fault protection, undervoltage protection (UVP), and selectable output overvoltage protection (OVP). When any of these protection features detect a fault, the controller shuts down. True differential current sensing improves current limit, load-line accuracy, and current balance when operating in combined mode. The MAX17009 has an adjustable switching frequency, allowing 100kHz to 1.2MHz per-phase operation.