Hot swap controller with PMBus telemetry
The ADM1278-1BCPZ is a hot swap controller and monitor from Analog Devices, designed to manage inrush current and provide fault protection for a single 4.5 V to 20 V rail. It integrates a PMBus interface for real-time current, voltage, and power telemetry, letting a system controller read the load status without separate sense circuitry. Because it lacks an internal switch, the external FET and sense resistor sit between the input supply and the load — the controller drives the gate, monitors the drop across the sense element, and reports back over the PMBus. This external-FET architecture means the board designer picks the FET Rds(on) and current rating to match the load, not the controller's internal limit.
Supply range and programmable protection
The controller draws 5.5 mA from that rail, so the power budget impact on the upstream converter is under 110 mW at 20 V. Programmable features include UVLO, OVP, current limit, fault timeout, slew rate control, auto retry, and latched fault. The UVLO and OVP thresholds set the window the input rail must stay within; the slew rate pin capacitor controls how fast the gate turns on, which directly sets the inrush current profile. Auto retry is useful for loads that recover after a transient fault — a latched fault is better for loads where a persistent short should stay off until cleared.