The ADM1177 from Analog Devices is a Hot Swap Controller and Digital Power Monitor IC that has been designed to allow safe board insertion and removal from a live backplane. It requires an input voltage of 3.15 - 16.5 V and an input current from -100 nA to +100 nA. This eFuse IC consists of a 12-bit analog-to-digital converter (ADC), FET drive controller, comparator, current sense amplifier, multiplexer, and a serial interface. It measures the voltage across the sense resistor using the built-in current sense amplifier and communicates the values via an I²C interface using a 12-bit ADC. This controller IC limits the current using this resistor by controlling the gate voltage of an external N-channel FET in the power path and keeping the voltage across the sense resistor below a preset maximum. It protects the external FET by limiting the time (set using a capacitor attached to the TIMER pin) that the maximum current flows through it.

This hot swap controller IC integrates a soft start pin that gives the user control over the reference on the current sense amplifier. It has an internal current source that charges the capacitor on the soft start pin during start-up, allowing the user to set the profile of the initial current ramp. This controller not only supports up to four unique I²C addresses but also provides fast response time at a rate of 400 kHz (fast-mode compliant interface). It is available in a surface-mount package that measures 3.10 x 5.15 mm and is ideal for central office equipments, telecommunications and data communications equipment, power monitoring, and PC/Server applications.