Power controller

Linear Technology has introduced the LTC4217, a 2 A integrated Hot Swap controller for protecting low power boards with load supply voltages ranging from 2.9 to 26.5.

The device allows a board to be safely inserted and removed from a live backplane by limiting the amount of inrush current to the load supply during power-up. These controllers typically call for a number of supporting components; however, the device integrates a power MOSFET and sense resistor in its power path to limit inrush current, reducing the number of external components required.

The internal dV/dT circuit means there is no need for an external gate capacitor. An adjustable current limit allows users to vary the current limit threshold under different loading conditions, for example, in disk drive spin-up to normal operation.

The controller is suitable for a wide range of RAID, server, telecom and industrial applications, especially in compact boards using technologies like fibre channel, where power is typically limited to less than 25 W due to their small size and inability to dissipate large quantities of heat.

During start-up, inrush currents are controlled by limiting the gate ramp rate to a safe 0.3 V/ms. Load current is monitored using the voltage sensed across the internal 7.5 mΩ sense resistor and adjusting the internal 25 mΩ MOSFET gate-to-source voltage accordingly.

Meanwhile, current foldback and power-good circuitry ensure that the switch is protected from excessive load current and indicates whether or not healthy power conditions are maintained.

The device also features current, temperature and fault outputs, 2% accurate overvoltage and undervoltage protection and an adjustable current limit timer. A dedicated 12 V version (LTC4217-12) is also available.