Hot-Swap Controller Delivers 2.9V to 15V Load Supply Voltages

Sept. 16, 2010
The LTC4219 5A hot-swap controller protects low-power boards with load supply voltages ranging from 2.9V to 15V

The LTC4219 5A hot-swap controller protects low-power boards with load supply voltages ranging from 2.9V to 15V. With the controller, developed by Linear Technology, a board can be safely inserted and removed from a live backplane.

Hot-swap controllers typically call for a number of supporting components. However, the LTC4219 integrates a power MOSFET and sense resistor in its power path to limit inrush current, reducing the number of external components required. The device's internal dV/dt circuit means there’s no need for an external gate capacitor. An adjustable current limit allows users to vary the current-limit threshold under different loading conditions, such as in disk-drive spin-up to normal operation. Such integration packaged in a tiny DFN suits the LTC4219 for space-constrained applications.

For instance, the controller will find homes in a range of RAID, server, telecom, and industrial applications. Particularly good fits are compact boards using technologies like Fibre Channel, where power is typically limited to less than 25W due to their small size and inability to dissipate large amounts of heat. During startup, inrush currents are controlled by limiting the gate ramp rate to a safe 0.3V/ms. Load current is monitored using the voltage sensed across the internal 7.5mΩ sense resistor and adjusting the internal 33mΩ MOSFET gate-to-source voltage accordingly.

A separate ISET pin enables adjustment of the 10% accurate (5A) current-limit threshold during startup and normal operation as needed. In addition, current foldback and power-good circuitry protect the switch from excessive load current and indicate whether or not healthy power conditions are maintained. The LTC4219 also features current, temperature, and fault outputs, as well as an adjustable current-limit timer.

The LTC4219 is available as a dedicated 12V (LTC4219-12) or 5V (LTC4219-5) version, which contain preset 12V/5V-specific thresholds.

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