Linear Technology Launches Integrated 2Amp MOSFET & Sense Resistor

Linear Technology Corporation has introduced its LTC4217, a 2A integrated Hot Swap controller for protecting low power boards with load supply voltages ranging from 2.9V to 26.5V. Like other Hot Swap devices, the LTC4217 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. Hot Swap controllers typically call for a number of supporting components. However, the LTC4217 integrates a power MOSFET and sense resistor in its power path to limit inrush current, thereby drastically reducing the number of external components required. The device’s internal dV/dT circuit means there is no need for an external gate capacitor.



The LTC4217 Hot Swap operation and integration was designed with these considerations in mind. During start-up, inrush currents are controlled by limiting the gate ramp rate to a safe 0.3V/ms. The Load current is monitored using the voltage sensed across the internal 7.5mohm sense resistor and adjusting the internal 25mohm MOSFET gate-to-source voltage accordingly. A separate ISET pin allows one to adjust the 2% accurate (2A) current limit threshold during startup and normal operation as needed. The LTC4217 also features current, temperature and fault outputs, 2% accurate overvoltage and undervoltage protection, and an adjustable current limit timer. A dedicated 12V version (LTC4217-12) is also available, which contains preset 12V-specific thresholds. The LTC4217 is offered in commercial and industrial versions, supporting operating temperature ranges from 0°C to 70°C and -40°C to 85°C, respectively. The LTC4217 can be ordered in either a small 16-pin 5mm x 3mm QFN package or a 20-lead TSSOP, both of which are RoHS compliant. The devices are priced starting at $3.35 each in 1,000 piece quantities and are available today in production quantities.