Integrated 2Amp MOSFET & sense resistor provides compact hot swap solution
Linear Technology introduces the LTC4217, a 2A integratedHotSwapcontroller for protecting low power boards with loadsupplyvoltagesranging from 2.9V to 26.5V. Like other Hot Swapdevices,the LTC4217allows a board to be safely inserted and removedfrom alivebackplane by limiting the amount of inrush current totheloadsupply during power up. Hot Swap controllers typically callforanumber of supporting components. However, the LTC4217integratesapower MOSFET and sense resistor in its power path tolimitinrushcurrent, thereby drastically reducing the numberofexternalcomponents required. The device’s internal dV/dTcircuitmeansthere is no need for an external gate capacitor.Anadjustablecurrent limit allows users to vary the currentlimitthresholdunder different loading conditions, for example indiskdrivespin-up to normal operation. This high levelofintegrationpackaged in a tiny DFN makes the LTC4217 aconvenientHot Swapsolution in applications where board real estateis atapremium.
The LTC4217 is suitable for a wide range of RAID, server,telecomandindustrial applications, especially in compactboardsutilizingtechnologies like Fibre Channel, where power istypicallylimitedto less than 25W due to their small size andinability todissipatelarge amounts of heat. The LTC4217 Hot Swapoperationandintegration was designed with these considerations inmind.Duringstart-up, inrush currents are controlled by limiting thegateramprate to a safe 0.3V/ms. Load current is monitored usingthevoltagesensed across the internal 7.5mohm sense resistorandadjusting theinternal 25mohm MOSFET gate-to-sourcevoltageaccordingly. Aseparate ISET pin allows one to adjust the2%accurate (2A) currentlimit threshold during startup andnormaloperation as needed.Meanwhile, current foldback andpower-goodcircuitry ensure thatthe switch is protected fromexcessive loadcurrent and indicatewhether or not healthy powerconditions aremaintained. The LTC4217also features current,temperature and faultoutputs, 2% accurateovervoltage andundervoltage protection, and anadjustable currentlimit timer. Adedicated 12V version (LTC4217-12)is alsoavailable, which containspreset 12V-specificthresholds.
The LTC4217 is offered in commercial andindustrialversions,supporting operating temperature ranges from 0°Cto 70°Cand -40°Cto 85°C, respectively. The LTC4217 can be orderedineither a small16-pin 5mm x 3mm QFN package or a 20-lead TSSOP,bothof which areRoHS compliant.
Posted by Global Electronics
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