LT4256-1/LT4256-2 Positive High Voltage Hot Swap Controllers FEATURES DESCRIPTIO TM Allows Safe Board Insertion and Removal from a The LT 4256-1/LT4256-2 are high voltage Hot Swap Live Backplane controllers that allow a board to be safely inserted and Controls Supply Voltage from 10.8V to 80V removed from a live backplane. An internal driver drives an Foldback Current Limiting external N-channel MOSFET switch to control supply Overcurrent Fault Detection voltages ranging from 10.8V to 80V. Drives an External N-Channel MOSFET The LT4256-1/LT4256-2 features an adjustable analog Programmable Supply Voltage Power-Up Rate foldback current limit. If the supply remains in current limit Undervoltage Protection for more than a programmable time, the N-channel Latch Off Operation Mode (LT4256-1) MOSFET shuts off and the PWRGD output asserts low. The Automatic Retry (LT4256-2) LT4256-2 automatically restarts after a time-out delay. Available in an 8-Pin SO Package The LT4256-1 latches off until the UV pin is cycled low. U The PWRGD output indicates when the output voltage APPLICATIO S rises above a programmed level. An external resistor string from V provides programmable undervoltage CC Hot Board Insertion protection. Electronic Circuit Breaker/Power Bussing Industrial High Side Switch/Circuit Breaker The LT4256 can be used as an upgrade to LT1641 designs. 24V/48V Industrial/Alarm Systems See Table 1 on page 14 for upgraded specifications. Ideally Suited for 12V, 24V and 48V Distributed The LT4256-1 and LT4256-2 are available in an 8-pin SO Power Systems package that is pin compatible with the LT1641. 48V Telecom Systems , LTC and LT are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO 48V, 2A Hot Swap Controller LT4256 Start-Up Behavior 0.02 IRF530 V OUT V IN 48V 48V SMAT70A 2A CMPZ5241B C L 11V (SHORT PIN) V IN 87 50V/DIV 10 36.5k 27k V SENSE CC 64.9k 10nF 100 1 6 V OUT UV GATE 50V/DIV LT4256-1/ 0.1F LT4256-2 8.06k 4.02k INRUSH 2 CURRENT FB 500mA/DIV 3 PWRGD C = 225F L PWRGD PWRGD 50V/DIV 4256 TA01 5 UV = 36V 2.5ms/DIV 4256 TA02 TIMER GND PWRGD = 40V GND 33nF 4 425612fa 1 U ULT4256-1/LT4256-2 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART Supply Voltage (V ) ................................ 0.3 to 100V CC NUMBER SENSE, PWRGD ....................................... 0.3 to 100V LT4256-1CS8 GATE (Note 2) ................................ 0.3V to V + 10V CC TOP VIEW LT4256-1IS8 Maximum Input Current (GATE) ......................... 200A UV 1 8 V LT4256-2CS8 FB, UV ........................................................ 0.3 to 44V CC FB 2 7 SENSE LT4256-2IS8 TIMER ..................................................... 0.3V to 4.3V PWRGD 3 6 GATE Maximum Input Current (TIMER) ....................... 100A S8 PART MARKING GND TIMER 4 5 Operating Temperature 42561 LT4256C ................................................. 0C to 70C S8 PACKAGE 42561I 8-LEAD PLASTIC SO LT4256I ............................................. 40C to 85C 42562 T = 125C, = 110C/W JMAX JA Storage Temperature Range ................ 65C to 150C 42562I Lead Temperature (Soldering, 10 sec)................. 300C Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: