LT4254 Positive High Voltage Hot Swap Controller with Open-Circuit Detect FEATURES DESCRIPTIO TM Allows Safe Board Insertion and Removal from a The LT 4254 is a high voltage Hot Swap controller that Live Backplane allows a board to be safely inserted and removed from a Controls Supply Voltage from 10.8V to 36V live backplane. An internal driver controls the high side Foldback Current Limiting N-channel MOSFET gate for supply voltages ranging from Open Circuit and Overcurrent Fault Detect 10.8V to 36V. The part features an open-circuit detect Drives an External N-Channel MOSFET (OPEN) output that indicates abnormally low load current Automatic Retry or Latched Off Operation conditions. After Overcurrent Fault The LT4254 features an adjustable analog foldback cur- Programmable Supply Voltage Power-Up Rate rent limit. If the supply remains in current limit for more Undervoltage and Overvoltage Protection than a programmable time, the N-channel MOSFET shuts Open MOSFET Detection off, the PWRGD output goes low and the LT4254 either Available in 16-Lead SSOP Package automatically restarts after a time-out delay or latches off until the UV pin is cycled low. The RETRY pin sets whether U the part will automatically restart after an overcurrent fault APPLICATIO S or if it will latch off until the UV pin is cycled low. Hot Board Insertion The PWRGD output indicates when the output voltage Electronic Circuit Breaker/Power Bussing rises above a programmed level. An external resistor Industrial High Side Switch/Circuit Breaker string from V provides programmable undervoltage and CC 24V Industrial/Alarm Systems overvoltage protection. 12V and 24V Distributed Power 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 24V, 2A Hot Swap Controller R5 Q1 0.025 IRF530 V OUT V IN 24V 24V LT4254 Start-Up Behavior D1 1.5A (SHORT PIN) C CMPZ5241B L 11V R1 V SENSE CC R6 R8 324k V 10 IN 140k 20V/DIV UV GATE CONTACT BOUNCE R7 R4 100 27k V OUT LT4254 C3 20V/DIV R2 C1 0.1F 40.2k 10nF INRUSH OV FB CURRENT R3 R9 500mA/DIV 40.2k 40.2k OPEN RETRY C = 168F L PWRGD PWRGD TIMER PWRGD 20V/DIV C2 4254 TA01 2.5ms/DIV 4245 TA02 GND UV = 20V GND 33nF OV = 40V PWRGD = 18V 4254fb 1 U ULT4254 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART NUMBER Supply Voltage (V ) .................................. 0.3 to 44V CC UV 1 16 V CC SENSE, PWRGD ......................................... 0.3 to 44V OV 2 15 SENSE LT4254CGN GATE .......................................................... 0.3 to 50V NC 3 14 NC LT4254IGN FB, UV, OPEN ............................................. 0.3 to 44V OPEN 4 13 GATE PWRGD 5 12 NC OV .............................................................. 0.3 to 18V NC 6 11 NC RETRY ........................................................ 0.3 to 15V GN PART MARKING 7 RETRY 10 FB TIMER ..................................................... 0.3V to 4.3V GND 8 9 TIMER 4254 Maximum Input Current (TIMER) ....................... 100A GN PACKAGE 4254I Operating Temperature 16-LEAD PLASTIC TSSOP T = 125C, = 130C/W JMAX JA LT4254C ................................................. 0C to 70C Order Options Tape and Reel: Add TR LT4254I ............................................. 40C to 85C Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Storage Temperature Range ................ 65C to 150C Lead Free Part Marking: