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: