LTC4252B-1/LTC4252B-2
LTC4252C-1/LTC4252C-2
Negative Voltage
Hot Swap Controllers
FEATURES
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DESCRIPTION
The LTC
®
4252 negative voltage Hot Swap
TM
controller
allows a board to be safely inserted and removed from a
live backplane. Output current is controlled by three stages
of current limiting: a timed circuit breaker, active current
limiting and a fast feedforward path that limits peak current
under worst-case catastrophic fault conditions.
Adjustable undervoltage and overvoltage detectors dis-
connect the load whenever the input supply exceeds the
desired operating range. The LTC4252’s supply input is
shunt regulated, allowing safe operation with very high
supply voltages. A multifunction timer delays initial start-
up and controls the circuit breaker’s response time. The
circuit breaker’s response time is accelerated by sensing
excessive MOSFET drain voltage, keeping the MOSFET
within its safe operating area (SOA). An adjustable soft-
start circuit controls MOSFET inrush current at start-up.
The LTC4252-2 provides automatic retry after a fault. The
LTC4252C-1/LTC4252C-2 feature tight ±1% undervoltage/
overvoltage threshold accuracy. The LTC4252 is available
in either an 8-pin or 10-pin MSOP.
The LTC4252B and LTC4252C improve the ruggedness
of the shunt regulator in the LTC4252 and LTC4252A.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
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Allows Safe Board Insertion and Removal from a
Live – 48V Backplane
Floating Topology Permits Very High Voltage Operation
Current Limit With Circuit Breaker Timer
Fast Response Time Limits Peak Fault Current
Programmable Soft-Start Current Limit
Programmable Timer with Drain Voltage
Accelerated Response
±1% Undervoltage/Overvoltage Threshold (LTC4252C)
Improved Ruggedness Shunt Regulator
Adjustable Undervoltage/Overvoltage Protection
LTC4252B-1/LTC4252C-1: Latch Off After Fault
LTC4252B-2/LTC4252C-2: Automatic Retry After Fault
Available in 8-Pin and 10-Pin MSOP Packages
APPLICATIONS
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Hot Board Insertion
Electronic Circuit Breaker
– 48V Distributed Power Systems
Negative Power Supply Control
Central Office Switching
High Availability Servers
ATCA
TYPICAL APPLICATION
–48V/2.5A Hot Swap Controller
–48RTN
R
IN
3× 1.8k IN SERIES
1/4W EACH
D
IN
DDZ13B
**
†
Start-Up Behavior
+
R3
5.1k
*
C
L
100µF
LOAD
EN
V
OUT
GATE
5V/DIV
–48RTN
(SHORT PIN)
C
IN
1µF
V
IN
LTC4252B-1
OV
UV
TIMER
PWRGD
DRAIN
GATE
V
EE
SENSE
R1
402k
1%
SENSE
2.5A/DIV
R
D
1M
Q1
IRF530S
R
C
10
C
C
18nF
R
S
0.02
V
OUT
20V/DIV
R2
32.4k
1%
C1
10nF
C
T
0.33µF
SS
C
SS
68nF
PWRGD
10V/DIV
1ms/DIV
4252B12 TA01a
–48V
4252B12 TA01
* M0C207
**DIODES, INC
†
RECOMMENDED FOR HARSH ENVIRONMENTS
4252b12f
1
LINER [ LINEAR TECHNOLOGY ]
