LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
Negative Voltage
Hot Swap Controllers
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FEATURES
DESCRIPTIO
■
Allows Safe Board Insertion and Removal from a
The LTC®4252 negative voltage Hot SwapTM controller
allows a board to be safely inserted and removed from a
livebackplane.Outputcurrentiscontrolledbythreestages
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.
Live –48V Backplane
■
Floating Topology Permits Very High Voltage
Operation
■
Programmable Analog Current Limit With Circuit
Breaker Timer
■
Fast Response Time Limits Peak Fault Current
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.
■
Programmable Soft-Start Current Limit
■
Programmable Timer with Drain Voltage
Accelerated Response
■
±1% Undervoltage/Overvoltage Threshold Accuracy
(LTC4252A)
■
Adjustable Undervoltage/Overvoltage Protection
■
LTC4252-1/LTC4252A-1: Latch Off After Fault
■
LTC4252-2: Automatic Retry After Fault
■
Available in 8-Pin and 10-Pin MSOP Packages
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TheLTC4252-1/LTC4252A-1latchoffafteracircuitbreaker
fault times out. The LTC4252-2 provides automatic retry
after a fault. The LTC4252A-1/LTC4252A-2 feature tight
±1% undervoltage/overvoltage threshold accuracy. The
LTC4252 is available in either an 8-pin or 10-pin MSOP.
APPLICATIO S
■
Hot Board Insertion
■
Electronic Circuit Breaker
■
–48V Distributed Power Systems
■
Negative Power Supply Control
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
■
Central Office Switching
■
High Availability Servers
■
ATCA
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TYPICAL APPLICATIO
Start-Up Behavior
–48V/2.5A Hot Swap Controller
GND
R
IN
+
3× 1.8k IN SERIES
C
L
GATE
1/4W EACH
100µF
LOAD
EN
5V/DIV
C
IN
1µF
R3
GND
5.1k
(SHORT PIN)
V
R1
402k
1%
IN
LTC4252-1
PWRGD
SENSE
2.5A/DIV
V
OUT
*
OV
R
D
1M
UV
DRAIN
GATE
R2
32.4k
1%
Q1
IRF530S
V
OUT
TIMER
SS
20V/DIV
C
T
SENSE
V
EE
0.33µF
R
R
S
0.02Ω
C
C1
10nF
C
10Ω
C
SS
68nF
C
18nF
PWRGD
10V/DIV
4252-1/2 TA01
–48V
1ms/DIV
4252-1/2 TA01a
* M0C207
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