LTC4252-1 Datasheet, PDF (1/32 Pages) Linear Technology – Negative Voltage Hot Swap Controllers

LTC4252-1/LTC4252-2
Negative Voltage
Hot Swap Controllers
FEATURES
s _{Allows Safe Board Insertion and Removal from a}
Live – 48V Backplane
s _{Floating Topology Permits Very High Voltage}
Operation
s _{Programmable Analog Current Limit With Circuit}
Breaker Timer
s _{Fast Response Time Limits Peak Fault Current}
s _{Programmable Soft-Start Current Limit}
s _{Programmable Timer with Drain Voltage}
Accelerated Response
s _{Programmable Undervoltage/Overvoltage Protection}
s _{LTC4252-1: Latch Off After Fault}
s _{LTC4252-2: Automatic Retry After Fault}
U
APPLICATIO S
s _{Hot Board Insertion}
s _{Electronic Circuit Breaker}
s _{– 48V Distributed Power Systems}
s _{Negative Power Supply Control}
s _{Central Office Switching}
s _{Programmable Current Limiting Circuit}
s _{High Availability Servers}
s _{Disk Arrays}
DESCRIPTIO
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.
Programmable undervoltage and overvoltage detectors
disconnect 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). A programmable
soft-start circuit controls MOSFET inrush current at start-
up. A power good status output can enable a power
module at start-up or disable it if the circuit breaker trips.
The LTC4252-1 latches off after a circuit breaker fault times
out. The LTC4252-2 provides automatic retry after a fault.
The LTC4252 is available in either an 8-pin or 10-pin MSOP.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
GND
GND
(SHORT PIN)
R1
402k
1%
R2
32.4k
1%
– 48V
* M0C207
– 48V/2.5A Hot Swap Controller
R_IN
3× 1.8k IN SERIES
1/4W EACH
+ _CL
100µF
1
V_IN
LTC4252-1
8
OV
2
PWRGD
9
UV
7
DRAIN
10
TIMER
6
GATE
C_T
3
0.33µF
SS
4
V_EE SENSE
C1
C_SS
5
10nF
68nF
C_IN
1µF
R3
5.1k
*
R_D 1M
R_C
10Ω
C_C
18nF
LOAD
EN
V_OUT
Q1
IRF530S
R_S
0.02Ω
4252-1/2 TA01
GATE
5V/DIV
SENSE
2.5A/DIV
V_OUT
20V/DIV
PWRGD
10V/DIV
Start-Up Behavior
1ms/DIV
4252-1/2 TA01a
425212f
1