LTC4252-2_15 Datasheet, PDF (1/36 Pages) Linear Technology – Negative Voltage Hot Swap Controllers

LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
Negative Voltage
Hot Swap Controllers
Features
n _{Allows Safe Board Insertion and Removal from a}
Live – 48V Backplane
n _{Floating Topology Permits Very High Voltage Operation}
n _{Current Limit With Circuit Breaker Timer}
n _{Fast Response Time Limits Peak Fault Current}
n _{Programmable Soft-Start Current Limit}
n _{Programmable Timer with Drain Voltage}
Accelerated Response
n _{±1% Undervoltage/Overvoltage Threshold Accuracy}
(LTC4252A)
■ _{Adjustable Undervoltage/Overvoltage Protection}
■ _{LTC4252-1/LTC4252A-1: Latch Off After Fault}
■ _{LTC4252-2/LTC4252A-2: Automatic Retry After Fault}
■ _{Available in 8-Pin and 10-Pin MSOP Packages}
Applications
n _{Hot Board Insertion}
n _{Electronic Circuit Breaker}
n _{– 48V Distributed Power Systems}
n _{Negative Power Supply Control}
n _{Central Office Switching}
n _{High Availability Servers}
n _ATCA
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 LTC4252-1/LTC4252A-1 latch off after a circuit breaker
fault times out. The LTC4252-2/LTC4252A-2 provide au-
tomatic 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, while the LTC4252A is available in the
10-pin MSOP.
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.
Typical Application
–48RTN
–48RTN
(SHORT PIN)
R1
402k
1%
R2
32.4k
1%
–48V/2.5A Hot Swap Controller
R_IN
3× 1.8k IN SERIES
1/4W EACH
+ _CL
100µF
C1
10nF
DD_IDNZ^†_13B**
C_T
0.33µF
V_IN
LTC4252-1
OV
PWRGD
UV
DRAIN
TIMER
GATE
SS V_EE SENSE
C_SS
68nF
C_IN R3
1µF 5.1k
*
R_D 1M
LOAD
EN
V_OUT
Q1
IRF530S
R_C
10Ω
C_C
18nF
R_S
0.02Ω
– 48V
* M0C207
**DIODES, INC
†_{RECOMMENDED FOR HARSH ENVIRONMENTS}
425212 TA01
GATE
5V/DIV
SENSE
2.5A/DIV
V_OUT
20V/DIV
PWRGD
10V/DIV
For more information www.linear.com/LTC4252-1
Start-Up Behavior
1ms/DIV
425212 TA01a
425212fe
1