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
LTC4252B-1/LTC4252B-2
LTC4252C-1/LTC4252C-2
ABSOLUTE MAXIMUM RATINGS
All Voltages Referred to V
EE
(Note 1)
Current into V
IN
(100µs Pulse) .............................100mA
V
IN
, DRAIN Pin Minimum Voltage ........................ – 0.3V
Input/Output Pins
(Except SENSE and DRAIN) Voltage .......... –0.3V to 16V
SENSE Pin Voltage .................................... –0.6V to 16V
Current Out of SENSE Pin (20µs Pulse) .......... –200mA
Current into DRAIN Pin (100µs Pulse) ...................20mA
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range
LTC4252BC-1/LTC4252BC-2
LTC4252CC-1/LTC4252CC-2 .................... 0°C to 70°C
LTC4252BI-1/LTC4252BI-2
LTC4252CI-1/LTC4252CI-2 ................. –40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
PIN CONFIGURATION
TOP VIEW
V
IN
SS
SENSE
V
EE
1
2
3
4
8
7
6
5
TIMER
UV/OV
DRAIN
GATE
TOP VIEW
V
IN
PWRGD
SS
SENSE
V
EE
1
2
3
4
5
10
9
8
7
6
TIMER
UV
OV
DRAIN
GATE
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC4252BCMS8-1#PBF
LTC4252BCMS8-2#PBF
LTC4252BIMS8-1#PBF
LTC4252BIMS8-2#PBF
LTC4252BCMS-1#PBF
LTC4252BCMS-2#PBF
LTC4252BIMS-1#PBF
LTC4252BIMS-2#PBF
LTC4252CCMS-1#PBF
LTC4252CCMS-2#PBF
LTC4252CIMS-1#PBF
LTC4252CIMS-2#PBF
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
LTC4252BCMS8-1#TRPBF LTGDX
LTC4252BCMS8-2#TRPBF LTGDZ
LTC4252BIMS8-1#TRPBF
LTC4252BIMS8-2#TRPBF
LTC4252BCMS-1#TRPBF
LTC4252BCMS-2#TRPBF
LTC4252BIMS-1#TRPBF
LTC4252BIMS-2#TRPBF
LTC4252CCMS-1#TRPBF
LTC4252CCMS-2#TRPBF
LTC4252CIMS-1#TRPBF
LTC4252CIMS-2#TRPBF
LTGDX
LTGDZ
LTGDY
LTGFB
LTGDY
LTGFB
LTGFC
LTGFD
LTGFC
LTGFD
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
4252b12f
2
LTC4252B-1/LTC4252B-2
LTC4252C-1/LTC4252C-2
ELECTRICAL CHARACTERISTICS
SYMBOL
V
Z
r
Z
I
IN
V
LKO
V
LKH
V
CB
V
ACL
V
ACL
/
V
CB
V
FCL
V
SS
R
SS
I
SS
PARAMETER
V
IN
– V
EE
Zener Voltage
V
IN
– V
EE
Zener Dynamic Impedance
V
IN
Supply Current
V
IN
Undervoltage Lockout
V
IN
Undervoltage Lockout Hysteresis
Circuit Breaker Current Limit Voltage
Analog Current Limit Voltage
Analog Current Limit Voltage/
Circuit Breaker Voltage
Fast Current Limit Voltage
SS Voltage
SS Output Impedance
SS Pin Current
UV = OV = 4V, V
SENSE
= V
EE
,
V
SS
= 0V (Sourcing)
UV = OV = 0V, V
SENSE
= V
EE
,
V
SS
= 2V (Sinking)
V
OS
Analog Current Limit Offset Voltage
V
ACL
+V
OS
/ Ratio (V
ACL
+ V
OS
) to SS Voltage
V
SS
I
GATE
GATE Pin Output Current
UV = OV = 4V, V
SENSE
= V
EE
,
V
GATE
= 0V (Sourcing)
UV = OV = 4V, V
SENSE
– V
EE
= 0.15V,
V
GATE
= 3V (Sinking)
UV = OV = 4V, V
SENSE
– V
EE
= 0.3V,
V
GATE
= 1V (Sinking)
V
GATE
V
GATEH
V
GATEL
V
UVHI
V
UVLO
V
UV
V
UVHST
V
OVHI
V
OVLO
V
OV
V
OVHST
I
SENSE
I
INP
V
TMRH
V
TMRL
External MOSFET Gate Drive
Gate High Threshold
Gate Low Threshold
UV Pin Threshold HIGH
UV Pin Threshold LOW
UV Pin Threshold
UV Pin Hysteresis
OV Pin Threshold HIGH
OV Pin Threshold LOW
OV Pin Threshold
OV Pin Hysteresis
SENSE Pin Input Current
UV, OV Pin Input Current
TIMER Pin Voltage High Threshold
TIMER Pin Voltage Low Threshold
Low-to-High Transition
(
●
for LTC4252C Only)
UV = OV = 4V, V
SENSE
= 50mV
UV = OV = 4V
Low-to-High Transition
(
●
for LTC4252C Only)
V
GATE
– V
EE
, I
IN
= 2mA
V
GATEH
= V
IN
– V
GATE
, I
IN
= 2mA,
for
PWRGD
Status (MS Only)
(Before Gate Ramp-Up)
●
3.075
●
2.775
●
●
●
●
●
●
●
●
●
●
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
CONDITIONS
I
IN
= 2mA
I
IN
= 2mA to 30mA
UV = OV = 4V, V
IN
= (V
Z
– 0.3V)
Coming Out of UVLO (Rising V
IN
)
V
CB
= (V
SENSE
– V
EE
)
V
ACL
= (V
SENSE
– V
EE
),
SS = Open or 2.2V
V
ACL
= (V
SENSE
– V
EE
),
SS = Open or 1.4V
V
FCL
= (V
SENSE
– V
EE
)
After End of SS Timing Cycle
●
●
l
LTC4252B-1/-2
MIN
TYP MAX
11.5
13
5
0.8
9.2
1
●
●
●
●
LTC4252C-1/-2
MIN
TYP MAX
11.5
13
5
0.9
9
0.5
45
50
14.5
2
10
55
UNITS
V
Ω
mA
V
V
mV
mV
14.5
2
11.5
60
120
40
80
50
100
1.05
150
200
2.2
100
22
28
10
0.05
40
58
17
190
10
12
2.8
0.5
3.225 3.375
2.925 3.075
3.05
300
5.85
5.25
6.15
5.55
600
–15
± 0.1
4
1
–30
±1
6.45
5.85
5.04
82
292
V
Z
10
80
40
300
150
1.20
200
1.4
50
28
28
10
0.05
58
17
190
12
2.8
0.5
1.38
300
V/V
mV
V
kΩ
µA
mA
mV
V/V
80
µA
mA
mA
V
Z
V
V
V
V
V
3.08
324
3.11
356
V
mV
V
V
5.09
102
–15
± 0.1
4
1
5.14
122
–30
±1
V
mV
µA
µA
V
V
4252b12f
3
LTC4252B-1/LTC4252B-2
LTC4252C-1/LTC4252C-2
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
SYMBOL
I
TMR
PARAMETER
TIMER Pin Current
CONDITIONS
Timer On (Initial Cycle/Latchoff/
Shutdown Cooling, Sourcing),
V
TMR
= 2V
Timer Off (Initial Cycle, Sinking),
V
TMR
= 2V
Timer On (Circuit Breaker, Sourcing,
I
DRN
= 0µA), V
TMR
= 2V
Timer On (Circuit Breaker, Sourcing,
I
DRN
= 50µA), V
TMR
= 2V
Timer Off (Circuit Breaker/
Shutdown Cooling, Sinking),
V
TMR
= 2V
∆I
TMRACC
/ [(I
TMR
at I
DRN
= 50µA) – (I
TMR
at I
DRN
=
0µA)]/∆I
DRN
∆I
DRN
V
DRNL
I
DRNL
V
DRNCL
V
PGL
I
PGH
t
SS
DRAIN Pin Voltage Low Threshold
DRAIN Leakage Current
DRAIN Pin Clamp Voltage
PWRGD
Output Low Voltage
PWRGD
Pull-Up Current
SS Default Ramp Period
Timer On (Circuit Breaker with
I
DRN
= 50µA)
For
PWRGD
Status (MS Only)
V
DRAIN
= 5V (4V for LTC4252C)
I
DRN
= 50µA
I
PG
= 1.6mA (MS Only)
I
PG
= 5mA (MS Only)
V
PWRGD
= 0V (Sourcing) (MS Only)
SS Pin Floating, V
SS
Ramps from
0.2V to 2V
SS Pin Floating, V
SS
Ramps from
0.1V to 0.9V
t
PLLUG
t
PHLOG
UV Low to Gate Low
OV High to Gate Low
0.4
0.4
●
●
●
ELECTRICAL CHARACTERISTICS
LTC4252B-1/-2
MIN
TYP MAX
5.8
LTC4252C-1/-2
MIN
TYP MAX
5.8
UNITS
µA
28
230
630
5.8
28
230
630
5.8
mA
µA
µA
µA
8
2.385
± 0.1
7
0.2
40
58
180
0.4
1.1
80
40
±1
8
2.385
± 0.1
6
0.2
58
0.4
1.1
80
±1
µA/µA
V
µA
V
V
V
µA
µs
230
0.4
0.4
µs
µs
µs
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to V
EE
unless otherwise
specified.
4252b12f
4
LTC4252B-1/LTC4252B-2
LTC4252C-1/LTC4252C-2
TYPICAL PERFORMANCE CHARACTERISTICS
14.5
V
Z
vs Temperature
I
IN
= 2mA
10
9
r
Z
vs Temperature
I
IN
= 2mA
2000
1800
1600
1400
I
IN
(µA)
1200
1000
800
600
400
200
I
IN
vs Temperature
V
IN
= (V
Z
– 0.3V)
14.0
8
7
r
Z
( )
6
5
4
3
13.5
V
Z
(V)
13.0
12.5
12.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252B12 G01
2
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252B12 G02
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252B12 G03
I
IN
vs V
IN
1000
Undervoltage Lockout V
LKO
vs Temperature
12.0
11.5
1.5
1.3
Undervoltage Lockout Hysteresis
V
LKH
vs Temperature
100
V
LKO
(V)
I
IN
(mA)
11.0
10.5
V
LKH
(V)
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252B12 G05
1.1
10
10.0
9.5
9.0
8.5
8.0
–55 –35 –15
0.9
0.7
0.5
–55 –35 –15
1
0.1
125°C
85°C
25°C
–40°C
0
2
4
6
8 10 12 14 16 18 20 22
V
IN
(V)
4252B12 G04
5 25 45 65 95 105 125
TEMPERATURE (°C)
4252B12 G06
60
58
56
54
Circuit Breaker Current Limit
Voltage V
CB
vs Temperature
120
115
110
V
ACL
(mV)
Analog Current Limit Voltage
V
ACL
vs Temperature
Fast Current Limit Voltage V
FCL
vs Temperature
300
275
250
V
FCL
(mV)
225
200
175
150
–55 –35 –15
V
CB
(mV)
52
50
48
46
44
42
40
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252B12 G07
105
100
95
90
85
80
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252B12 G08
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252B12 G09
4252b12f
5
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