LTC4251/LTC4251-1/
LTC4251-2
Negative Voltage
Hot Swap Controllers in SOT-23
FEATURES
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DESCRIPTION
The
LTC
®
4251/LTC4251-1/LTC4251-2
negative voltage
Hot Swap™ controllers allow a board to be safely inserted
and removed from a live backplane. Output current is con-
trolled 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 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 LTC4251 UV/OV thresholds are designed to match the
standard telecom operating range of – 43V to –75V. The
LTC4251-1 UV/OV thresholds extend the operating range
to encompass –36V to –72V. The LTC4251-2 implements
a UV threshold of –43V only.
All parts are available in the 6-Pin SOT-23 package.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
Hot Swap and ThinSOT are trademarks 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
Programmable Analog Current Limit with Circuit
Breaker Timer
Fast Response Time Limits Peak Fault Current
Programmable Timer
Programmable Undervoltage/Overvoltage Protection
Low Profile (1mm) ThinSOT™ Package
APPLICATIONS
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Hot Board Insertion
Electronic Circuit Breaker
–48V Distributed Power Systems
Negative Power Supply Control
Central Office Switching
Programmable Current Limiting Circuit
High Availability Servers
Disk Arrays
TYPICAL APPLICATION
–48V, 2.5A Hot Swap Controller
–48RTN
–48RTN
(SHORT PIN)
R1
402k
1%
C1
10nF
R2
32.4k
1%
–48V
*TWO 0.25W RESISTORS IN SERIES FOR
R
IN
ON THE PCB ARE RECOMMENDED.
**DIODES, INC.
†RECOMMENDED FOR HARSH ENVIRONMENTS
R
IN
*
10k
500mW
D
IN†
DDZ13B**
V
IN
UV/OV
GATE
3
R
C
10
C
C
18nF
LTC4251
TIMER SENSE
V
EE
C
T
150nF
1
R
S
0.02
2
425112 TA01
Start-Up Behavior
C
L
100µF
C
IN
1µF
+
LOAD
V
OUT
Q1
IRF530S
GATE
5V/DIV
SENSE
2.5A/DIV
V
OUT
20V/DIV
4
1ms/DIV
425112 TA02
425112fd
For more information
www.linear.com/4251
1
LTC4251/LTC4251-1/
LTC4251-2
ABSOLUTE MAXIMUM RATINGS
(Note 1), All Voltages are Referred to V
EE
PIN CONFIGURATION
Current into V
IN
(100µs Pulse) .............................100mA
Minimum V
IN
Voltage ............................................ – 0.3V
Gate, UV/OV, Timer Voltage........................ –0.3V to 16V
Sense Voltage ............................................ –0.6V to 16V
Current Out of Sense Pin (20µs Pulse).............. –200mA
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range
LTC4251C/LTC4251-1C/LTC4251-2C ........ 0°C to 70°C
LTC4251I/LTC4251-1I/LTC4251-2I........–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
TOP VIEW
SENSE 1
V
EE
2
V
IN
3
6 GATE
5 UV/OV*
4 TIMER
S6 PACKAGE
6-LEAD PLASTIC SOT-23
*UV FOR LTC4251-2
T
JMAX
= 125°C,
θ
JA
= 256°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC4251CS6#PBF
LTC4251IS6#PBF
LTC4251-1CS6#PBF
LTC4251-1IS6#PBF
LTC4251-2CS6#PBF
LTC4251-2IS6#PBF
TAPE AND REEL
LTC4251CS6#TRPBF
LTC4251IS6#TRPBF
LTC4251-1CS6#TRPBF
LTC4251-1IS6#TRPBF
LTC4251-2CS6#TRPBF
LTC4251-2IS6#TRPBF
PART MARKING
LTUQ
LTUR
LTQU
LTQV
LTK6
LTAAZ
PACKAGE DESCRIPTION
6-Lead Plastic SOT-23
6-Lead Plastic SOT-23
6-Lead Plastic SOT-23
6-Lead Plastic SOT-23
6-Lead Plastic SOT-23
6-Lead Plastic SOT-23
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 2, 3)
SYMBOL PARAMETER
V
Z
r
Z
I
IN
V
LKO
V
LKH
V
CB
V
ACL
V
FCL
I
GATE
V
GATE
V
IN
to V
EE
Zener Voltage
V
IN
to 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
Fast Current Limit Voltage
GATE Pin Output Current
V
CB
= (V
SENSE
– V
EE
)
V
ACL
= (V
SENSE
– V
EE
)
V
FCL
= (V
SENSE
– V
EE
)
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
EE
, I
IN
= 2mA
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l
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ELECTRICAL CHARACTERISTICS
I
IN
= 2mA
CONDITIONS
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MIN
11.5
TYP
13
5
0.8
9.2
1
MAX
14.5
2
11.5
60
120
300
80
UNITS
V
Ω
mA
V
V
mV
mV
mV
µA
mA
mA
V
425112fd
I
IN
= 2mA to 30mA
UV/OV = 4V, V
IN
= (V
Z
– 0.3V)
Coming Out of UVLO (Rising V
IN
)
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40
80
150
40
50
100
200
58
17
190
12
External MOSFET Gate Drive
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10
V
Z
2
For more information
www.linear.com/4251
LTC4251/LTC4251-1/
LTC4251-2
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
SYMBOL PARAMETER
V
GATEL
V
UVHI
V
UVLO
V
UVHST
V
OVHI
V
OVLO
V
OVHST
I
SENSE
I
INP
V
TMRH
V
TMRL
I
TMR
Gate Low Threshold
UV Threshold High
UV Threshold Low
UV Hysteresis
OV Threshold High
OV Threshold Low
OV Hysteresis
SENSE Input Current
UV/OV Input Current
Timer Voltage High Threshold
Timer Voltage Low Threshold
Timer Current
Timer On (Initial Cycle, Sourcing), V
TMR
= 2V
Timer Off (Initial Cycle, Sinking), V
TMR
= 2V
Timer On (Circuit Breaker, Sourcing), V
TMR
= 2V
Timer Off (Cooling Cycle, Sinking), V
TMR
= 2V
LTC4251/LTC4251-1
CONDITIONS
(Before Gate Ramp-Up)
LTC4251/LTC4251-2
LTC4251-1
LTC4251/LTC4251-2
LTC4251-1
LTC4251/LTC4251-2
LTC4251-1
LTC4251
LTC4251-1
LTC4251
LTC4251-1
LTC4251
LTC4251-1
UV/OV = 4V, V
SENSE
= 50mV
UV/OV = 4V
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ELECTRICAL CHARACTERISTICS
MIN
3.075
2.300
2.775
2.050
TYP
0.5
3.225
2.420
2.925
2.160
0.30
0.26
MAX
3.375
2.540
3.075
2.270
UNITS
V
V
V
V
V
V
V
5.85
5.86
5.25
5.61
6.15
6.17
5.55
5.91
0.60
0.26
6.45
6.48
5.85
6.21
V
V
V
V
V
V
µA
–30
–15
±0.1
4
1
5.8
28
230
5.8
0.7
1
±1
µA
V
V
µA
mA
µA
µA
µs
µs
t
PLLUG
t
PHLOG
UV Low to GATE Low
OV High to GATE Low
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.
Note 3:
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
TYPICAL PERFORMANCE CHARACTERISTICS
2000
1800
1600
1400
I
IN
(µA)
I
IN
(mA)
1200
1000
800
600
400
200
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G01
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
r
Z
vs Temperature
I
IN
= 2mA
I
IN
vs Temperature
V
IN
= (V
Z
– 0.3V)
1000
I
IN
vs V
IN
T
A
= –40°C
10
9
8
T
A
= 25°C
7
r
Z
( )
6
5
100
10
T
A
= 85°C
T
A
= 125°C
1
4
3
0.1
0
2
4
6
8 10 12 14 16 18 20 22
V
IN
(V)
425112 G02
2
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G03
425112fd
For more information
www.linear.com/4251
3
LTC4251/LTC4251-1/
LTC4251-2
TYPICAL PERFORMANCE CHARACTERISTICS
V
Z
vs Temperature
14.5
I
IN
= 2mA
12.0
11.5
14.0
11.0
10.5
V
LKO
(V)
V
LKH
10.0
9.5
9.0
8.5
12.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G04
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
Undervoltage Lockout Hysteresis
V
LKH
vs Temperature
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
Undervoltage Lockout V
LKO
vs
Temperature
13.5
V
Z
(V)
13.0
12.5
8.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G05
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G06
Circuit Breaker Current Limit
Voltage V
CB
vs Temperature
60
58
56
54
V
CB
(mV)
V
ACL
(V)
52
50
48
46
44
42
40
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G07
Analog Current Limit Voltage V
ACL
vs Temperature
120
115
110
V
FCL
(mV)
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G08
Fast Current Limit Voltage V
FCL
vs Temperature
300
275
250
225
200
175
150
–55 –35 –15
105
100
95
90
85
80
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G09
I
GATE
(Source) vs Temperature
70
UV/0V = 4V
TIMER = 0V
65 V
SENSE
= V
EE
V
GATE
= 0V
60
I
GATE
(mA)
I
GATE
(µA)
55
50
45
40
–55 –35 –15
30
25
20
I
GATE
(ACL, Sink) vs Temperature
UV/0V = 4V
TIMER = 0V
V
SENSE
– V
EE
= 0.15V
V
GATE
= 3V
I
GATE
(mA)
400
350
300
250
200
150
100
5
0
–55 –35 –15
50
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G11
I
GATE
(FCL, Sink) vs Temperature
UV/0V = 4V
TIMER = 0V
V
SENSE
– V
EE
= 0.3V
V
GATE
= 1V
15
10
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G10
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G12
425112fd
4
For more information
www.linear.com/4251
LTC4251/LTC4251-1/
LTC4251-2
TYPICAL PERFORMANCE CHARACTERISTICS
V
GATE
vs Temperature
14.5
14.0
13.5
13.0
12.5
12.0
11.5
11.0
10.5
10.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G13
UV/OV = 4V refers to UV = 4V for the LTC4251-2.
V
GATEL
vs Temperature
0.8
0.7
0.6
V
GATEL
(V)
0.5
0.4
0.3
0.2
0.1
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G14
UV Threshold vs Temperature
3.375
LTC4251/LTC4251-2
3.275
UV THRESHOLD (V)
3.175
3.075
2.975
2.875
2.775
–55 –35 –15
V
UVH
UV/0V = 4V
V
TMR
= 0V
V
SENSE
= V
EE
UV/0V = 4V,
V
TMR
= 0V,
GATE THRESHOLD
BEFORE RAMP-UP
V
GATE
(V)
V
UVL
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G15
UV Threshold vs Temperature
2.55
2.50
2.45
UV THRESHOLD (V)
2.40
2.35
2.30
2.25
2.20
2.15
2.10
2.05
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G16
OV Threshold vs Temperature
6.45
6.51
LTC4251
6.25
6.41
V
OVH
OV THRESHOLD (V)
6.31
6.21
6.11
6.01
5.91
5.81
5.71
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G17
OV Threshold vs Temperature
LTC4251-1
LTC4251-1
V
UVHI
OV THRESHOLD (V)
6.05
5.85
5.65
5.45
V
OVHI
V
UVLO
V
OVL
V
OVLO
5.25
–55 –35 –15
5.61
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G18
I
SENSE
vs Temperature
–10
–12
–14
–16
–I
SENSE
(mA)
I
SENSE
(µA)
–18
–20
–22
–24
–26
–28
–30
–55 –35 –15
UV/0V = 4V
TIMER = 0V
GATE = HIGH
V
SENSE
– V
EE
= 50mV
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G19
I
SENSE
vs (V
SENSE
– V
EE
)
0.01
5.0
4.5
0.1
TIMER THRESHOLD (V)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
TIMER Threshold vs Temperature
V
TMRH
1.0
10
UV/0V = 4V
TIMER = 0V
GATE = HIGH
T
A
= 25°C
1.5
2.0
100
V
TMRL
1000
–1.5 –1.0 –0.5
0
0.5 1.0
(V
SENSE
– V
EE
) (V)
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
425112 G21
425112 G20
425112fd
For more information
www.linear.com/4251
5
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