LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
Negative Voltage
Hot Swap Controllers
FEATURES
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DESCRIPTIO
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 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
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 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.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
APPLICATIO S
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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 APPLICATIO
GND
– 48V/2.5A Hot Swap Controller
R
IN
3× 1.8k IN SERIES
1/4W EACH
C
IN
1µF
R1
402k
1%
V
IN
LTC4252-1
OV
UV
R2
32.4k
1%
C1
10nF
TIMER
C
T
0.33µF
SS
C
SS
68nF
V
EE
PWRGD
DRAIN
GATE
SENSE
R
C
10Ω
C
C
18nF
R
S
0.02Ω
PWRGD
10V/DIV
4252-1/2 TA01
+
C
L
100µF
LOAD
EN
GATE
5V/DIV
GND
(SHORT PIN)
R3
5.1k
*
R
D
1M
V
OUT
SENSE
2.5A/DIV
Q1
IRF530S
V
OUT
20V/DIV
–48V
* M0C207
U
Start-Up Behavior
1ms/DIV
4252-1/2 TA01a
U
U
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1
LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
ABSOLUTE
AXI U RATI GS
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
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
IN
SS
SENSE
V
EE
1
2
3
4
8
7
6
5
TIMER
UV/OV
DRAIN
GATE
V
IN
PWRGD
SS
SENSE
V
EE
1
2
3
4
5
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
ORDER PART NUMBER
LTC4252-1CMS8
LTC4252-2CMS8
LTC4252-1IMS8
LTC4252-2IMS8
MS8 PART MARKING
LTWM
LTWP
LTRQ
LTRR
Order Options
Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
2
U
U
W
W W
U
W
All Voltages Referred to V
EE
(Note 1)
Operating Temperature Range
LTC4252-1C/LTC4252-2C
LTC4252A-1C/LTC4252A-2C ................... 0°C to 70°C
LTC4252-1I/LTC4252-2I
LTC4252A-1I/LTC4252A-2I ............... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
10
9
8
7
6
TIMER
UV
OV
DRAIN
GATE
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
ORDER PART NUMBER
LTC4252-1CMS
LTC4252-2CMS
LTC4252A-1CMS
LTC4252A-2CMS
LTC4252-1IMS
LTC4252-2IMS
LTC4252A-1IMS
LTC4252A-2IMS
MS PART MARKING
LTWN
LTWQ
LTAFX
LTAGE
LTRS
LTRT
LTAFY
LTAGF
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LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
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 LTC4252A Only)
UV = OV = 4V, V
SENSE
= 50mV
UV = OV = 4V
Low-to-High Transition
(
●
for LTC4252A 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)
●
●
●
●
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
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
●
●
●
●
●
●
●
LTC4252-1/-2
MIN TYP MAX
11.5
13
5
0.8
9.2
1
40
80
50
100
60
120
2
11.5
14.5
LTC4252A-1/-2
MIN TYP MAX
11.5
13
5
0.9
9
0.5
45
50
55
2
10
14.5
UNITS
V
Ω
mA
V
V
mV
mV
1.05
150
200
2.2
100
22
28
10
0.05
40
58
17
190
10
12
2.8
0.5
3.075 3.225 3.375
2.775 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
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3
LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
The
●
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 LTC4252A)
I
DRN
= 50µA
I
PG
= 1.6mA (MS Only)
I
PG
= 5mA (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
LTC4252-1/-2
MIN TYP MAX
5.8
LTC4252A-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
V
PWRGD
= 0V (Sourcing) (MS Only)
●
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.
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4
LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
TYPICAL PERFOR A CE CHARACTERISTICS
V
Z
vs Temperature
14.5
I
IN
= 2mA
14.0
6
5
4
I
IN
(µA)
13.5
V
Z
(V)
r
Z
(Ω)
13.0
12.5
12.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252-1/2 G04
I
IN
vs V
IN
1000
T
A
= –40°C
100
T
A
= 25°C
V
LKO
(V)
10
T
A
= 85°C
T
A
= 125°C
10.0
9.5
V
LKH
(V)
I
IN
(mA)
1
0.1
0
2
4
6
8 10 12 14 16 18 20 22
V
IN
(V)
4252-1/2
G02
Circuit Breaker Current Limit
Voltage V
CB
vs Temperature
60
58
56
54
V
ACL
(mV)
50
48
46
44
42
40
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252-1/2 G07
100
95
90
85
80
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252-1/2 G08
V
FCL
(mV)
V
CB
(mV)
52
U W
r
Z
vs Temperature
10
9
8
7
I
IN
= 2mA
2000
1800
1600
1400
1200
1000
800
600
400
200
I
IN
vs Temperature
V
IN
= (V
Z
– 0.3V)
3
2
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252-1/2 G03
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252-1/2 G01
Undervoltage Lockout V
LKO
vs Temperature
12.0
11.5
11.0
10.5
Undervoltage Lockout Hysteresis
V
LKH
vs Temperature
1.5
1.3
1.1
0.9
9.0
0.7
8.5
8.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252-1/2 G05
0.5
–55
–35
–15
5
25 45
65 95 105
125
TEMPERATURE (°C)
4252-1/2 G06
Analog Current Limit Voltage
V
ACL
vs Temperature
120
115
110
105
250
225
200
175
300
275
Fast Current Limit Voltage V
FCL
vs Temperature
150
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
4252-1/2 G09
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5
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