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 cur-
rent under worst-case catastrophic fault conditions. The
LTC4253B latches off after a circuit fault.
Adjustable undervoltage and overvoltage detectors dis-
connect the load whenever the input supply exceeds the
desired operating range. The LTC4253B’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 can be 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.
Three power good outputs are sequenced by an adjustable
timer and two ENABLE inputs to enable external power
modules at start-up or disable them if the circuit breaker
trips. The LTC4253B improves the ruggedness of the
LTC4253 shunt regulator.
n
n
n
n
n
n
n
n
Allows Safe Board Insertion and Removal from a
Live –48V Backplane
Floating Topology Permits Very High Voltage
Operation
Adjustable Analog Current Limit with Breaker Timer
Ideal for Two Battery Feeds
Fast Response Time Limits Peak Fault Current
Three Sequenced Power Good Outputs
Improved Ruggedness Shunt Regulator
Adjustable Soft-Start Current Limit
Adjustable Timer with Drain Voltage Accelerated
Response
Latchoff After Fault
Available in a 16-Pin SSOP Package
applicaTions
n
n
n
n
n
–48V Distributed Power Systems
Negative Power Supply Control
Central Office Switching
High Availability Servers
Disk Arrays
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
– 48V/2.5A Hot Swap Controller
– 48V RTN
1µF
– 48V RTN
402k
1%
10nF
EN2 EN3 V
IN
D
IN††
LTC4253B
DDZ13B*
RESET
UV
OV
32.4k
1%
68nF
0.1µF
– 48V A
B3100*
0.33µF
SS
SQTIMER
TIMER
PWRGD1
PWRGD2
PWRGD3
DRAIN
GATE
SENSE
10
18nF
0.02
1M
IRF530S
*DIODES, INC.
†
MOC207
††
RECOMMENDED FOR HARSH ENVIRONMENTS.
V
OUT
50V
1ms/DIV
4253b TA01b
2.5k
15k(1/4W)/6
5.6k
V
IN
5.6k
100µF
5.6k
+
Start-Up Behavior
LOAD1
LOAD2
EN
EN
EN
LOAD3
GATE
10V
†
†
†
SS
1V
4253b TA01
SENSE
50mV
V
EE
– 48V B
B3100*
4253bf
1
LTC4253B
absoluTe MaxiMuM raTings
(Note 1), All voltages referred to V
EE
pin conFiguraTion
TOP VIEW
EN2
PWRGD2
PWRGD1
V
IN
RESET
SS
SENSE
V
EE
1
2
3
4
5
6
7
8
16 PWRGD3
15 EN3
14 SQTIMER
13 TIMER
12 UV
11 OV
10 DRAIN
9
GATE
Current into V
IN
(100µs Pulse) .............................100mA
Current into DRAIN (100µs Pulse) .........................20mA
V
IN
, DRAIN Minimum Voltage ................................–0.3V
Input/Output (Except SENSE
and DRAIN) Voltage ................................... –0.3V to 16V
SENSE Voltage ........................................... –0.6V to 16V
Current Out of SENSE (20µs Pulse) .................. –200mA
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range
LTC4253BC .............................................. 0°C to 70°C
LTC4253BI ...........................................–40°C to 85°C
Storage Temperature Range .............. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 110°C/W
orDer inForMaTion
LEAD FREE FINISH
LTC4253BCGN#PBF
LTC4253BIGN#PBF
TAPE AND REEL
LTC4253BCGN#TRPBF
LTC4253BIGN#TRPBF
PART MARKING*
4253B
4253B
PACKAGE DESCRIPTION
16-Lead Plastic SSOP
16-Lead Plastic SSOP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
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/
4253bf
2
LTC4253B
elecTrical characTerisTics
SYMBOL
V
Z
R
Z
I
IN
V
LKO
V
LKH
V
IH
V
IL
V
HYST
I
RESET
I
EN
V
CB
V
ACL
V
FCL
V
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
TTL Input High Voltage
TTL Input Low Voltage
TTL Input Buffer Hysteresis
RESET Input Current
EN2, EN3 Input Current
Circuit Breaker Current Limit Voltage
Analog Current Limit Voltage
Fast Current Limit Voltage
SS Voltage
SS Pin Current
V
EE
≤ V
RESET
≤ V
IN
V
EN
= 4V
V
EN
= 0V
V
CB
= (V
SENSE
– V
EE
)
V
ACL
= (V
SENSE
– V
EE
), SS = Open or 2.2V
V
FCL
= (V
SENSE
– V
EE
)
After End of SS Timing Cycle
UV = OV = 4V, V
SENSE
= V
EE,
V
SS
= 0V (Sourcing)
UV = OV = 0V, V
SENSE
= V
EE,
V
SS
= 1V (Sinking)
R
SS
V
OS
SS Output Impedance
Analog Current Limit Offset Voltage
●
●
●
●
●
●
●
●
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
)
●
●
●
●
●
●
MIN
11.5
TYP
13
5
0.8
9.2
MAX
14.5
2
11.5
1.5
0.8
UNITS
V
Ω
mA
V
V
V
V
mV
µA
µA
µA
mV
mV
mV
V
µA
mA
kΩ
mV
V/V
0.5
2
1
600
±0.1
60
40
80
150
2
12
120
±0.1
50
100
200
2.2
22
28
100
10
0.05
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)
●
±10
180
±10
60
120
300
2.4
32
V
ACL
+ V
OS
Ratio (V
ACL
+ V
OS
) to SS Voltage
V
SS
I
GATE
GATE Pin Output Current
30
50
17
190
70
µA
mA
mA
V
GATE
V
GATEL
V
GATEH
V
UVHI
V
UVLO
V
UVHST
V
OVHI
V
OVLO
V
OVHST
I
SENSE
I
INP
V
TMRH
External MOSFET Gate Drive
Gate Low Threshold
Gate High Threshold
UV Pin Threshold HIGH
UV Pin Threshold LOW
UV Pin Hysteresis
OV Pin Threshold HIGH
OV Pin Threshold LOW
OV Pin Hysteresis
SENSE Pin Input Current
UV, OV Pin Input Current
TIMER Pin Voltage High Threshold
V
GATE
– V
EE,
I
IN
= 2mA
Before Gate Ramp Up
V
GATEH
= V
IN
– V
GATE
, for
PWRGD1,
PWRGD2, PWRGD3
Status
UV Low to High
UV High to Low
OV Low to High
OV High to Low
UV = 0V = 4V, V
SENSE
= 50mV (Sourcing)
UV = OV = 4V
●
10
12
0.5
2.8
V
Z
V
V
V
●
●
3.075
2.775
230
5.85
5.55
230
3.225
2.925
300
6.15
5.85
300
15
± 0.1
3.375
3.075
350
6.45
6.15
350
30
±1
4.5
V
V
mV
V
V
mV
µA
µA
V
4253bf
●
●
●
●
●
3.5
4
3
LTC4253B
elecTrical characTerisTics
SYMBOL
V
TMRL
I
TMR
PARAMETER
TIMER Pin Voltage Low Threshold
TIMER Pin Current
Timer On (Initial Cycle/Latchoff,
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, Sinking),
V
TMR
= 2V
∆I
TMRACC
∆I
DRN
V
SQTMRH
V
SQTMRL
I
SQTMR
I
TMR
at I
DRN
= 50µA – I
TMR
at I
DRN
= 0µA
50µA
SQTIMER Pin Voltage High Threshold
SQTIMER Pin Voltage Low Threshold
SQTIMER Pin Current
SQTIMER On (Power Good
Sequence, Sourcing), V
SQTMR
= 2V
SQTIMER Off (Power Good
Sequence, Sinking), V
SQTMR
= 2V
V
DRNL
I
DRNL
V
DRNCL
V
PGL
I
PGH
t
SQ
t
SS
t
PLLUG
t
PHLOG
DRAIN Pin Voltage Low Threshold
DRAIN Leakage Current
DRAIN Pin Clamp Voltage
PWRGD1, PWRGD2, PWRGD3
Output Low Voltage
PWRGD1, PWRGD2, PWRGD3
Output High Current
SQTIMER Default Ramp Period
SS Default Ramp Period
UV Low to GATE Low
OV High to GATE Low
For
PWRGD1, PWRGD2, PWRGD3
Status
V
DRAIN
= 5V
V
DRAIN
= 4V
I
DRN
= 50µA
I
PG
= 1.6mA
I
PG
= 5mA
V
PG
= 0V (Sourcing)
SQTIMER Pin Floating,
V
SQTMR
Ramps from 0.5V to 3.5V
SS Pin Floating, V
SS
Ramps from 0.2V to 2V
●
●
●
●
●
●
●
●
●
●
●
●
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
CONDITIONS
●
●
MIN
0.8
3
TYP
1
5
28
MAX
1.2
7
UNITS
V
µA
mA
120
200
600
280
µA
µA
3
7
3.5
3
5
8
4
0.33
5
28
7
9
4.5
7
µA
µA/µA
V
V
µA
mA
Timer On (Circuit Breaker with
I
DRN
= 50µA)
2
2.39
± 0.1
3
±1
8.5
0.4
1.2
70
V
µA
µA
V
V
V
µA
µs
µs
6
7
0.25
30
50
250
250
0.4
0.4
5
5
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
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