power paths to be safely inserted and removed from a
live backplane or powered connector. Using N-channel
pass transistors, supply voltages ranging from 4.5V to
44V are ramped up at an adjustable rate.
Three selectable ratios of current limit to circuit breaker
threshold accommodate noisy loads and momentary high
peak currents without interruption, while a dual-rate fault
timer protects the MOSFET from extended output over-
current events.
FAULT
outputs indicate the circuit breaker
status. The LTC4226-1 remains off after a fault while the
LTC4226-2 automatically retries after a 0.5s delay.
The LTC4226 can also be configured as a bidirectional cur-
rent limiter/circuit breaker. For high current applications,
two channels may be configured as parallel power paths.
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.
n
n
n
n
n
n
Allows Safe Board Insertion into Live Backplane
Selectable Current Limit and Dual-Rate Timer
Accommodate Load Surges
Fast Response Limits Peak Fault Current
Wide Operating Voltage Range: 4.5V to 44V
Optional Auto-Retry or Latchoff after
Overcurrent Fault
High Side Drive for External N-Channel MOSFET
Allows Parallel Power Paths for High Current
Applications
Available in 16-Pin QFN (3mm
×
3mm) and MSOP
Packages
applicaTions
n
n
n
n
n
Apple FireWire/IEEE 1394
Disk Drives
Rugged 12V, 24V Applications
Hot Board/Connector Insertion
Uni/Bidirectional Current Limiter/Circuit Breaker
Typical applicaTion
2 Port FireWire Application
SS3P5
7V TO 33V
V
CC1
ON1
CURRENT
LIMIT
SELECT
FAULT1
CLS
FAULT2
ON2
V
CC2
SENSE2 GATE2
FTMR2
OUT2
PORT 2
1394
1394
SOCKET PLUG
LTC4226-2
GND
220nF
I
OUT
1A/DIV
INRUSH
CURRENT
SENSE1 GATE1
OUT1
FTMR1
220nF
V
OUT
10V/DIV
30m
FDMS86500DC
PORT 1
1394
1394
SOCKET PLUG
Inrush after Load Connection
V
CC
10V/DIV
CABLE INSERTION
SMCJ33A*
30m
FDMS86500DC
4226 TA01a
*36.7V TO 40.6V BV
V
CC
= 12V
C
LOAD
= 1mF
1ms/DIV
4226 TA01b
4226f
1
LTC4226
absoluTe MaxiMuM raTings
(Notes 1, 2)
V
CCn
........................................................... –0.3V to 55V
SENSEn, ONn,
FAULTn,
CLS ....................... –0.3V to 55V
GATEn (Note 3) .......................................... –0.3V to 68V
OUTn (Note 3) ............................................ –0.3V to 55V
GATEn – OUTn (Note 3) ............................. –0.3V to 18V
FTMRn ......................................................... –0.3V to 4V
Operating Ambient Temperature Range
LTC4226C ................................................ 0°C to 70°C
LTC4226I .............................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
MSOP Lead Temperature (Soldering, 10 sec)........ 300°C
pin conFiguraTion
TOP VIEW
FAULT1
FAULT2
ON1
ON2
16 15 14 13
V
CC1
SENSE1
GATE1
OUT1
1
2
3
4
5
FTMR1
6
GND
7
CLS
8
FTMR2
17
12 V
CC2
11 SENSE2
10 GATE2
9
OUT2
TOP VIEW
FAULT1
ON1
V
CC1
SENSE1
GATE1
OUT1
FTMR1
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
FAULT2
ON2
V
CC2
SENSE2
GATE2
OUT2
FTMR2
CLS
UD PACKAGE
16-LEAD (3mm
×
3mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 68°C/W
EXPOSED PAD (PIN 17), PCB GND CONNECTION OPTIONAL
MS PACKAGE
16-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 120°C/W
orDer inForMaTion
LEAD FREE FINISH
LTC4226CUD-1#PBF
LTC4226CUD-2#PBF
LTC4226IUD-1#PBF
LTC4226IUD-2#PBF
LTC4226CMS-1#PBF
LTC4226CMS-2#PBF
LTC4226IMS-1#PBF
LTC4226IMS-2#PBF
TAPE AND REEL
LTC4226CUD-1#TRPBF
LTC4226CUD-2#TRPBF
LTC4226IUD-1#TRPBF
LTC4226IUD-2#TRPBF
LTC4226CMS-1#TRPBF
LTC4226CMS-2#TRPBF
LTC4226IMS-1#TRPBF
LTC4226IMS-2#TRPBF
PART MARKING*
LFRC
LFRD
LFRC
LFRD
42261
42262
42261
42262
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-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
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 nonstandard 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/
4226f
2
LTC4226
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 12V.
SYMBOL
Supplies
V
CCn
I
CCn
V
CCn(UVL)
Input Supply Range
Input Supply Current
Input Supply Undervoltage Lockout
V
CC
= 12V
V
CC
Rising
l
l
l
elecTrical characTerisTics
PARAMETER
CONDITIONS
MIN
4.5
TYP
MAX
44
UNITS
V
mA
V
mV
0.7
3
3.7
200
2
4.5
∆V
CCn(HYST)
Input Supply Undervoltage Lockout Hysteresis
Circuit Breaker and Current Limit
V
CB
V
LIMIT
Circuit Breaker Threshold
Channel-to-Channel V
CB
Mismatch
Current Limit Voltage
(V
CC
– SENSE), CLS = 0V
(V
CC
– SENSE), CLS = Open
(V
CC
– SENSE), CLS = 3V
(V
CC
– SENSE = 0V)
I
GATE
= 0µA, –1µA; V
CC
> 6V
I
GATE
= 0µA, –1µA; V
CC
< 6V
GATE = OUT = 1V
GATE = 12V, OUT = 0V, ON = 0V
GATE = OUT = V
CC
= 12V, ON = 0V or
FAULT
= 0V
GATE = 5V, OUT = 0V, ON = 3V, Severe Fault
V
ON
Rising
V
ON
= 1.2V
V
FTMR
= 0V, Circuit Breaker Fault
V
FTMR
= 0V, Current Limit Engaged, CLS = 0V
V
FTMR
= 0V, Current Limit Engaged, CLS = Open
V
FTMR
= 0V, Current Limit Engaged, CLS = 3V
V
FTMR
= 1V, Default
V
FTMR
= 1V, Reset
(V
CC
– SENSE)
l
l
l
l
l
l
l
45
70
93
139
50
86
115
173
40
55
±6
103
136
205
±6
200
16
16
–13
5
300
1000
1.3
±1
–2.6
–26
–46
–104
2.6
130
1.3
0.2
0.4
10
0.8
–20
5
mV
%
mV
mV
mV
%
µA
V
V
µA
mA
µA
mA
V
mV
µA
µA
µA
µA
µA
µA
µA
V
V
V
mA
V
µA
V
Channel-to-Channel V
LIMIT
Mismatch
I
SENSE
Gate Drive
∆V
GATE
I
GATE(UP)
I
GATE(DN)
External N-Channel Gate Drive (GATE – OUT)
Gate Pull-Up Current
Gate Pull-Down Current
Sense Pin Input Current
l
l
l
l
l
l
10
8
–5
1
50
100
1.17
12
12
–9
3
150
200
1.24
50
0
Comparator Inputs
V
ON
I
ON
Fault Timer
I
FTMR(CB)
I
FTMR(CL)
I
FTMR(DEF)
I
FTMR(RST)
V
FTMR(H)
V
FTMR(L)
Fault I/O
V
(OL)
I
(OL)
V
FAULT
I
(OH)
V
(OH)
FAULT
Pin Low Output Voltage
FAULT
Pin Low Output Pull-Down Current
FAULT
Pin Input Threshold Voltage
FAULT
Pin Pull-Up Current
FAULT
Pin High Output Voltage
Circuit Breaker Fault, I
FAULT
= 2mA
Circuit Breaker Fault, V
FAULT
= 5V, V
CC
= 12V
No Internal Fault, External Input
No Internal Fault, V
FAULT
= 2V
No Internal Fault, I
FAULT
= 0µA, V
CC
= 12V
l
l
l
l
l
ON Pin Threshold Voltage
ON Pin Input Current
FTMR Pin Pull-Up Current (Circuit Breaker)
FTMR Pin Pull-Up Current (Current Limit)
l
∆V
ON(HYST)
ON Pin Hysteresis Voltage
l
l
l
l
l
l
l
l
l
–1.4
–14
–25
–56
1.4
70
1.17
–2
–20
–36
–80
2
100
1.23
0.1
0.2
FTMR Pin Pull-Down Current (Default)
FTMR Pin Pull-Down Current (Reset)
FTMR Pin Threshold Voltage (Trip)
FTMR Pin Threshold Voltage (Reset)
2
0.3
–5
2
5
0.5
–10
3.8
4226f
3
LTC4226
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 12V.
SYMBOL
V
CLS(L)
V
CLS(H)
V
CLS(Z)
I
CLS(Z)
I
CLS(L)
I
CLS(H)
Timing Delay
t
OFF(SENSE)
t
OFF(FAULT)
t
OFF(FMTR)
t
OFF(ON)
t
OFF(UVLO)
t
ON(ON)
t
ON(UVL)
t
D(COOL)
Severe Overcurrent Fault to GATE Low
FAULT
Input Low to GATE Low
FTMR High to GATE Low
ON Low to GATE Low
V
CC
Enters Undervoltage to GATE Low
ON High to GATE High
Channel-to-Channel t
ON(ON)
Mismatch
V
CC
Exits Undervoltage to GATE High
Channel-to-Channel t
ON(UVL)
Mismatch
Auto-Retry Delay
LTC4226-2 Only
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 pins are positive, all voltages are referenced to
GND unless otherwise specified.
ON High
C
GATE
= 1nF, (V
CC
– SENSE = 4V)
C
GATE
= 1nF
C
GATE
= 1nF
C
GATE
= 1nF
C
GATE
= 1nF
V
CC
Above Undervoltage
l
l
l
l
l
l
l
l
l
l
elecTrical characTerisTics
PARAMETER
CLS Pin Low Threshold Voltage
CLS Pin High Threshold Voltage
CLS Pin Voltage in Open State
Allowable CLS Pin Leakage in Open State
CLS Pin Low Input Current
CLS Pin High Input Current
Three-State Input
CONDITIONS
l
l
MIN
TYP
MAX
0.4
UNITS
V
V
V
2
1.38
±2
–2
2
–4
4
0.1
3
3
6
7
25
25
5
25
0.25
10
50
0.5
–8
8
1
30
30
60
60
20
±10
100
±10
1
l
l
l
µA
µA
µA
µs
µs
µs
µs
µs
ms
%
ms
%
s
Note 3:
Limits on maximum rating is defined as whichever limit occurs
first. Internal clamps limit the GATE pin to a minimum of 12V above OUT, a
diode voltage drop below OUT, or a diode voltage drop below GND. Driving
the GATE to OUT pin voltage beyond the clamp may damage the device.
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