LT1641-1/LT1641-2
Positive High Voltage
Hot Swap Controllers
FEATURES
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DESCRIPTIO
Allows Safe Board Insertion and Removal from a
Live Backplane
Controls Supply Voltage from 9V to 80V
Programmable Analog Foldback Current Limiting
High Side Drive for an External N-Channel
Latched Operation Mode (LT1641-1)
Automatic Retry (LT1641-2)
User Programmable Supply Voltage Power-Up Rate
Undervoltage Lockout
Overvoltage Protection
Both are available in 8-Lead SO Package
The LT
®
1641-1/LT1641-2 are 8-pin Hot Swap
TM
control-
lers that allow a board to be safely inserted and removed
from a live backplane. Using an external N-channel pass
transistor, the board supply voltage can be ramped up at
a programmable rate. A high side switch driver controls an
N-channel gate for supply voltages ranging from 9V to
80V.
The chips feature a programmable analog foldback cur-
rent limit circuit. If the chips remain in current limit for
more than a programmable time, the N-channel pass
transistor is either latched off (LT1641-1) or is set to
automatically restart after a time-out delay (LT1641-2).
The PWRGD output indicates when the output voltage,
sensed by the FB pin, is within tolerance. The ON pin
provides programmable undervoltage lockout.
The LT1641-1/LT1641-2 are available in the 8-lead SO
package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
APPLICATIO S
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Hot Board Insertion
Electronic Circuit Breaker
Industrial High Side Switch/Circuit Breaker
24V/48V Industrial/Alarm Systems
TYPICAL APPLICATIO
V
IN
24V
24V Input Voltage Application
R
S
0.01Ω
Q1
IRF530
V
OUT
SHORT
PIN
R1
49.9k
1%
R5
10Ω
5%
D1
CMPZ
5248B
C1
R6, 10nF
1k, 5%
R7
24k
5%
FB
LT1641-1/LT1641-2
R2
3.4k
1%
TIMER
C2
0.68µF
*DIODES, INC.
1641-1 TA01
R3
59k
1%
*SMAT70A
V
CC
ON
SENSE
GATE
R4
3.57k
1%
PWRGD
GND
GND
U
C
L
PWRGD
164112fc
U
U
1
LT1641-1/LT1641-2
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
ON 1
FB 2
PWRGD 3
GND 4
8
7
6
5
V
CC
SENSE
GATE
TIMER
Supply Voltage (V
CC
) ...............................– 0.3V to 100V
Input Voltage (SENSE) .............................– 0.3V to 100V
Input Voltage (TIMER) ...............................– 0.3V to 44V
Input Voltage (FB, ON) ...............................– 0.3V to 60V
Output Voltage (PWRGD) ........................– 0.3V to 100V
Output Voltage (GATE) ............................– 0.3V to 100V
Operating Temperature Range
LT1641-1C, LT1641-2C ........................... 0°C to 70°C
LT1641-1I, LT1641-2I ........................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 110°C/W
ORDER PART NUMBER
LT1641-1CS8
LT1641-1IS8
LT1641-2CS8
LT1641-2IS8
S8 PART MARKING
16411
16411I
16412
16412I
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.
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
cc
= 24V
SYMBOL
V
CC
I
CC
V
LKO
V
FBH
V
FBL
V
FBHST
I
INFB
∆V
FB
V
SENSETRIP
I
GATEUP
I
GATEDN
∆V
GATE
I
TIMERUP
I
TIMERON
V
ONH
V
ONL
V
ONHYST
I
INON
V
OL
I
OH
PARAMETER
V
CC
Operating Range
V
CC
Supply Current
V
CC
Undervoltage Lockout
FB Pin High Voltage Threshold
FB Pin Low Voltage Threshold
FB Pin Hysteresis Voltage
FB Pin Input Current
FB Pin Threshold Line Regulation
SENSE Pin Trip Voltage (V
CC
– V
SENSE
)
GATE Pin Pull-Up Current
GATE Pin Pull-Down Current
External N-Channel Gate Drive
TIMER Pin Pull-Up Current
TIMER Pin Pull-Down Current
ON Pin High Threshold
ON Pin Low Threshold
ON Pin Hysteresis
ON Pin Input Current
PWRGD Output Low Voltage
PWRGD Pin Leakage Current
V
ON
= GND
I
O
= 2mA
I
O
= 4mA
V
PWRGD
= 80V
●
●
●
DC ELECTRICAL CHARACTERISTICS
CONDITIONS
●
MIN
9
●
●
TYP
2
MAX
80
5.5
8.8
1.345
1.245
–1
UNITS
V
mA
V
V
V
mV
µA
mV/V
mV
mV
µA
mA
V
V
µA
µA
V
V
mV
µA
V
V
µA
164112fc
ON = 3V
FB Low to High Transition
FB High to Low Transition
V
FB
= GND
9V
≤
V
CC
≤
80V
V
FB
= 0V
V
FB
= 1V
Charge Pump On, V
GATE
= 7V
Any Fault Condition, V
GATE
= 2V
V
GATE
– V
CC
, V
CC
= 10.8V to 20V
V
CC
= 20V to 80V
V
TIMER
= 0V
V
TIMER
= 1V
ON Low to High Transition
ON High to Low Transition
7.5
1.280
1.221
8.3
1.313
1.233
80
●
●
●
●
●
●
●
●
●
●
●
●
●
0.05
8
39
–5
35
4.5
10
– 24
1.5
1.280
1.221
– 80
3
1.313
1.233
80
–1
0.4
2.5
10
12
47
– 10
70
17
55
– 20
100
18
18
– 132
5
1.345
1.245
2
U
W
U
U
W W
W
LT1641-1/LT1641-2
AC ELECTRICAL CHARACTERISTICS
SYMBOL
t
PHLON
t
PLHON
t
PHLFB
t
PLHFB
t
PHLSENSE
PARAMETER
ON Low to GATE Low
ON High to GATE High
FB Low to PWRGD Low
FB High to PWRGD High
(V
CC
– SENSE) High to GATE Low
CONDITIONS
Figures 1, 2
Figures 1, 2
Figures 1, 3
Figures 1, 3
Figures 1, 4
T
A
= 25°C, V
CC
= 24V
MIN
TYP
6
1.7
3.2
1.5
0.5
1
2
MAX
UNITS
µs
µs
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 ground unless otherwise
specified.
TYPICAL PERFOR A CE CHARACTERISTICS
I
CC
vs V
CC
3.5
3.0
2.5
I
CC
(mA)
2.0
1.5
1.0
0.5
0
0
20
40
60
V
CC
(V)
80
100
1641-1 G01
85°C
25°C
–45°C
I
CC
(mA)
48V
2.5
24V
2.0
1.5
1.0
0.5
0
–50
FB PIN LOW VOLTAGE THRESHOLD (V)
FB Pin High Voltage Threshold vs
Temperature
1.335
0.100
V
CC
= 48V
FB PIN HYSTERESIS (V)
FB PIN HIGH VOLTAGE THRESHOLD (V)
1.330
1.325
1.320
1.315
1.310
1.305
1.300
1.295
1.290
1.285
1.280
–50
0.080
0.075
0.070
0.065
0.060
0.055
0.050
0.045
0.040
–50
I
GATE
PULL UP (µA)
–25
0
25
50
TEMPERATURE (°C)
U W
75
1641-1 G04
I
CC
vs Temperature
3.0
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
1.205
FB Pin Low Voltage Threshold vs
Temperature
V
CC
= 48V
–25
0
25
50
TEMPERATURE (°C)
75
100
1.200
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1641-1 G02
1641-1 G03
FB Pin Hysteresis vs Temperature
–5
V
CC
= 48V
–6
–7
–8
–9
–10
–11
–12
–25
0
25
50
TEMPERATURE (°C)
75
100
0.095
0.090
0.085
I
GATE
Pull Up vs Temperature
V
CC
= 48V
100
–13
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1641-1 G05
1641-1 G06
164112fc
3
LT1641-1/LT1641-2
TYPICAL PERFOR A CE CHARACTERISTICS
Gate Drive vs Temperature
16
15
GATE DRIVE (V
GATE
– V
CC
) (V)
14
13
12
11
10
9
8
7
6
–50
–25
V
CC
= 10.8V
V
CC
= 48V
16
TIMER PIN PULL UP CURRENT (µA)
GATE DRIVE (V
GATE
– V
CC
) (V)
0
25
50
TEMPERATURE (°C)
TIMER Pin Pull Up Current vs V
CC
16
ON PIN HIGH VOLTAGE THRESHOLD (V)
TIMER PIN PULL UP CURRENT (µA)
1.330
1.325
1.320
1.315
1.310
1.305
1.300
1.295
1.290
1.285
–50
ON PIN LOW VOLTAGE THRESHOLD (V)
14
12
T
A
= –45°C
T
A
= 0°C
10
T
A
= 25°C
8
T
A
= 85°C
6
10
30
50
V
CC
(V)
70
90
1641-1 G10
ON Pin Voltage Hysteresis vs
Temperature
0.100
20
18
16
PWRGD V
OUT
LOW (V)
14
12
10
8
6
4
2
0.050
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
0
SENSE PIN REGULATION VOLTAGE (mV)
ON PIN LOW VOLTAGE HYSTERESIS (V)
V
CC
= 48V
0.090
0.080
0.070
0.060
4
U W
75
1641-1 G07
1641-1 G13
Gate Drive vs V
CC
–40
–50
–60
–70
–80
–90
TIMER Pin Pull Up Current vs
Temperature
V
CC
= 48V
14
T
A
= 25°C
12
10
8
–100
–110
–50
6
100
0
20
40
V
CC
(V)
60
80
1641-1 G08
–25
0
25
50
TEMPERATURE (°C)
75
100
1641-1 G09
ON Pin High Voltage Threshold vs
Temperature
1.335
V
CC
= 48V
1.239
1.237
1.235
1.233
1.231
1.229
1.227
1.225
ON Pin Low Voltage Threshold vs
Temperature
V
CC
= 48V
–25
0
25
50
TEMPERATURE (°C)
75
100
1.223
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1641-1 G11
1641-1 G12
PWRGD V
OUT
Low vs I
LOAD
50
V
CC
= 48V
45
40
35
30
25
20
15
10
5
0
10
30
50
I
LOAD
(mA)
70
90
1641-1 G14
SENSE Pin Regulation Voltage vs
V
FEEDBACK
V
CC
= 48V
T
A
= 25°C
T
A
= –45°C
T
A
= 25°C
T
A
= 85°C
0
0.2
0.4
0.6
V
FEEDBACK
(V)
0.8
1
1641-1 G15
164112fc
LT1641-1/LT1641-2
PI FU CTIO S
ON (Pin 1):
The ON pin is used to implement undervoltage
lockout. When the ON pin is pulled below the 1.233V High-
to-Low threshold voltage, an undervoltage condition is
detected and the GATE pin is pulled low to turn the
MOSFET off. When the ON pin rises above the 1.313V
Low-to-High threshold voltage, the MOSFET is turned on
again.
Pulsing the ON pin low after a current limit fault will reset
the fault latch and allow the part to turn back on.
FB (Pin 2):
Power Good Comparator Input. It monitors the
output voltage with an external resistive divider. When the
voltage on the FB pin is lower than the High-to-Low
threshold of 1.233V, the PWRGD pin is pulled low and
released when the FB pin is pulled above the 1.313V Low-
to-High threshold.
The FB pin also effects foldback current limit (see Figure 7
and related discussion).
PWRGD (Pin 3):
Open Collector Output to GND. The
PWRGD pin is pulled low whenever the voltage at the FB
pin falls below the High-to-Low threshold voltage. It goes
into a high impedance state when the voltage on the FB pin
exceeds the Low-to-High threshold voltage. An external
pull-up resistor can pull the pin to a voltage higher or lower
than V
CC
.
GND (Pin 4):
Chip Ground.
TIMER (Pin 5):
Timing Input. An external timing capacitor
at this pin programs the maximum time the part is allowed
to remain in current limit.
When the part goes into current limit, an 77µA pull-up
current source starts to charge the timing capacitor. When
the voltage on the TIMER pin reaches 1.233V, the GATE
pin is pulled low; the pull-up current will be turned off and
the capacitor is discharged by a 3µA pull-down current.
When the TIMER pin falls below 0.5V, the GATE pin either
turns on automatically (LT1641-2) or turns on once the
ON pin is pulsed low to reset the internal fault latch
(LT1641-1). If the ON pin is not cycled low, the GATE pin
remains latched off. Use no less than 1.5nF for the timing
capacitor, C2.
GATE (Pin 6):
The High Side Gate Drive for the External
N-Channel. An internal charge pump guarantees at least
10V of gate drive for supply voltages above 20V and 4.5V
gate drive for supply voltages between 10.8V and 20V. The
rising slope of the voltage at the GATE is set by an external
capacitor connected from the GATE pin to GND and an
internal 10µA pull-up current source from the charge
pump output.
When the current limit is reached, the GATE pin voltage will
be adjusted to maintain a constant voltage across the
sense resistor while the timer capacitor starts to charge.
If the TIMER pin voltage exceeds 1.233V, the GATE pin will
be pulled low.
The GATE pin is pulled to GND whenever the ON pin is
pulled low, the V
CC
supply voltage drops below the 8.3V
undervoltage lockout threshold or the TIMER pin rises
above 1.233V.
SENSE (Pin 7):
The Current Limit Sense Pin. A sense
resistor must be placed in the supply path between V
CC
and SENSE. The current limit circuit will regulate the
voltage across the sense resistor (V
CC
– V
SENSE
) to 47mV
when V
FB
is 0.5V or higher. If V
FB
drops below 0.5V, the
voltage across the sense resistor decreases linearly and
stops at 12mV when V
FB
is 0V.
To defeat current limit, short the SENSE pin to the V
CC
pin.
V
CC
(Pin 8):
The Positive Supply Input ranges from 9V to
80V for normal operation. I
CC
is typically 2mA. An internal
undervoltage lockout circuit disables the chip for inputs
less than 8.3V.
U
U
U
164112fc
5
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