LT1641
Positive High Voltage
Hot Swap Controller
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
Automatic Retry Capability
User Programmable Supply Voltage Power-Up Rate
Undervoltage Lockout
Overvoltage Protection
Available in 8-Lead SO Package
The LT
®
1641 is an 8-pin Hot Swap
TM
controller that allows
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 program-
mable rate. A high side switch driver controls an N-channel
gate for supply voltages ranging from 9V to 80V.
The chip features a programmable analog foldback cur-
rent limit circuit. If the chip remains in current limit for
more than a programmable time, the N-channel pass
transistor turns off and is optionally set to automatically
restart after a time-out delay.
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 recommended for new
designs.
The LT1641 is 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 Automatic Restart Application
R
S
0.01Ω
Q1
IRF530
V
OUT
SHORT
PIN
R1
49.9k
1%
10nF
R7
24k
5%
FB
LT1641
R2
3.4k
1%
TIMER
C2
0.68µF
1641 TA01
R5
10Ω
5%
D1
CMPZ
5248B
R3
59k
1%
*SMAT70A
V
CC
ON
SENSE
GATE
R4
3.57k
1%
PWRGD
GND
GND
*DIODES, INC.
U
C
L
PWRGD
1641fd
U
U
1
LT1641
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
ON
1
FB
2
PWRGD
3
GND
4
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
LT1641CS8 ............................................. 0°C to 70°C
LT1641IS8 .......................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
8
7
6
5
V
CC
SENSE
GATE
TIMER
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 110°C/W
NOT RECOMMENDED FOR NEW DESIGNS
SEE LT1641-1/LT1641-2
ORDER PART NUMBER
LT1641CS8
LT1641IS8
S8 PART MARKING
1641
1641I
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
1641fd
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
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 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
0.095
0.090
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
FB PIN HYSTERESIS (V)
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 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
1641 G02
1.200
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1641 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
1641 G05
I
GATE
Pull Up vs Temperature
V
CC
= 48V
0.085
100
–13
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1641 G06
1641fd
3
LT1641
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
1.335
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 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
1641 G13
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 G07
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 G08
–25
0
25
50
TEMPERATURE (°C)
75
100
1641 G09
ON Pin High Voltage Threshold vs
Temperature
1.239
V
CC
= 48V
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
1641 G11
1.223
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1641 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 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
0.2
0.4
0.6
V
FEEDBACK
(V)
0.8
1
1641 G15
1641fd
LT1641
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.
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 80µA 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 turns
on once the ON pin is pulsed low. Use no less than 1.5nF
for the timing capacitor, C2.
By connecting a 0.01µF capacitor from the GATE pin to the
center tap of a resistive divider at the ON pin, the part
automatically restarts after a current limit fault. With a
short at the output, the part cycles on and off with a 3.75%
on-time duty cycle.
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
1641fd
5
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