LT4256-1 Datasheet PDF - Linear Technology

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LT4256-1
Linear Technology

Part Number LT4256-1
Description (LT4256-1/-2) Positive High Voltage Hot Swap Controllers
Page 16 Pages


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LT4256-1/LT4256-2
Positive High Voltage
Hot Swap Controllers
FEATURES
Allows Safe Board Insertion and Removal from a
Live Backplane
Controls Supply Voltage from 10.8V to 80V
Foldback Current Limiting
Overcurrent Fault Detection
Drives an External N-Channel MOSFET
Programmable Supply Voltage Power-Up Rate
Undervoltage Protection
Latch Off Operation Mode (LT4256-1)
Automatic Retry (LT4256-2)
Available in an 8-Pin SO Package
U
APPLICATIO S
Hot Board Insertion
Electronic Circuit Breaker/Power Bussing
Industrial High Side Switch/Circuit Breaker
24V/48V Industrial/Alarm Systems
Ideally Suited for 12V, 24V and 48V Distributed
Power Systems
48V Telecom Systems
DESCRIPTIO
The LT®4256-1/LT4256-2 are high voltage Hot SwapTM
controllers that allow a board to be safely inserted and
removed from a live backplane. An internal driver drives an
external N-channel MOSFET switch to control supply
voltages ranging from 10.8V to 80V.
The LT4256-1/LT4256-2 features an adjustable analog
foldback current limit. If the supply remains in current limit
for more than a programmable time, the N-channel
MOSFET shuts off and the PWRGD output asserts low. The
LT4256-2 automatically restarts after a time-out delay.
The LT4256-1 latches off until the UV pin is cycled low.
The PWRGD output indicates when the output voltage
rises above a programmed level. An external resistor
string from VCC provides programmable undervoltage
protection.
The LT4256 can be used as an upgrade to LT1641 designs.
See Table 1 on page 14 for upgraded specifications.
The LT4256-1 and LT4256-2 are available in an 8-pin SO
package that is pin compatible with the LT1641.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
48V, 2A Hot Swap Controller
VIN
0.02
IRF530
48V SMAT70A
CMPZ5241B
(SHORT PIN)
87
11V
64.9k
VCC
1
UV
SENSE 10
6
GATE
10nF
100
36.5k
0.1µF
8.06k
LT4256-1/
LT4256-2
2
FB
4.02k
VOUT
48V
CL 2A
27k
VIN
50V/DIV
VOUT
50V/DIV
INRUSH
CURRENT
500mA/DIV
LT4256 Start-Up Behavior
5
TIMER
3
PWRGD
UV = 36V
PWRGD
4256 TA01
PWRGD CL = 225µF
50V/DIV
2.5ms/DIV
4256 TA02
GND
33nF GND
PWRGD = 40V
4
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LT4256-1/LT4256-2
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltage (VCC) ................................ – 0.3 to 100V
SENSE, PWRGD ....................................... – 0.3 to 100V
GATE (Note 2) ................................ – 0.3V to VCC + 10V
Maximum Input Current (GATE) ......................... 200µA
FB, UV ........................................................ – 0.3 to 44V
TIMER ..................................................... – 0.3V to 4.3V
Maximum Input Current (TIMER) ....................... 100µA
Operating Temperature
LT4256C ................................................. 0°C to 70°C
LT4256I ............................................. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
UV 1
FB 2
TOP VIEW
8 VCC
7 SENSE
LT4256-1CS8
LT4256-1IS8
LT4256-2CS8
LT4256-2IS8
PWRGD 3
6 GATE S8 PART MARKING
GND 4
5 TIMER
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 110°C/W
42561
42561I
42562
42562I
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.
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 48V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
VCC
ICC
VUVLH
VUVHYS
IINUV
Operating Voltage
Operating Current
Undervoltage Threshold
Hysteresis
UV Input Current
VCC Low-to-High Transition
UV 1.2V
UV = 0V
10.8
80
1.8 3.9
3.96 4 4.04
0.25 0.4 0.55
–0.1 –1
–1.5 –3
V
mA
V
V
µA
µA
VUVRTH
Fault Latch Reset Threshold Voltage
VSENSETRIP SENSE Pin Trip Voltage (VCC – VSENSE)
FB = 0V
FB 2V
0.4 0.85 1.2
5.5 14 22
45 55 65
V
mV
mV
IINSNS
IPU
IPD
VGATE
VFB
SENSE Pin Input Current
GATE Pull-Up Current
GATE Pull-Down Current
External N-Channel Gate Drive (Note 2)
FB Voltage Threshold
VSENSE = VCC
Charge Pump On, VGATE = 7V
Any Fault, VGATE = 3V
VGATE – VCC, 10.8V VCC 20V
20V VCC 80V
FB High-to-Low Transition
FB Low-to-High Transition
40 70
–16 – 32 – 63
40 62 80
4.5
10
8.8 12.5
11.6 12.8
3.95 3.99 4.03
4.2
4.45 4.65
µA
µA
mA
V
V
V
V
VFBHYS
VOLPGD
IPWRGD
IINFB
ITIMERPU
ITIMERPD
VTHTIMER
DTIMER
FB Hysteresis Voltage
PWRGD Output Low Voltage
PWRGD Pin Leakage Current
FB Input Current
TIMER Pull-Up Current
TIMER Pull-Down Current
TIMER Shut-Down Threshold
Duty Cycle (RETRY Mode)
IO = 1.6mA
IO = 5mA
VPWRGD = 80V
FB = 4.5V
TIMER = 3V, During Fault
TIMER = 3V
CTIMER = 10nF
0.3
– 63
1.5
4.3
1.5
0.45
0.25
0.6
0.1
–0.1
– 105
3
4.65
3
0.6
0.4
1
1
–1
– 147
5
5
4.5
V
V
V
µA
µA
µA
µA
V
%
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LT4256-1/LT4256-2
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 48V unless otherwise noted.
SYMBOL
tPHLUV
tPLHUV
tPHLFB
tPLHFB
tPHLSENSE
PARAMETER
UV Low to GATE Low
UV High to GATE High
FB Low to PWRGD Low
FB High to PWRGD High
(VCC – VSENSE) High to GATE Low
CONDITIONS
CGATE = 0
VCC – VSENSE = 275mV
MIN TYP MAX UNITS
1.7 3
µs
69
µs
0.8 2
µs
3.2 5
µs
13
µs
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: An internal clamp limits the GATE pin to a minimum of 10V above
VCC. Driving this pin to a voltage beyond the clamp voltage may damage
the part.
TYPICAL PERFOR A CE CHARACTERISTICS Specifications are at TA = 25°C unless
otherwise noted.
UV Thresholds vs Temperature
4.1
L-H THRESHOLD
4.0
3.9
3.8
3.7
H-L THRESHOLD
3.6
SENSE Pin Regulation Voltage
vs Temperature
58
53 FB > 2V
48
20
15 FB = 0V
ICC vs VCC
3.5
3.0
2.5
2.0
1.5
1.0
0.5
3.5
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G01
10
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G02
0
10 20 30 40 50 60 70 80
VCC (V)
4256 G03
ICC vs Temperature
2.5
VCC = 48V
2.0
1.5
1.0
0.5
PWRGD Thresholds
vs Temperature
4.5
L-H THRESHOLD
4.4
4.3
4.2
4.1
H-L THRESHOLD
4.0
PWRGD Output Voltage
vs IPWRGD
6
5
4
3
2
1
0
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G04
3.9
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G05
0
0 2 4 6 8 10 12
IPWRGD (mA)
4256 G06
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LT4256-1/LT4256-2
TYPICAL PERFOR A CE CHARACTERISTICS Specifications are at TA = 25°C unless
otherwise noted.
GATE Pin Pull-Up Current
vs Temperature
0
–5
–10
–15
–20
–25
–30
–35
–40
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G07
VGATE – VCC Voltage
vs Temperature
14
12 VCC = 18V
10
VCC = 12V
8
6 VCC = 10.8V
4
2
0
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G10
GATE Pin Pull-Down Current
vs Temperature
63
62
61
60
59
58
57
56
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G08
VGATE – VCC Voltage
vs Temperature
14.0
13.5
13.0
12.5
12.0
11.5 VCC = 80V
VCC = 20V
VCC = 48V
11.0
10.5
10.0
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G11
UV Pin Current vs UV Pin Voltage
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–1.2
–1.4
01234
20 30 40 50
VUV (V)
4256 G09
TIMER Pin Currents
vs Temperature
10
5 PULL-DOWN CURRENT
0
–80
–100
PULL-UP CURRENT
–120
–140
–50 –25
0
25 50
TEMPERATURE (°C)
75 100
4256 G12
TIMER Pin Currents vs VCC
5.0
PULL-DOWN CURRENT
2.5
0
–80
–100
PULL-UP CURRENT
–120
Timer Shutdown Threshold
vs Temperature
5.4
5.2
5.0
4.8
4.6
4.4
4.2
4
–140
10 20 30 40 50 60 70 80
VCC (V)
4256 G13
0
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
4256 G14
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