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PDF LT4356MP-1 Data sheet ( Hoja de datos )
| Número de pieza | LT4356MP-1 | |
| Descripción | Surge Stopper | |
| Fabricantes | Linear | |
| Logotipo |  |
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LT4356MP-1/LT4356MP-2
Surge Stopper
FEATURES
n Stops High Voltage Surges
n Adjustable Output Clamp Voltage
n Overcurrent Protection
n Wide Operation Range: 4V to 80V
n Reverse Input Protection to –60V
n Low 7μA Shutdown Current, LT4356-1
n Adjustable Fault Timer
n Controls N-channel MOSFET
n Shutdown Pin Withstands –60V to 100V
n Fault Output Indication
n Guaranteed Operation –55°C to 125°C
n Auxiliary Amplifier for Level Detection Comparator or
Linear Regulator Controller
n Available in 10-Pin MSOP or 16-Pin SO Packages
APPLICATIONS
n Automotive/Avionic Surge Protection
n Hot Swap/Live Insertion
n High Side Switch for Battery Powered Systems
n Intrinsic Safety Applications
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. Hot Swap, No RSENSE and ThinSOT are trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
DESCRIPTION
The LT®4356 surge stopper protects loads from high voltage
transients. It regulates the output during an overvoltage
event, such as load dump in automobiles, by controlling
the gate of an external N-channel MOSFET. The output
is limited to a safe value thereby allowing the loads to
continue functioning. The LT4356MP also monitors the
voltage drop between the VCC and SNS pins to protect
against overcurrent faults. An internal amplifier limits the
current sense voltage to 50mV. In either fault condition, a
timer is started inversely proportional to MOSFET stress.
If the timer expires, the FLT pin pulls low to warn of an
impending power-down. If the condition persists, the
MOSFET is turned off. After a cooldown period, the GATE
pin pulls up turning on the MOSFET again.
The auxiliary amplifier may be used as a voltage detection
comparator or as a linear regulator controller driving an
external PNP pass transistor.
Back-to-back FETs can be used in lieu of a Schottky diode
for reverse input protection, reducing voltage drop and
power loss. A shutdown pin reduces the quiescent current
to less than 7μA for the LT4356-1 during shutdown. The
LT4356-2 differs from the LT4356-1 during shutdown by
reducing the quiescent current to 60μA and keeping alive
the auxiliary amplifier for uses such as an undervoltage
lockout or always-on regulator.
TYPICAL APPLICATION
4A, 12V Overvoltage Output Regulator
VIN
10mΩ IRLR2908
VOUT
12V
383k
100k
UNDERVOLTAGE
10Ω
VCC
SHDN
IN+
SNS GATE OUT
FB
LT4356S
AOUT
GND
EN
TMR FLT
4356mp12 TA01
0.1μF
102k
4.99k
VCC
DC-DC
CONVERTER
SHDN GND
FAULT
Overvoltage Protector Regulates Output at
27V During Transient
80V INPUT SURGE
VIN
20V/DIV
CTMR = 6.8μF
ILOAD = 500mA
12V
VOUT
20V/DIV
12V
27V ADJUSTABLE CLAMP
100ms/DIV
4356mp12 TA01b
4356mp12fb
1
1 page  
LT4356MP-1/LT4356MP-2
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are at VCC = 12V, TA = 25°C unless otherwise noted.
ICC (Shutdown) vs Temperature
35 LT4356-1
30
25
20
15
10
5
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4356mp12 G04
ICC (Shutdown) vs Temperature
300 LT4356-2
250
200
150
100
50
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4356mp12 G05
SHDN Current vs Temperature
6 VSHDN = 0V
5
4
3
2
1
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4356mp12 G06
GATE Pull-Up Current vs VCC
40
35
30
25
20
15
10
5
0
0 10 20 30 40 50 60 70 80
VCC (V)
4356mp12 G07
GATE Pull-Up Current
vs Temperature
35 VGATE = VOUT = 12V
30
25
20
15
10
5
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4356mp12 G08
GATE Pull-Down Current
vs Temperature
220 OVERVOLTAGE CONDITION
VFB = 1.5V
200
180
160
140
120
100
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4356mp12 G09
GATE Pull-Down Current
vs Temperature
12 OVERCURRENT CONDITION
ΔVSNS = 120mV
10
8
6
4
2
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4356mp12 G10
ΔVGATE vs IGATE
14
12
VOUT = 12V
10
8
6
4
2
0
0 2 4 6 8 10 12 14 16
IGATE (μA)
4356mp12 G11
ΔVGATE vs Temperature
14 IGATE = –1μA
12 VCC = 8V
10
8
6
VCC = 4V
4
2
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4356mp12 G12
4356mp12fb
5
5 Page 
LT4356MP-1/LT4356MP-2
APPLICATIONS INFORMATION
Fault Timer Current
The timer current starts at around 2μA with 0.5V or less
of VDS, increasing linearly to 50μA with 75V of VDS dur-
ing an overvoltage fault (Figure 1). During an overcurrent
fault, it starts at 4μA with 0.5V or less of VDS but increases
to 260μA with 80V across the MOSFET (Figure 2). This
arrangement allows the pass transistor to turn off faster
during an overcurrent event, since more power is dissipated
during this condition. Refer to the Typical Performance
Characteristics section for the timer current at different
VDS in both overvoltage and overcurrent events.
VTMR(V)
1.35
1.25
ITMR = 5μA
VDS = 75V
(ITMR = 50μA)
When the voltage at the TMR pin,
threshold, the FLT pin pulls low
VTMR, reaches
to indicate the
the 1.25V
detection
of a fault condition and provide warning to the load of
the impending power loss. In the case of an overvoltage
fault, the timer current then switches to a fixed 5μA. The
interval between FLT asserting low and the MOSFET turn-
ing off is given by:
t WARNING
=
CTMR • 100mV
5μA
ITMR = 5μA
VDS = 10V
(ITMR = 8μA)
0.50
tFLT
= 15ms/μF
tWARNING
= 20ms/μF
tFLT = 93.75ms/μF
TOTAL FAULT TIMER = tFLT + tWARNING
tWARNING
= 20ms/μF
Figure 1. Overvoltage Fault Timer Current
TIME
4356mp12 F01
VTMR(V)
1.35
1.25
VDS = 80V
(ITMR = 260μA)
VDS = 10V
(ITMR = 35μA)
0.50
tFLT
= 2.88ms/μF
tWARNING
= 0.38ms/μF
tFLT = 21.43ms/μF
TOTAL FAULT TIMER = tFLT + tWARNING
tWARNING
= 2.86ms/μF
Figure 2. Overcurrent Fault Timer Current
TIME
4356mp12 F02
4356mp12fb
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT4356MP-1.PDF ] | |
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