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PDF LTC4365 Data sheet ( Hoja de datos )
| Número de pieza | LTC4365 | |
| Descripción | UV and OV and Reverse Supply Protection Controller | |
| Fabricantes | Linear Technology Corporation | |
| Logotipo |  |
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LTC4365
UV, OV and Reverse
Supply Protection Controller
FEATURES
n Wide Operating Voltage Range: 2.5V to 34V
n Overvoltage Protection to 60V
n Reverse Supply Protection to –40V
n Blocks 50Hz and 60Hz AC Power
n No Input Capacitor or TVS Required for Most
Applications
n Adjustable Undervoltage and Overvoltage
Protection Range
n Charge Pump Enhances External N-Channel MOSFET
n Low Operating Current: 125µA
n Low Shutdown Current: 10µA
n Fault Status Output
n Compact 8-Lead, 3mm × 2mm DFN and
TSOT-23 (ThinSOT™) Packages
APPLICATIONS
n Portable Instrumentation
n Industrial Automation
n Laptops
n Automotive
DESCRIPTION
The LTC®4365 protects applications where power supply
input voltages may be too high, too low or even negative.
It does this by controlling the gate voltages of a pair of
external N-channel MOSFETs to ensure that the output
stays within a safe operating range.
The LTC4365 can withstand voltages between –40V and
60V and has an operating range of 2.5V to 34V, while
consuming only 125µA in normal operation.
Two comparator inputs allow configuration of the
overvoltage (OV) and undervoltage (UV) set points using an
external resistive divider. A shutdown pin provides external
control for enabling and disabling the MOSFETs as well
as placing the device in a low current shutdown state. A
fault output provides status of the gate pin pulling low. A
fault is indicated when the part is in shutdown or the input
voltage is outside the UV and OV set points.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT, No RSENSE and Hot Swap are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
12V Automotive Application
VIN
12V
Si4946
VOUT
3A
510k
VIN GATE VOUT
LTC4365
1820k
243k
SHDN
UV
FAULT
OV
59k GND
4365 TA01a
OV = 18V
UV = 3.5V
www.DataSheet.in
Load Protected from Reverse and Overvoltage at VIN
UV = 3.5V
30V OV = 18V
VIN
VALID
WINDOW
GND
VOUT
VOUT
10V/DIV
–30V
VIN
1s/DIV
4365 TA01b
4365f
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC4365
UV Threshold vs Temperature
507.5
VIN = VOUT = 12V
505.0
502.5
500.0
497.5
495.0
492.5
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4365 G10
UV/OV Propagation Delay vs
Overdrive
20
VIN = VOUT = 12V
T = 25°C
16
12
OV Threshold vs Temperature
507.5
VIN = VOUT = 12V
505.0
502.5
500.0
497.5
495.0
492.5
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4365 G11
Recovery Delay Time vs
Temperature
50
40 VIN = 34V
VIN = 12V
30
8 20
VIN = 2.5V
4 10
00
1
10
100 1000
–50 –25 0 25 50 75 100 125
OVERDRIVE (mV)
TEMPERATURE (°C)
4365 G13
4365 G14
UV/OV Leakage vs Temperature
1.00
VUV/OV = 0.5V
VIN = 12V
0.75
0.50
0.25
0
–75
UV
OV
–25 25
75 125
TEMPERATURE (°C)
175
4365 G12
Recovery Delay Time vs VIN
50
–45°C
125°C
40
25°C
30
20
10
0
0 5 10 15 20 25 30 35
VIN (V)
4365 G15
AC Blocking
1V/DIV
VOUT
VIN
20V/DIV
GATE
Turn-On Timing
GND
5V/DIV
100µF, 12Ω LOAD ON VOUT
60V SI9945 DUAL NCH MOSFET
VIN = 12V
GND
VOUT
10µF, 1k LOAD ON VOUT
60V DUAL NCH MOSFET
2.5ms/DIV
4365 G16
3V/DIV SHDN
250µs/DIV
GATE
Turn-Off Timing
GATE
5V/DIV
VOUT
100µF, 12Ω LOAD ON VOUT
60V SI9945 DUAL NCH MOSFET
GND
GND 3V/DIV
4365 G17
SHDN
250µs/DIV
GND
GND
4365 G18
www.DataSheet.in
4365f
5
5 Page 
LTC4365
APPLICATIONS INFORMATION
The resistor values can then be solved:
1.
R1+ R2
=
3mV
10nA
= 300k
2.
R3
=
2
•
3mV
10nA
•
(3.5V
–
0.5V)
=
1.8M
The closest 1% value: R3 = 1.82M:
3.
R1 =
300k +1.82M
2 • 18V
=
58.9k
The closest 1% value: R1 = 59k:
R2 = 300k – 59k = 241k
The closest 1% value: R2 = 243k
Therefore: OV = 17.93V, UV = 3.51V.
Reverse VIN Protection
The LTC4365’s rugged and hot-swappable VIN input helps
protect the more sensitive circuits at the output load. If
the input supply is plugged in backwards, or a negative
supply is inadvertently connected, the LTC4365 prevents
this negative voltage from passing to the output load.
The LTC4365 employs a novel, high speed reverse sup-
ply voltage monitor. When the negative VIN voltage is
detected, an internal switch connects the gates of the
external back-to-back N-channel MOSFETs to the nega-
tive input supply.
As shown in Figure 6, external back-to-back N-channel
MOSFETs are required for reverse supply protection. When
VIN goes negative, the reverse VIN comparator closes the
internal switch, which in turn connects the gates of the
external MOSFETs to the negative VIN voltage. The body
diode (D1) of M1 turns on, but the body diode (D2) of M2
remains in reverse blocking mode. This means that the
common source connection of M1 and M2 remains about
a diode drop higher than VIN. Since the gate voltage of
M2 is shorted to VIN, M2 will be turned off and no cur-
rent can flow from VIN to the load at VOUT. Note that the
voltage rating of M2 must withstand the reverse voltage
excursion at VIN.
Figure 7 illustrates the waveforms that result when VIN
is hot plugged to –20V. VIN, GATE and VOUT start out at
ground just before the connection is made. Due to the
parasitic inductance of the VIN and GATE connections, the
voltage at the VIN and GATE pins ring significantly below
–20V. Therefore, a 40V N-channel MOSFET was selected
to survive the overshoot.
The speed of the LTC4365 reverse protection circuits is
evident by how closely the GATE pin follows VIN during
the negative transients. The two waveforms are almost
indistinguishable on the scale shown.
VIN = –40V
D1
M1
D2
+ TO LOAD
M2 COUT
GND
5V/DIV
VOUT
VIN
GATE
VOUT
REVERSE VIN
COMPARATOR
LTC4365
+
GND
– CLOSES SWITCH
WHEN VIN IS NEGATIVE
4365 F06
Figure 6. Reverse VIN Protection Circuits
–20V
GATE
VIN
500ns/DIV
4365 F07
Figure 7. Hot Swapping VIN to –20V
www.DataSheet.in
4365f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4365.PDF ] | |
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