LTC4364-1/LTC4364-2
Surge Stopper
with Ideal Diode
FEATURES
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DESCRIPTION
Wide Operating Voltage Range: 4V to 80V
Withstands Surges Over 80V with VCC Clamp
Adjustable Output Clamp Voltage
Ideal Diode Controller Holds Up Output Voltage
During Input Brownouts
Reverse Input Protection to –40V
Reverse Output Protection to –20V
Overcurrent Protection
Low 10μA Shutdown Current at 12V
Adjustable Fault Timer
0.1% Retry Duty Cycle During Faults (LTC4364-2)
Available in 4mm × 3mm 14-Lead DFN, 16-Lead MSOP,
and 16-Lead SO Packages
The LTC®4364 surge stopper with ideal diode controller
protects loads from high voltage transients. It limits and
regulates the output during an overvoltage event, such
as load dump in automobiles, by controlling the voltage
drop across an external N-channel MOSFET pass device.
The LTC4364 also includes a timed, current limited circuit
breaker. In a fault condition, an adjustable fault timer must
expire before the pass device is turned off. The LTC4364-1
latches off the pass device while the LTC4364-2 automatically restarts after a delay. The LTC4364 precisely monitors
the input supply for overvoltage (OV) and undervoltage
(UV) conditions. The external MOSFET is held off in undervoltage and auto-retry is disabled in overvoltage.
APPLICATIONS
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An integrated ideal diode controller drives a second MOSFET to replace a Schottky diode for reverse input protection and output voltage holdup. The LTC4364 controls the
forward voltage drop across the MOSFET and minimizes
reverse current transients upon power source failure,
brownout or input short.
Automotive/Avionic Surge Protection
Hot Swap/Live Insertion
Redundant Supply ORing
Output Port Protection
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Overvoltage Protector Regulates
Output at 27V During Input Transient
4A, 12V Overvoltage Output Regulator with Ideal Diode
Withstands 200V 1ms Transient at VIN
FDB33N25
VIN
12V
2.2k 6.8nF
VCC
SHDN
OV
60V
10mΩ
+
383k
CMZ5945B
68V
UV
6V
FDB3682
22µF
VOUT
CLAMPED
AT 27V
10Ω
OUT
FB
ENABLE
FAULT
FLT
TMR
27V CLAMP (ADJUSTABLE)
50ms/DIV
102k
ENOUT
OV
GND
12V
4364 TA01b
Ideal Diode Holds Up Output
During Input Short
4.99k
LTC4364
90.9k
CTMR = 6.8µF
ILOAD = 0.5A
VIN
20V/DIV
VOUT
20V/DIV 12V
HGATE SOURCE DGATE SENSE
UV
10k
92V INPUT SURGE
12V
VIN
10V/DIV
INPUT SHORTED
TO GND
CLOAD = 6300µF
ILOAD = 0.5A
436412 TA01a
0.22µF
VOUT 12V
10V/DIV
OUTPUT HELD UP
1ms/DIV
4364 TA01c
436412f
1
LTC4364-1/LTC4364-2
ABSOLUTE MAXIMUM RATINGS (Notes 1, 2)
Supply Voltage: VCC .................................. –40V to 100V
SOURCE, OV, UV, SHDN Voltages.............. –40V to 100V
DGATE, HGATE Voltages
(Note 3)...................... SOURCE – 0.3V to SOURCE + 10V
ENOUT, FLT Voltages................................. –0.3V to 100V
OUT, SENSE Voltages.................................–20V to 100V
Voltage Difference (SENSE to OUT)............. –30V to 30V
Voltage Difference (OUT to VCC)...............–100V to 100V
Voltage Difference (SENSE to SOURCE)...–100V to 100V
FB, TMR Voltages...................................... –0.3V to 5.5V
Operating Ambient Temperature Range
LTC4364C................................................. 0°C to 70°C
LTC4364I..............................................–40°C to 85°C
LTC4364H........................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MS, SO Packages.............................................. 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
OUT
1
14 FB
SENSE
2
13 TMR
DGATE
3
12 ENOUT
SOURCE
4
15
11 FLT
HGATE
5
10 GND
VCC
6
9 OV
SHDN
7
8 UV
OUT 1
TOP VIEW
OUT
SENSE
NC
DGATE
SOURCE
HGATE
NC
VCC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
FB
TMR
ENOUT
FLT
GND
OV
UV
SHDN
MS PACKAGE
16-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 120°C/W
DE PACKAGE
14-LEAD (4mm × 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 45°C/W
EXPOSED PAD (PIN 15) PCB GND CONNECTION OPTIONAL
SENSE 2
NC 3
DGATE 4
SOURCE 5
16 FB
15 TMR
14 ENOUT
13 FLT
12 GND
HGATE 6
11 OV
NC 7
10 UV
VCC 8
9
SHDN
S PACKAGE
16-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 100°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4364CDE-1#PBF
LTC4364CDE-1#TRPBF
43641
14-Lead (4mm × 3mm) Plastic DFN
0°C to 70°C
LTC4364IDE-1#PBF
LTC4364IDE-1#TRPBF
43641
14-Lead (4mm × 3mm) Plastic DFN
–40°C to 85°C
LTC4364HDE-1#PBF
LTC4364HDE-1#TRPBF
43641
14-Lead (4mm × 3mm) Plastic DFN
–40°C to 125°C
LTC4364CDE-2#PBF
LTC4364CDE-2#TRPBF
43642
14-Lead (4mm × 3mm) Plastic DFN
0°C to 70°C
LTC4364IDE-2#PBF
LTC4364IDE-2#TRPBF
43642
14-Lead (4mm × 3mm) Plastic DFN
–40°C to 85°C
LTC4364HDE-2#PBF
LTC4364HDE-2#TRPBF
43642
14-Lead (4mm × 3mm) Plastic DFN
–40°C to 125°C
LTC4364CMS-1#PBF
LTC4364CMS-1#TRPBF
43641
16-Lead Plastic MSOP
0°C to 70°C
LTC4364IMS-1#PBF
LTC4364IMS-1#TRPBF
43641
16-Lead Plastic MSOP
–40°C to 85°C
LTC4364HMS-1#PBF
LTC4364HMS-1#TRPBF
43641
16-Lead Plastic MSOP
–40°C to 125°C
LTC4364CMS-2#PBF
LTC4364CMS-2#TRPBF
43642
16-Lead Plastic MSOP
0°C to 70°C
LTC4364IMS-2#PBF
LTC4364IMS-2#TRPBF
43642
16-Lead Plastic MSOP
–40°C to 85°C
LTC4364HMS-2#PBF
LTC4364HMS-2#TRPBF
43642
16-Lead Plastic MSOP
–40°C to 125°C
436412f
2
LTC4364-1/LTC4364-2
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4364CS-1#PBF
LTC4364CS-1#TRPBF
LTC4364S-1
16-Lead Plastic SO
0°C to 70°C
LTC4364IS-1#PBF
LTC4364IS-1#TRPBF
LTC4364S-1
16-Lead Plastic SO
–40°C to 85°C
LTC4364HS-1#PBF
LTC4364HS-1#TRPBF
LTC4364S-1
16-Lead Plastic SO
–40°C to 125°C
LTC4364CS-2#PBF
LTC4364CS-2#TRPBF
LTC4364S-2
16-Lead Plastic SO
0°C to 70°C
LTC4364IS-2#PBF
LTC4364IS-2#TRPBF
LTC4364S-2
16-Lead Plastic SO
–40°C to 85°C
LTC4364HS-2#PBF
LTC4364HS-2#TRPBF
LTC4364S-2
16-Lead Plastic SO
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL
CHARACTERISTICS
The
l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 12V.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
80
V
750
µA
VCC
Operating Supply Range
ICC
Supply Current
VCC = SOURCE = SENSE = OUT = 12V, No Fault
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370
ICC(SHDN)
Supply Current in Shutdown
Shutdown
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10
50
μA
ICC(REV)
Reverse Input Current
VCC = −30V
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0
–10
μA
∆VHGATE
HGATE Gate Drive, (VHGATE − VSOURCE)
VCC = 4V, DGATE Low, IHGATE = 0µA, −1µA
VCC = 8V to 80V, DGATE Low, IHGATE = 0µA, −1µA
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l
5
10
7
12
9
16
V
V
IHGATE(UP)
HGATE Pull-Up Current
VCC = HGATE = DGATE = SOURCE = 12V
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–10
–20
–30
µA
IHGATE(DN)
HGATE Pull-Down Current
Overvoltage: FB = 1.5V, ∆VHGATE = 5V
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60
130
mA
Overcurrent: ∆VSNS = 100mV, ∆VHGATE = 5V
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60
130
mA
0.4
l
4
Surge Stopper
Shutdown/Fault Turn-Off: ∆VHGATE = 5V
l
ISRC
SOURCE Input Current
VCC = SOURCE = SENSE = OUT = 12V
VCC = SOURCE = 12V, Shutdown
VSOURCE = –30V
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l
l
VFB
FB Servo Voltage
VCC = 12V to 80V
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1
mA
18
32
–2.0
40
90
–3.5
µA
µA
mA
1.22
1.25
1.28
V
0
1
µA
45
43
18
50
50
25
55
57
32
mV
mV
mV
55
–2
110
–4
µA
mA
IFB
FB Input Current
FB = 1.25V
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∆VSNS
Overcurrent Fault Threshold,
(VSENSE – VOUT)
VCC = 4V to 80V, OUT = 2.5V to VCC, 0°C to 125°C
VCC = 4V to 80V, OUT = 2.5V to VCC, –40°C to 125°C
VCC = 4V to 80V, OUT = 0V to 1.5V
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l
ISNS
SENSE Input Current
SENSE = VCC = SOURCE = OUT = 12V
SENSE = –15V
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l
ITMR(UP)
TMR Pull-Up Current, Overvoltage
TMR = 1V, FB = 1.5V, VCC – OUT = 0.5V
TMR = 1V, FB = 1.5V, VCC – OUT = 75V
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–1.3
–40
–2.2
–50
–3
–60
µA
µA
TMR Pull-Up Current, Overcurrent
TMR = 1V, ∆VSNS = 60mV, VCC – OUT = 0.5V
TMR = 1V, ∆VSNS = 60mV, VCC – OUT = 75V
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l
–6
–210
–10
–260
–14
–310
µA
µA
TMR Pull-Up Current, Warning
TMR = 1.3V, FB = 1.5V, VCC – OUT = 0.5V
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–3
–5
–7
µA
TMR Pull-Up Current, Retry
TMR = 1V, FB = 1.5V
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–1.3
–2
–3
µA
ITMR(DN)
TMR Pull-Down Current
TMR = 1V, FB = 1.5V, Retry
Shutdown
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1.1
0.3
2
0.75
2.7
1.5
µA
mA
VTMR(F)
TMR Fault Threshold
FLT Falling, VCC = 4V to 80V
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1.22
1.25
1.28
V
VTMR(G)
TMR Gate Off Threshold
HGATE Falling, VCC = 4V to 80V
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1.32
1.35
1.38
V
436412f
3
LTC4364-1/LTC4364-2
ELECTRICAL
CHARACTERISTICS
The
l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 12V.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VTMR(R)
TMR Retry Threshold
HGATE Rising (After 32 Cycles), VCC = 4V to 80V
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0.125
0.15
0.175
V
∆VTMR
Early Warning Timer Window
VTMR(G) – VTMR(F), VCC = 4V to 80V
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75
100
125
UV Falling, VCC = 4V to 80V
l
1.22
1.25
1.28
l
25
50
80
mV
mV
VUV
UV Input Threshold
VUV(HYST)
UV Input Hysteresis
VUV(RST)
UV Reset Threshold
UV Falling, VCC = 4V to 80V, LTC4364-1 Only
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0.5
0.6
0.7
V
VOV
OV Input Threshold
OV Rising, VCC = 4V to 80V
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1.22
1.25
1.28
V
V
VOV(HYST)
OV Input Hysteresis
IIN
UV, OV Input Current
UV, OV = 1.25V
UV, OV = –30V
l
l
0
–0.3
1
–0.6
µA
mA
VOL
ENOUT, FLT Output Low
ISINK = 0.25mA
ISINK = 2mA
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l
0.1
0.5
0.3
1.3
V
V
ILEAK
ENOUT, FLT Leakage Current
ENOUT, FLT = 80V
l
0
2.5
µA
∆VOUT(TH)
Out High Threshold (VCC – VOUT)
ENOUT from Low to High
l
0.4
0.7
1
V
VOUT(RST)
Out Reset Threshold
ENOUT from High to Low
l
1.4
2.2
3
V
IOUT
OUT Input Current
VCC = OUT = 12V, SHDN Open
OUT = –15V
l
l
40
–4
80
–8
µA
mA
Output Current in Shutdown, ISNS + IOUT
VCC = SOURCE = SENSE = OUT = 12V, Shutdown
l
VSHDN
SHDN Input Threshold
VCC = 4V to 80V
l
0.5
VSHDN(FLT)
SHDN Pin Float Voltage
VCC = 12V to 80V
l
ISHDN
SHDN Input Current
SHDN = 0.5V
Maximum Allowable Leakage, VCC = 4V
SHDN = –30V
l
12
mV
12
40
µA
1.6
2.2
V
2.3
4
6.5
V
–1
l
–3.3
–1.5
–120
–300
µA
µA
µA
FB = 1.5V, VCC = 80V, OUT = 16V
∆VSNS = 60mV, VCC – OUT = 12V
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l
0.125
0.075
0.2
0.12
%
%
tOFF,HGATE(UV) Undervoltage to HGATE Low Propagation
Delay
UV Steps from 1.5V to 1V
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1.3
4
μs
tOFF,HGATE(OV) Overvoltage to HGATE Low Propagation
Delay
FB Steps from 1V to 1.5V
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0.25
1
μs
tOFF,HGATE(OC) Overcurrent to HGATE Low Propagation
Delay
∆VSNS Steps from 0mV to 150mV, OUT = 0V
l
0.5
2
μs
D
Retry Duty Cycle, Overvoltage
Retry Duty Cycle, Output Short
Ideal Diode
ΔVDGATE
DGATE Gate Drive, (VDGATE − VSOURCE)
VCC = 4V, No Fault, IDGATE = 0µA, −1µA
VCC = 8V to 80V, No Fault, IDGATE = 0µA, −1µA
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l
5
10
8.5
12
12
16
V
V
IDGATE(UP)
DGATE Pin Pull-Up Current
DGATE = SOURCE = VCC = 12V, ∆VSD = 0.1V
l
–5
–10
–15
µA
IDGATE(DN)
DGATE Pin Pull-Down Current
∆VDGATE = 5V, ∆VSD = –0.2V
∆VDGATE = 5V, Shutdown/Fault Turn-Off
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l
60
0.4
130
1
∆VSD
Ideal Diode Regulation Voltage,
(VSOURCE − VSENSE)
∆VDGATE = 2.5V, VCC = SOURCE = 12V
∆VDGATE = 2.5V, VCC = SOURCE = 4V
l
l
10
24
30
48
45
72
mV
mV
tOFF(DGATE)
DGATE Turn-Off Propagation Delay
∆VSD Steps from 0.1V to –1V
l
0.35
1.5
μs
Note 1: Stress 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 and all currents out
of device pins are negative. All voltages are referenced to GND unless
otherwise specified.
mA
mA
Note 3: Internal clamps limit the HGATE and DGATE pins to minimum of
10V above the SOURCE pin. Driving these pins to voltages beyond the
clamp may damage the device.
436412f
4
LTC4364-1/LTC4364-2
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs VCC
VCC = SOURCE = SENSE = OUT
400
300
250
200
ISNS + IOUT
150
SHDN = 0
12
OUT = 0
40
30
20
OUT = VCC
10
50
0
10
20
40
30
50
60
70
0
80
20
10
0
30
40 50
VCC (V)
60
OUT = 0
8
OUT = 12V
6
ISNS + IOUT in Shutdown vs VCC
100
70
0
–50 –25
80
–24
SOURCE = VCC
HGATE = DGATE = SOURCE = VCC
∆VSD = 100mV
20
12
∆VHGATE (V)
IGATE(UP) (µA)
40
DGATE
–8
–4
20
30
40
50
60
70
0
80
4
8
6
10
VCC (V)
12 20
VCC (V)
40
9
60
6
80
0
–10
–5
–15
436412 G05
436412 G06
∆VHGATE vs VIN in Figure 1
∆VDGATE vs IDGATE
VCC = 12V
13
–20
IHGATE (µA)
436412 G04
14
10
7
SNS = OUT = 12V
10
11
8
SNS = OUT = 24V
0
VCC = 12V
13
–16
–12
125
∆VHGATE vs IHGATE
14
HGATE
60
100
436412 G03
GATE Pull-Up Current vs VCC
–20
80
SNS = OUT = 48V
75
50
25
TEMPERATURE (°C)
0
436412 G02
436412 G01
ISNS + IOUT IN SHUTDOWN (µA)
10
2
ISRC
VCC (V)
0
SHDN = 0
VCC = 12V
14
4
100
0
ICC(SHDN) vs Temperature
16
50
ICC
350
ICC(SHDN) (µA)
SUPPLY CURRENT (µA)
ICC(SHDN) vs VCC
60
ICC(SHDN) (µA)
450
∆VDGATE vs VIN in Figure 1
14
14
12
12
10
10
10
9
∆VDGATE (V)
11
∆VHGATE (V)
∆VDGATE (V)
12
8
6
4
7
6
0
–2
–6
–4
IDGATE (µA)
–8
–10
436412 G07
2
6
R4 IN FIGURE 1
0Ω
2.2k
4.7k
10k
8
4
8
12
16
VIN (V)
20
8
R4 IN FIGURE 1
0Ω
2.2k
4.7k
10k
4
24
436412 G08
2
4
8
12
16
VIN (V)
20
24
436412 G09
436412f
5
LTC4364-1/LTC4364-2
TYPICAL PERFORMANCE CHARACTERISTICS
HGATE Pull-Down Current
vs Temperature
175
150
125
100
75
150
125
50
25
75
0
TEMPERATURE (°C)
100
50
25
75
0
TEMPERATURE (°C)
100
10
125
–60
–200
–150
–100
–50
20
30 40 50
VCC – VOUT (V)
60
70
0
80
0
10
20
30 40 50
VCC – VOUT (V)
60
70
0
10
20
30 40 50
VCC – VOUT (V)
60
70
80
VCC = 4V
50
35
∆VSD (mV)
∆VSD (mV)
VOL (V)
0.2
60
40
1.00
30
25
20
0
OVERCURRENT CONDITION
OUT = 0V
0.3
Ideal Diode Regulation Voltage
vs Temperature
45
1.25
0.25
0.4
436412 G15
50
VCC = 12V
0.50
OVERVOLTAGE CONDITION
OUT = 16V
0.5
0
80
Ideal Diode Regulation Voltage
vs VCC
0.75
0.6
436412 G14
EN, FLT Output Low vs Current
3.5 4.0
0.1
436412 G13
1.50
3.0
0.7
RETRY DUTY CYCLE (%)
ITMR(UP) (µA)
–10
10
1.5 2.0 2.5
VOUT (V)
0.8
OVERCURRENT CONDITION
OUT = 5V
–250 TMR = 1V
–20
1.0
Retry Duty Cycle vs VCC – VOUT
(LTC4364-2 Only)
–300
OVERVOLTAGE CONDITION
OUT = 5V
–50 TMR = 1V
–30
0.5
436412 G12
Overcurrent TMR Current
vs VCC – VOUT
–40
0
436412 G11
Overvoltage TMR Current
vs VCC – VOUT
0
30
20
50
–50 –25
125
40
100
436412 G10
ITMR(UP) (µA)
50
75
50
–50 –25
0
60
VSENSE – VSOURCE = 200mV
VCC = 12V
∆VDGATE = 5V
175
IDGATE(DN) (mA)
IHGATE(DN) (mA)
200
∆VSNS = 100mV OR FB = 1.5V
∆VHGATE = 5V
VCC = 12V
Overcurrent Threshold
vs OUT Voltage
∆VSNS (mV)
200
DGATE Pull-Down Current
vs Temperature
40
VCC = 12V
30
20
15
0
1
2
3
CURRENT (mA)
4
5
10
4
6
8
10
12
20
40
60
80
VCC (V)
436412 G16
436412 G17
10
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
436412 G18
436412f
6
LTC4364-1/LTC4364-2
PIN FUNCTIONS
DGATE: Diode Controller Gate Drive Output. When the load
current creates more than 30mV of drop across the MOSFET,
the DGATE pin is pulled high by an internal charge pump
current source and clamped to 12V above the SOURCE pin.
When the load current is small, the DGATE pin is actively
driven to maintain 30mV across the MOSFET. If reverse
current develops, a 130mA fast pull-down circuit quickly
connects the DGATE pin to the SOURCE pin, turning off
the MOSFET. Connect to SOURCE or leave open if unused.
ENOUT: Enable Output. An open-drain output that goes
high impedance when the voltage at the OUT pin is above
(VCC − 0.7V), indicating the external MOSFETs are fully
on. The state of the pin is latched and resets when the
OUT pin drops below 2.2V. The internal FET is capable of
sinking up to 2mA and can withstand up to 80V. Connect
to GND if unused.
Exposed Pad (DE Package Only): Exposed pad may be
left open or connected to device ground (GND).
FB: Voltage Regulator Feedback Input. Connect this pin to
the resistive divider connected between the OUT pin and
ground. During an overvoltage condition, the HGATE pin
is controlled to maintain 1.25V at the FB pin. Connect to
GND to disable the overvoltage clamp.
FLT: Fault Output. An open-drain output that pulls low
after the TMR pin reaches the warning threshold of 1.25V.
It indicates the pass device controlled by the HGATE pin
is about to turn off because either the supply voltage has
stayed at an elevated level for an extended period of time
(overvoltage fault) or the device is in an overcurrent condition (overcurrent fault). The internal FET is capable of
sinking up to 2mA and can withstand up to 80V. Connect
to GND if unused.
GND: Device Ground.
HGATE: Surge Stopper Gate Drive Output. The HGATE pin
is pulled up by an internal charge pump current source and
clamped to 12V above the SOURCE pin. Both voltage and
current amplifiers control the HGATE pin to regulate the
output voltage and limit the current through the MOSFET.
OUT: Output Voltage Sense Input. This pin senses the
voltage at the drain of the external N-channel MOSFET
connected to the DGATE pin. The voltage difference
between VCC and OUT sets the fault timer current. When
this difference drops below 0.7V, the ENOUT pin goes
high impedance.
OV: Overvoltage Comparator Input. When OV is above
its threshold of 1.25V, the fault retry function is inhibited.
When OV falls below its threshold, the HGATE pin is allowed to turn back on when fault conditions are cleared. At
power-up, an OV voltage higher than its threshold blocks
turn-on of the external N-channel MOSFET controlled by
the HGATE pin (see Applications Information). Connect
to GND if unused.
SENSE: Current Sense Input. Connect this pin to the input
side of the current sense resistor. The current limit circuit
controls the HGATE pin to limit the sense voltage between
the SENSE and OUT pins to 50mV if OUT is above 2.5V.
When OUT drops below 1.5V, the sense voltage is reduced
to 25mV for additional protection during an output short.
The sense amplifier also starts a current source to charge
up the TMR pin. The voltage difference between SENSE
and OUT must be limited to less than 30V. Connect to
OUT if unused.
SHDN: Shutdown Control Input. Pulling the SHDN pin
below 0.5V shuts off the LTC4364 and reduces the VCC pin
current to 10μA. Pull this pin above 2.2V or disconnect it
to allow the internal current source to turn the part back
on. When left open, the SHDN voltage is internally clamped
to 4V. The leakage current to ground at the pin should be
limited to no more than 1μA if no pull-up device is used to
turn the part on. The SHDN pin can be pulled up to 100V
or below GND by 40V without damage.
SOURCE: Common Source Input and Gate Drive Return.
Connect this pin directly to the sources of the external
back-to-back N-channel MOSFETs. SOURCE is the anode
of the ideal diode and the voltage sensed between this pin
and the SENSE pin is used to control the source-drain
voltage across the N-channel MOSFET (forward voltage
of the ideal diode).
436412f
7
LTC4364-1/LTC4364-2
PIN FUNCTIONS
TMR: Fault Timer Input. Connect a capacitor between this
pin and ground to set the times for fault warning, fault
turn-off, and cool down periods. Either voltage regulation
or current regulation starts pulling up the TMR pin. The
current charging up this pin during the fault conditions
increases with the voltage difference between VCC and OUT
pins (see Applications Information). When TMR reaches
1.25V, the FLT pin pulls low to indicate the detection of a
fault condition. If the condition persists, the pass device
controlled by HGATE turns off when TMR reaches the
threshold of 1.35V. As soon as the fault condition disappears, a cool down interval commences while the TMR
pin cycles 32 times between 0.15V and 1.35V with 2μA
charge and discharge currents. When TMR crosses 0.15V
the 32nd time, the HGATE pin is allowed to pull high turning the pass device back on if the OV pin voltage is below
its threshold for the LTC4364-2 version. The HGATE pin
latches low after fault time-out for the LTC4364-1.
UV: Undervoltage Comparator Input. When the UV pin
falls below its 1.25V threshold, the HGATE pin is pulled
down with a 1mA current. When the UV pin rises above
1.25V plus the hysteresis, the HGATE pin is pulled up by
the internal charge pump. For LTC4364-1, after HGATE
is latched off, pulling the UV pin below 0.6V resets the
latch and allows HGATE to retry. If unused, connect to
the SHDN pin.
VCC: Positive Supply Voltage Input. The positive supply
input ranges from 4V to 80V for normal operation. It can
also be pulled below ground potential by up to 40V during
a reverse battery condition, without damaging the part.
Shutting down the LTC4364 by pulling the SHDN pin to
ground reduces the VCC current to 10μA.
436412f
8
LTC4364-1/LTC4364-2
BLOCK DIAGRAM
VCC
SOURCE
HGATE
HGATE OFF
10µA
CHARGE
PUMP
f = 620kHz
DGATE
12V
12V
SENSE
DGATE OFF
20µA
FD
–
VA
–
IA
+
–
1.25V
+
–
+
+
–
DA
+
+
–
+
–
30mV
30mV
50mV/
25mV
OUT
FB
SHDN
–
OC
ENOUT SET
OV
ENOUT RESET
SHDN
+
UVIN
RETRY
OV
–
1.35V
+
0.15V
VCC
–
CONTROL
CIRCUITRY
VCC – 0.7V
+
1.25V
+
–
UV
–
+
2.2V
FLT
+
32x
ENOUT
–
+
2µA
1.25V
TMR
–
GND
436412 BD
436412f
9
LTC4364-1/LTC4364-2
OPERATION
The LTC4364 is designed to suppress high voltage surges
and limit the output voltage to protect load circuitry and
ensure normal operation in high availability power systems.
It features an overvoltage protection regulator that drives
an external N-channel MOSFET (M1) as the pass device
and an ideal diode controller that drives a second external
N-channel MOSFET (M2) for reverse input protection and
output voltage holdup.
The LTC4364 operates from a wide range of supply voltage,
from 4V to 80V. With a clamp limiting the VCC supply, the
input voltage may be higher than 80V. The input supply
can also be pulled below ground potential by up to 40V
without damaging the LTC4364. The low power supply
requirement of 4V allows it to operate even during cold
cranking conditions in automotive applications.
Normally, the pass device M1 is fully on, supplying current
to the load with very little power loss. If the input voltage
surges too high, the voltage amplifier (VA) controls the gate
of M1 and regulates the voltage at the OUT pin to a level
that is set by an external resistive divider from the OUT pin
to ground and the internal 1.25V reference. The LTC4364
also detects an overcurrent condition by monitoring the
voltage across an external sense resistor placed between
the SENSE and OUT pins. An active current limit circuit
(IA) controls the gate of M1 to limit the sense voltage to
50mV if OUT is above 2.5V. In the case of a severe output
short that brings OUT below 1.5V, the sense voltage is
reduced to 25mV to reduce the stress on M1.
During an overvoltage or overcurrent event, a current
source starts charging up the capacitor connected at
the TMR pin to ground. The pull-up current source in
overcurrent condition is 5 times of that in overvoltage to
accelerate turn-off. When TMR reaches 1.25V, the FLT pin
pulls low to warn of impending turn-off. The pass device
M1 stays on and the TMR pin is further charged up until it
reaches 1.35V, at which point the HGATE pin pulls low and
turns off M1. The fault timer allows the load to continue
functioning during brief transient events while protecting
the MOSFET from being damaged by a long period of input
overvoltage, such as load dump in vehicles. The fault timer
period decreases with the voltage across the MOSFET,
to help keep the MOSFET within its safe operating area
(SOA). The LTC4364-1 latches off M1 and keeps FLT low
after a fault timeout. The LTC4364-2 allows M1 to turn
back on and FLT to go high impedance after a cool down
timer cycle, provided the OV pin is below its threshold.
After the HGATE pin is latched low following fault, momentarily pulling the SHDN pin below 0.5V resets the fault
and allows HGATE to pull high for both LTC4364-1 and
LTC4364‑2. In addition, momentarily pulling the UV pin
below 0.6V allows HGATE to pull high after the cool down
timer delay for LTC4364-1, but has no effect on LTC4364‑2.
The source and drain of MOSFET M2 serve as the anode
and cathode of the ideal diode. The LTC4364 controls the
DGATE pin to maintain a 30mV forward voltage across the
drain and source terminals of M2. It reduces the power
dissipation and increases the available supply voltage to
the load, as compared to using a discrete blocking diode.
If M2 is driven fully on and the load current results in
more than 30mV of forward voltage, the forward voltage
is equal to RDS(ON) • ILOAD.
In the event of an input short or a power supply failure,
reverse current temporarily flows through the MOSFET
M2 that is on. If the reverse voltage exceeds –30mV, the
LTC4364 pulls the DGATE pin low strongly and turns off
M2, minimizing the disturbance at the output.
If the input supply drops below the GND pin voltage, the
DGATE pin is pulled to the SOURCE pin voltage, keeping
M2 off. When the HGATE pin pulls low in any fault condition, the DGATE pin also pulls low, so both pass devices
are turned off.
If the output (and so the SOURCE pin, through the body
diode of M2) drops below GND, the HGATE pin is pulled
to the SOURCE pin voltage, turning M1 off and shutting
down the forward current path.
An input undervoltage condition is accurately detected
using the UV pin. The HGATE and DGATE pins remain low
if UV is below its 1.25V threshold. The SHDN pin not only
turns off the pass devices but also shuts down the internal
circuitry, reducing the supply current to 10µA.
436412f
10
LTC4364-1/LTC4364-2
APPLICATIONS INFORMATION
Some power systems must cope with high voltage surges
of short duration such as those in automobiles. Load
circuitry must be protected from these transients, yet
critical systems may need to continue operating during
these events.
If the voltage regulation loop is engaged for longer than
the timeout period, set by the timer capacitor, an overvoltage fault is detected. The HGATE pin is pulled down to the
SOURCE pin by a 130mA current, turning M1 off. This
prevents M1 from being damaged during a long period
of overvoltage, such as during load dump in automobiles.
After the fault condition has disappeared and a cool down
period has transpired, the HGATE pin starts to pull high
again (LTC4364-2). The LTC4364-1 latches the HGATE pin
low after an overvoltage fault timeout and can be reset
using the SHDN or UV pin (see Resetting Faults).
The LTC4364 drives an N-channel MOSFET (M1) at the
HGATE pin to limit the voltage and current to the load circuitry during supply transients or overcurrent events. The
selection of M1 is critical for this application. It must stay
on and provide a low impedance path from the input supply to the load during normal operation and then dissipate
power during overvoltage or overcurrent conditions. The
LTC4364 also drives a second N-channel MOSFET (M2) at
the DGATE pin as an ideal diode to protect the load from
damage during reverse polarity input conditions, and to
block reverse current flow in the event the input collapses.
A typical application circuit using the LTC4364 to regulate
the output at 27V during input surges with reverse input
protection is shown in Figure 1.
Overcurrent Fault
The LTC4364 features an adjustable current limit that
protects against short circuits and excessive load current.
During an overcurrent event, the HGATE pin is regulated
to limit the current sense voltage across the SENSE and
OUT pins (∆VSNS) to 50mV when OUT is above 2.5V. The
current limit sense voltage is reduced to 25mV when OUT is
below 1.5V for additional protection during an output short.
Overvoltage Fault
A current sense resistor is placed between SENSE and
OUT and its value (RSNS) is determined by:
The LTC4364 limits the voltage at the OUT pin during an
overvoltage situation. An internal voltage amplifier regulates the HGATE pin voltage to maintain 1.25V at the FB
pin. During this period of time, the N-channel MOSFET
M1 remains on and supplies current to the load. This
allows uninterrupted operation during brief overvoltage
transient events.
MAX DC:
100V/–24V VIN
MAX 1ms 12V
TRANSIENT:
200V
RSNS =
where ILIM is the desired current limit.
M1
FDB33N25
D4
SMAJ24A
D3
1.5KE200A
R1
383k
1%
R2
90.9k
1%
R3
10k
1%
R4
2.2k
0.5W
C1
0.1µF
M2
FDB3682
UV = 6V
OV = 60V
RSNS
10mΩ
+
R5
10Ω
R6
100Ω
D5
1N4148W
D1
CMZ5945B
68V
∆VSNS
ILIM
VCC HGATE
SHDN
CHG
0.1µF
SOURCE DGATE SENSE
UV
OUT
FB
LTC4364
R7
102k
1%
R8
4.99k
1%
ENOUT
OV
GND
ENABLE
FAULT
FLT
TMR
VOUT
4A
CLAMPED
AT 27V
COUT
22µF
436412 F01
CTMR
47nF
Figure 1. 4A, 12V Overvoltage Output Regulator with Reverse Current Protection
436412f
11
LTC4364-1/LTC4364-2
APPLICATIONS INFORMATION
An overcurrent fault occurs when the current limit circuitry
has been engaged for longer than the timeout delay set
by the timer capacitor. The HGATE pin is then immediately
pulled low by 130mA to the SOURCE pin, turning off the
MOSFET M1. After the fault condition has disappeared
and a cool down period has transpired, the HGATE pin
is allowed to pull back up and turn on the pass device
(LTC4364-2). The LTC4364-1 latches the HGATE pin low
after the overcurrent fault timeout and can be reset using
the SHDN or UV pin (see Resetting Faults).
Input Overvoltage Comparator
Input overvoltage is detected with the OV pin and an external resistive divider connected to the input (Figure 1).
At power-up, if the OV pin voltage is higher than its 1.25V
threshold before the 100μs internal power-on-reset expires,
or before the input undervoltage condition is cleared at
the UV pin, the HGATE pin will be held low until the OV
pin voltage drops below its threshold. To prevent start-up
in the event the board is hot swapped into an overvoltage
supply, separate resistive dividers with filtering capacitors
can be used for the OV and UV pins (Figure 2). The RC
constants should be skewed so that τUV/τOV > 50. In Figure 2, If the board is plugged into a supply that is higher
than 60V, the LTC4364 will not turn on the pass devices
until the supply voltage drops below 60V.
Once the HGATE pin begins pulling high, an input overvoltage condition detected by OV will not turn off the pass
device. Instead, OV prevents the LTC4364 from restarting
following a fault (see Cool Down Period and Restart). This
prevents the pass device from cycling between ON and OFF
states when the input voltage stays at an elevated level for
a long period of time, reducing the stress on the MOSFET.
VIN
383k
475k
UV = 6V
10nF
UV
100k
1nF
OV
10k
The LTC4364 detects input undervoltage conditions such
as low battery using the UV pin. When the voltage at the
UV pin is below its 1.25V threshold, the HGATE pin pulls
low to keep the pass device off. Once the UV pin voltage
rises above the UV threshold plus the UV hysteresis (50mV
typical), the HGATE pin is allowed to pull up without going through a timer cycle. In Figure 1 and Figure 2, the
input UV threshold is set by the resistive dividers to 6V.
An undervoltage condition does not produce an output
at the FLT pin.
Fault Timer
The LTC4364 includes an adjustable fault timer. Connecting a capacitor from the TMR pin to ground sets the
delay period before the MOSFET M1 is turned off during
an overvoltage or overcurrent fault condition. The same
capacitor also sets the cool down period before M1 is
allowed to turn back on after the fault condition has
disappeared. Once a fault condition is detected, a current
source charges up the TMR pin. The current level varies
depending on the voltage drop across the VCC pin and the
OUT pin, corresponding to the MOSFET VDS. The on time
is inversely proportional to the voltage drop across the
MOSFET. This scheme therefore takes better advantage
of the available safe operating area (SOA) of the MOSFET
than would a fixed timer current.
The timer current starts at around 2μA with 0.5V or less
of VCC – VOUT, increasing linearly to 50μA with 75V of
VCC – VOUT during an overvoltage fault (Figure 3a):
ITMR(UP)OV = 2μA + 0.644[μA/V] • (VCC – VOUT – 0.5V)
During an overcurrent fault, the timer current starts at
10μA with 0.5V or less of VCC – VOUT and increases to
260μA with 75V of VCC – VOUT (Figure 3b):
ITMR(UP)OC = 10μA + 3.36[μA/V] • (VCC – VOUT – 0.5V)
LTC4364
0V = 60V
Input Undervoltage Comparator
436412 F02
τUV = (383k||100k) • 10nF
τOV = (475k||10k) •1nF
This arrangement allows the pass device to turn off faster
during an overcurrent event, since more power is dissipated
under this condition. Refer to the Typical Performance
Characteristics section for the timer current at different
VCC – VOUT in both overvoltage and overcurrent events.
Figure 2. External UV and OV Configuration Blocks Start-Up Into
an Overvoltage Condition
436412f
12
LTC4364-1/LTC4364-2
APPLICATIONS INFORMATION
since it would lengthen the overall fault timer period and
cause more stress on the power transistor during an
overcurrent event.
VTMR (V)
ITMR = 5µA
1.35
ITMR = 5µA
1.25
VCC – VOUT = 75V
(ITMR = 50µA)
VCC – VOUT 0
= 75V
Assuming VCC – VOUT remains constant, the on-time of
HGATE during an overvoltage fault is:
VCC – VOUT = 10V
(ITMR = 8µA)
TIME
tFLT
25ms/µF
tWARNING
20ms/µF
tFLT
156ms/µF
=10V
CTMR •1.25V CTMR •100mV
+
ITMR(UP)OV
5µV
and that during an overcurrent fault is:
tWARNING
20ms/µF
(3a) Overvoltage Fault Timer Current
VTMR (V)
tOC =
CTMR •1.35V
ITRM(UP)OC
If the fault condition disappears after TMR reaches 1.25V
but is lower than 1.35V, the TMR pin is discharged by 2μA.
When TMR drops to 0.15V, the FLT pin resets to a high
impedance state.
1.35
1.25
VCC – VOUT = 75V
(ITMR = 260µA)
tOV =
VCC – VOUT = 10V
(ITMR = 42µA)
Cool Down Period and Restart
0
VCC – VOUT
= 75V
=10V
tFLT
4.8ms/µF
TIME
tWARNING
0.38ms/µF
tFLT
29.8ms/µF
tWARNING
2.38ms/µF
436412 F03
(3b) Overcurrent Fault Timer Current
Figure 3. Fault Timer Current of the LTC4364
When the voltage at the TMR pin, VTMR, reaches 1.25V,
the FLT pin pulls low to indicate the detection of a fault
condition and provide warning 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 M1 turning off is given by:
t WARNING =
CTMR • 100mV
5µA
This constant early warning period allows the load to
perform necessary backup or housekeeping functions
before the supply is cut off. After VTMR crosses the 1.35V
threshold, the pass device M1 turns off immediately. Note
that during an overcurrent event, the timer current is not
reduced to 5μA after VTMR has reached 1.25V threshold,
As soon as TMR reaches 1.35V and HGATE pulls low in
a fault condition, the TMR pin starts discharging with a
2μA current. When the TMR pin voltage drops to 0.15V,
TMR charges with 2μA. When TMR reaches 1.35V, it starts
discharging again with 2μA. This pattern repeats 32 times
to form a long cool down timer period before retry (Figure 4). At the end of the cool down period (when the TMR
pin voltage drops to 0.15V the 32nd time), the voltage at
the OV pin is checked. If the OV voltage is above its 1.25V
threshold, retry is inhibited and the HGATE pin remains
low. If the OV pin voltage is below 1.25V minus the OV
hysteresis, the LTC4364-2 retries, pulling the HGATE pin
up and turning on the pass device M1. The FLT pin will
then go to a high impedance state. The total cool down
timer period is given by:
tCOOL =
63 • CTMR • 1.2V
2µA
The latch-off version, LTC4364-1, latches the HGATE and
FLT pins low after a fault timeout. It also generates the
cool down TMR pulses as shown in Figure 4, but does
not retry after the cool down period. There are two ways
to restart the part. The first method is to pull the UV pin
below 0.6V momentarily (>10μs) after the cool down timer
436412f
13
LTC4364-1/LTC4364-2
APPLICATIONS INFORMATION
period. If the UV reset pulse is asserted during the cool
down period, the TMR pulses are unaffected and the part
restarts after the cool down period ends. If OV is higher
than 1.25V while UV reset pulse is applied, the part will
not restart until OV drops below 1.25V even if the cool
down period ends.
reverse input protection with minimum voltage drop in
normal operation. In the event of an input short or a power
supply brownout, reverse current may temporarily flow
through M2. The LTC4364 detects this reverse current
and immediately pulls the DGATE pin to the SOURCE pin,
turning off M2. This minimizes discharge of the output
reservoir capacitor and holds up the output voltage. In
the case where the input supply drops below ground, the
SOURCE pin is pulled below ground through the body
diode of M1. The LTC4364 responds to this condition by
shorting the DGATE pin to the SOURCE pin, keeping M2 off.
The second method of restarting the LTC4364-1 is to
pulse the SHDN pin low for more than 200μs. If this is
applied during the cool down period, the cool down timer
is reset with 1mA quickly discharging the TMR pin, and
the part will restart when TMR drops below 0.15V. If the
SHDN reset pulse is applied after the cool down period,
the part restarts immediately. Sufficient cool down time
should be allowed before toggling the SHDN pin to prevent
overstressing the pass device.
MOSFET Selection
The LTC4364 drives two N-channel MOSFETs, M1 and M2,
as the pass devices to conduct the load current (Figure 1).
The important features are on-resistance, RDS(ON), the
maximum drain-source voltage, V(BR)DSS, the threshold
voltage, and the safe operating area, SOA.
A UV reset pulse has no effect on the operation of the
LTC4364-2. However, if a SHDN reset pulse as described
above is asserted in the middle of the cool down period, the
TMR pin quickly discharges with 1mA and the LTC4364-2
is allowed to restart once TMR drops below 0.15V. The OV
pin gates the restart of either LTC4364-1 or LTC4364-2
with a SHDN reset pulse. The part will not restart until OV
drops below 1.25V.
The maximum drain-source voltage rating must be higher
than the maximum input voltage. If the output is shorted to
ground or in an overvoltage event, the full supply voltage
will appear across M1. If the input is shorted to ground,
M2 will be stressed by the voltage held up at the output.
The gate drive for both MOSFETs is guaranteed to be more
than 10V and less than 16V for those applications with VCC
higher than 8V. This allows the use of standard threshold
voltage N-channel MOSFETs. For systems with VCC less
than 8V, a logic-level MOSFET is required since the gate
drive can be as low as 5V. For supplies of 24V or higher, a
15V Zener diode is recommended to be placed between
Reverse Input Protection
The LTC4364 can withstand reverse voltage without damage. The VCC, SHDN, UV, OV, HGATE, SOURCE and DGATE
pins can all withstand up to –40V with respect to GND.
The LTC4364 controls a second N-channel MOSFET (M2)
as an ideal diode to replace an in-line blocking diode for
1.25V
> tr simplifying the above to:
1
2
P 2 t = ILOAD2 ( VPK − VREG ) τ
2
For the transient conditions of VPK = 80V, VIN = 12V, VREG
= 16V, tr = 10μs and τ = 1ms, and a load current of 3A,
P2t is 18.4W2s—easily handled by a MOSFET in a D-pak
package. The P2t of other transient waveshapes is evaluated by integrating the square of MOSFET power versus
time. LTSpice™ can be used to simulate timer behavior
for more complex transients and cases where overvoltage
and overcurrent faults coexist.
SOA stress of M1 must also be calculated for output shortcircuit conditions. Short-circuit P2t is given by:
2
∆V
P t = VIN • SNS • tOC
R
2
SNS
where ∆VSNS is the overcurrent fault threshold and tOC is
the overcurrent timer interval.
For VIN = 15V, OUT = 0V, ∆VSNS = 25mV, RSNS = 12mΩ
and CTMR = 100nF, P2t is 2.2W2s—less than the transient
SOA calculated in the previous example. Nevertheless,
to account for circuit tolerances this figure should be
doubled to 4.4W2s.
Limiting Inrush Current and HGATE Pin Compensation
The LTC4364 limits the inrush current to any load capacitance by controlling the HGATE pin voltage slew rate. An
external capacitor, CHG, can be connected from HGATE
to ground to slow down the inrush current further at the
expense of slower turn-off time. The gate capacitor is set at:
CHG =
IHGATE(UP)
IINRUSH
The added gate capacitor slows down the turn-off time
during fault conditions and allows higher peak currents to
build up during an output short event. If this is a concern,
an extra resistor, R6, in series with CHG can restore the
turn-off time. A diode, D5, should be placed across R6
with the cathode connected to CHG as shown in Figure 1.
In a fast transient input step, D5 provides a bypass path to
CHG for the benefit of holding HGATE low and preventing
self enhancement.
Shutdown
Short-Circuit Stress
where IHGATE(UP) is the HGATE pin pull-up current, IINRUSH
is the desired inrush current, CL is total load capacitance
at the output. In typical applications, a CHG of 6.8nF is
recommended for loop compensation during overvoltage
and overcurrent events. With input voltage steps faster
than 5V/μs, a larger gate capacitor helps prevent self
enhancement of the N-channel MOSFET.
• CL
The LTC4364 can be shut down to a low current mode
by pulling SHDN below 0.5V. The quiescent VCC current
drops to 10μA for both the LTC4364-1 and the LTC4364-2.
The SHDN pin can be pulled up to 100V or below GND by
up to 40V without damage. Leaving the pin open allows
an internal current source to pull it up to about 4V and
turn the part on. The leakage current at the pin should be
limited to no more than 1μA if no pull-up device is used
to help turn it on.
Supply Transient Protection
The LTC4364 is tested to operate to 80V and guaranteed
to be safe from damage between 100V and −40V. Voltage
transients above 100V or below −40V may cause permanent
damage. During a short-circuit condition, the large change
in current flowing through power supply traces coupled
with parasitic inductances from associated wiring can
cause destructive voltage transients in both positive and
negative directions at the VCC, SOURCE, and OUT pins. To
reduce the voltage transients, minimize the power trace
parasitic inductance by using short, wide traces. A small
RC filter (R4 and C1 in Figure 1) at the VCC pin filters high
voltage spikes of short pulse width.
436412f
16
LTC4364-1/LTC4364-2
APPLICATIONS INFORMATION
Another way to limit supply transients above 100V at the
VCC pin is to use a Zener diode and a resistor, D1 and R4,
as shown in Figure 1. D1 clamps voltage spikes at the VCC
pin while R4 limits the current through D1 to a safe level
during the surge. In the negative direction, D1 along with
R4 clamps the VCC pin near GND. The inclusion of R4 in
series with the VCC pin increases the minimum required
supply voltage due to the extra voltage drop across the
resistor, which is determined by the supply current of the
LTC4364 and the leakage current of D1. 2.2k adds about
1V to the minimum operating voltage.
Output Port Protection
For sustained, elevated suppy voltages, the power dissipation of R4 becomes unacceptable. This can be resolved
by using an external NPN transistor (Q1 in Figure 7) as
a buffer. To protect Q1 against supply reversal, block the
collector of Q1 with a series diode or tie it to the cathode
of D3 and D4 in Figure 1.
Design Example
Transient suppressor D3 in Figure 1 clamps the input
voltage to 200V for voltage transients higher than 200V,
to prevent breakdown of M1. It also blocks forward conduction in D4. D4 limits the SOURCE pin voltage to 24V
below GND when the input goes negative. COUT helps
absorb the inductive energy at the output upon a sudden
input short, protecting the OUT and SENSE pins.
VIN
200V
C1
100nF
R4
22k
1/4W
D1
CMZ5945B
68V
In applications where the output is on a connector, as
shown in Figure 14, if the output is plugged into a supply
that is higher than the input, the ideal diode MOSFET, M2,
turns off to open the backfeeding path. In the case where
the output port is plugged into a supply that is below GND,
the SOURCE pin is pulled below GND through the body
diode of M2. The LTC4364 responds to this condition by
shorting the HGATE pin to the SOURCE pin, turning M1
off and shutting down the current path from VIN to VOUT.
As a design example, consider an application with the
following specifications: VIN = 8V to 14V DC with a peak
transient of 200V and decay time constant τ of 1ms, VOUT
≤ 27V, minimum current limit ILIM(MIN) at 4A, low-battery
detection at 6V, input overvoltage level at 60V, and 1ms
of overvoltage early warning (Figure 1).
Selection of CMZ5945B for D1 will limit the voltage at
the VCC pin to less than 71V during the 200V surge. The
minimum required voltage at the VCC pin is 4V when VIN is
at 6V; the maximum supply current for LTC4364 is 750μA.
The maximum value for R4 to ensure proper operation is:
Q1
PZTA42
VCC
LTC4364
R4 =
6V – 4V
= 2.7k
0.75mA
Select 2.2k for R4 to accommodate all conditions.
With the minimum Zener voltage at 64V, the peak current
through R4 into D1 is then calculated as:
GND
436412 F07
Figure 7. Buffering VCC to Extend Input Supply Range
Output Bypassing
The OUT and SENSE pins can withstand up to 100V above
and 20V below GND. In all applications the output must
be bypassed with at least 22μF low ESR electrolytic (COUT
in Figure 1) to stabilize the voltage and current limiting
loops, and to minimize capacitive feedthrough of input
transients. Total ceramic bypassing of up to one-tenth
the total electrolytic capacitance is permissible without
compromising performance.
ID1(PK) =
200V – 64V
= 62mA
2.2k
which can be handled by the CMZ5945B with a peak power
rating of 200W at 10/1000μs.
With a bypass capacitance of 0.1μF (C1), along with R4
of 2.2k, high voltage transients up to 250V with a pulse
width less than 20μs are filtered out at the VCC pin.
Next, calculate the resistive divider value to limit VOUT to
27V during an overvoltage event:
VREG =
1.25V • (R7 +R8 )
= 27V
R8
436412f
17
LTC4364-1/LTC4364-2
APPLICATIONS INFORMATION
Choosing 250μA for the resistive divider:
R8 =
1.25V
= 5k
250µA
P=
(27V – 1.25V ) •R8 = 102.8k
1.25V
The closest standard value for R7 is 102k.
Now, calculate the sense resistor, RSNS, value:
RSNS =
∆VSNS(MIN)
ILIM
=
45mV
= 11mΩ
4A
Choose 10mΩ for RSNS.
CTMR is then chosen for 1ms of early warning time:
1ms• 5µA
CTMR =
= 50nF
100mV
The closest standard value for CTMR is 47nF.
Finally, calculate R1, R2 and R3 for 6V low battery detection and 60V input overvoltage level:
1.25V
6V
=
R1+R2 +R3 R2 +R3
Simplify the equations and choose 10k for R3 to get:
60V
R2 =
– 1 •R3 = 9 •R3 = 90k
6V
6V
– 1 • (R2+R3) = 3.8 • (R1+R2) = 380k
R1=
1.25V
Select 90.9kΩ for R2 and 383kΩ for R1.
The pass device, M1, should be chosen to withstand an
output short condition with VCC = 14V. In the case of a
severe output short where VOUT = 0V, ITMR(UP) = 55μA and
the total overcurrent fault time is:
18
CTMR • VTMR(G)
ITRM(UP)
RSNS
=
47nF • 1.35V
= 1.15ms
55µA
=
14V • 32mV
= 45W
10mΩ
The corresponding P2t is 2.3W2s.
During an output overload or soft short, the voltage at the
OUT pin could stay at 2V or higher. The total overcurrent
fault time when VOUT = 2V is:
tOC =
47nF •1.35V
= 1.3ms
49µA
The maximum power dissipation in M1 is:
P=
(14V – 2V ) • 55mV = 66W
10mΩ
The corresponding P2t is 5.7W2s. Both of the above conditions are well within the safe operating area of FDB33N25.
To select the pass device, M2, first calculate RDS(ON) to
achieve the desired forward drop VFW at maximum load
current (5.5A). If VFW = 0.25V:
1.25V
60V
=
R1+R2 +R3
R3
tOC =
∆VDS(M1) • ∆VSNS(MAX)
Select 4.99k for R8.
R7 =
The maximum power dissipation in M1 is:
RDS(ON) ≤
VFW
ILOAD(MAX)
=
0.25V
= 45.5mΩ
5.5A
The FDB3682 offers a maximum RDS(ON) of 36mΩ at
VGS = 10V so is a good fit. Its minimum BVDSS of 100V
is also sufficient to handle VOUT transients up to 100V
during an input short-circuit event.
Layout Considerations
To achieve accurate current sensing, use Kelvin connections
to the current sense resistor, RSNS. Limit the resistance
from the SOURCE pin to the sources of the MOSFETs to
below 10Ω. The minimum trace width for 1oz copper foil
is 0.02" per amp to ensure the trace stays at a reasonable temperature. Note that 1oz copper exhibits a sheet
resistance of about 530μΩ/square. Small resistances can
cause large errors in high current applications. Noise immunity will be improved significantly by locating resistive
dividers close to the pins with short VCC and GND traces.
436412f
LTC4364-1/LTC4364-2
TYPICAL APPLICATIONS
+
OV
36V
HGATE
VCC
SHDN
R1
118k
SOURCE DGATE SENSE
UV
R2
44.2k
VOUT
2A
OUT
FB
LTC4364
ENOUT
OV
R3
5.9k
CLOAD
100µF
R5
10Ω D6
DDZ9702T
CHG
47nF
D1
SMAT70A
UV
4.2V
RSNS
20mΩ
M1
SUD50N03-9
VIN
5V TO 28V
GND
FLT
TMR
436412 F08
CTMR
0.22µF
Figure 8. 2A Wide Range Hot Swap Controller with Circuit Breaker
M1
FDB3632
VIN
18V TO 33V
OV
45V
VOUT
2.5A
CLAMPED
CLOAD AT 36V
100µF
+
CHG
47nF
UV
15V
RSNS
15mΩ
M2
FDMS86101
R1
100k
R2
6.04k
R3
3.01k
VCC
SHDN
R5
10Ω
D7
DDZ9702T
D6
DDZ9702T
HGATE
SOURCE
UV
DGATE SENSE
R7
110k
OUT
FB
R8
4.02k
LTC4364
ENOUT
OV
GND
FLT
TMR
436412 F09
CTMR
0.1µF
Figure 9. 28V Hot Swap with Overvoltage Output Regulation at 27V, Circuit Breaker, and Reverse Current Protection
M1
FDB33N25
VIN
36V TO 72V
UV
36V
OV
76V
R2
3.92k
RSNS
10mΩ
+
R4
2.2k CHG
47nF
D1
CMZ5945B
68V
R1
205k
M2
FDB3632
VCC
SHDN
R5
10Ω
D6
DDZ9702T
HGATE
UV
D7
DDZ9702T
SOURCE
DGATE SENSE
OUT
FB
LTC4364
R7
226k
R8
4.02k
ENOUT
OV
R3
3.48k
VOUT
4A
CLAMPED
CLOAD AT 72V
330µF
GND
FLT
TMR
436412 F10
CTMR
0.1µF
Figure 10. 48V Hot Swap with Overvoltage Output Regulation at 72V, Circuit Breaker, and Reverse Current Protection
436412f
19
LTC4364-1/LTC4364-2
TYPICAL APPLICATIONS
M1A
FDD16AN08A0
VINA
12V
M2A
FDD16AN08A0
RSNSA
10mΩ
+
CHGA
6.8nF
HGATE SOURCE DGATE SENSE
VCC
SHDN
UV
R8A
4.99k
ENOUT
TMR
FLT
GND
M1B
FDD16AN08A0
VINB
12V
VCC
M2B
FDD16AN08A0
RSNSB
10mΩ
+
CHGB
6.8nF
COUTB
22µF
R5B
10Ω
HGATE SOURCE DGATE SENSE
SHDN
UV
OUT
FB
LTC4364
OV
R7B
59k
R8B
4.99k
ENOUT
TMR
CTMRB
0.22µF
R7A
59k
OUT
FB
LTC4364
OV
CTMRA
0.22µF
COUTA
22µF
R5A
10Ω
VOUT
CLAMPED
AT 16V
FLT
GND
436412 F11
Figure 11. Redundant Supply Diode-OR with Overvoltage Surge Protection
M1
FDB3632
VIN
12V
M2
FDMS86101
VOUT
CLOAD
100k
SHDN
SHDN
M3
VN2222
VCC
HGATE SOURCE DGATE SENSE OUT
FB
UV
LTC4364
ENOUT
OV
TMR
GND
FLT
436412 F12
Figure 12. High Side Switch with Ideal Diode for Load Protection
436412f
20
LTC4364-1/LTC4364-2
TYPICAL APPLICATIONS
R9
1k, 1W
M1
FDD16AN08A0
VIN
12V
UV
6V
OV
30V
VCC
SHDN
R1
191k
+
R4
2.2k CHG
6.8nF
D1
CMZ5945B
68V
R5
10Ω
HGATE SOURCE DGATE SENSE
UV
R2
40.2k
RSNS
M2
FDD16AN08A0 10mΩ
VOUT
4A
CLAMPED
D8
1N4746A AT 16V
18V, 1W
COUT
22µF
R7
287k
OUT
FB
R8
24.9k
LTC4364
ENOUT
OV
R3
10k
GND
FLT
TMR
436412 F13
CTMR
0.1µF
Figure 13. Overvoltage Regulator with Output Keep Alive During Shutdown
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DE Package
14-Lead Plastic DFN (4mm × 3mm)
(Reference LTC DWG # 05-08-1708 Rev B)
4.00 ±0.10
(2 SIDES)
R = 0.05
TYP
0.70 ±0.05
3.60 ±0.05
2.20 ±0.05
3.30 ±0.05
PACKAGE
OUTLINE
PIN 1
TOP MARK
(SEE NOTE 6)
1.70 ± 0.05
0.25 ± 0.05
0.50 BSC
0.200 REF
3.00 ±0.10
(2 SIDES)
0.75 ±0.05
8
0.40 ± 0.10
14
3.30 ±0.10
1.70 ± 0.10
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
(DE14) DFN 0806 REV B
7
1
0.25 ± 0.05
0.50 BSC
3.00 REF
3.00 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
R = 0.115
TYP
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WGED-3) IN JEDEC
PACKAGE OUTLINE MO-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
436412f
21
LTC4364-1/LTC4364-2
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MS Package
16-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1669 Rev Ø)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
4.039 ± 0.102
(.159 ± .004)
(NOTE 3)
0.50
(.0197)
BSC
0.305 ± 0.038
(.0120 ± .0015)
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
DETAIL “A”
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
0° – 6° TYP
0.280 ± 0.076
(.011 ± .003)
REF
16151413121110 9
GAUGE PLANE
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
0.18
(.007)
SEATING
PLANE
1.10
(.043)
MAX
0.17 – 0.27
(.007 – .011)
TYP
1234567 8
0.50
(.0197)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.86
(.034)
REF
0.1016 ± 0.0508
(.004 ± .002)
MSOP (MS16) 1107 REV Ø
436412f
22
LTC4364-1/LTC4364-2
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
S Package
16-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610 Rev G)
.386 – .394
(9.804 – 10.008)
NOTE 3
.045 ±.005
.050 BSC
16
N
14
13
12
11
10
9
N
.245
MIN
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
1
.030 ±.005
TYP
15
2
3
N/2
N/2
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
× 45°
(0.254 – 0.508)
.008 – .010
(0.203 – 0.254)
1
2
3
4
5
6
.053 – .069
(1.346 – 1.752)
NOTE:
1. DIMENSIONS IN
.014 – .019
(0.355 – 0.483)
TYP
8
.004 – .010
(0.101 – 0.254)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
7
.050
(1.270)
BSC
S16 REV G 0212
INCHES
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
436412f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC4364-1/LTC4364-2
TYPICAL APPLICATION
M1
FDB3632
VIN
12V
CIN
10µF
UV
6V
OV
60V
R1
383k
1%
R2
90.9k
1%
R3
10k
1%
CHG
6.8nF
VCC
SHDN
M2
FDMS86101
RSNS
0.2Ω
R7
49.9k
1%
R5
10Ω
HGATE SOURCE DGATE SENSE
UV
OUT
FB
LTC4364
R9
16.9k
1%
10µF
50V
CER
D2
DDZ9702T
15V
10µF
50V
CER
VOUT*
CLAMPED
AT 18V
RESR
100mΩ
R8
4.99k
1%
ENOUT
OV
GND
FLT
TMR
0.1µF
436412 F14
*PROTECTED AGAINST BACKFEEDING
OR FORWARD CONDUCTING
FROM –20V TO 50V
Figure 14. 0.25A, 12V Surge Stopper with Output Port Protection
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT 4356-1/LT4356-2 Surge Stopper
LT4356-3
LT4356-1: 7A Shutdown Mode
LT4356-2: Auxiliary Amplifier Alive in Shutdown Mode
LT4356-3: Fault Latchoff
LTC4363
High Voltage Surge Stopper
4V to 80V, VCC Clamp, Adjustable Output Voltage Clamp, 60V Reverse
Input Protection, Overcurrent Protection
LTC4366
Floating Surge Stopper
9V to >500V Operation, Adjustable Output Voltage Clamp
LTC4357
Positive High Voltage Ideal Diode Controller
0.5µs Turn-Off Time, 9V to 80V
LTC4359
Ideal Diode Controller with Reverse Input Protection
4V to 80V Operation, –40V Reverse-Input Protection, Low 13µA
Shutdown Current
LTC4352
Ideal MOSFET ORing Diode
External N-Channel MOSFETs Replace ORing Diodes, 0V to 18V
LTC4354
Negative Voltage Diode-OR Controller
Controls Two N-Channel MOSFETs, 1µs Turn-Off, 80V Operation
LTC4355
Positive Voltage Diode-OR Controller
Controls Two N-Channel MOSFETs, 0.5µs Turn-Off, 80V Operation
LTC4365
Window Passer - OV, UV and Reverse Supply Protection
Controller
2.5V to 34V Operation, Protects 60V to –40V
®
436412f
24 Linear Technology Corporation
LT 0712 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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