LTC4357
Positive High Voltage
Ideal Diode Controller
Features
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Description
The LTC
®
4357 is a positive high voltage ideal diode control-
ler that drives an external N-channel MOSFET to replace a
Schottky diode. When used in diode-OR and high current
diode applications, the LTC4357 reduces power consump-
tion, heat dissipation, voltage loss and PC board area.
The LTC4357 easily ORs power sources to increase total
system reliability. In diode-OR applications, the LTC4357
controls the forward voltage drop across the MOSFET to
ensure smooth current transfer from one path to the other
without oscillation. If the power source fails or is shorted,
a fast turn-off minimizes reverse current transients.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Reduces Power Dissipation by Replacing a Power
Schottky Diode with an N-Channel MOSFET
0.5µs Turn-Off Time Limits Peak Fault Current
Wide Operating Voltage Range: 9V to 80V
Smooth Switchover without Oscillation
No Reverse DC Current
Available in 6-Lead (2mm
×
3mm) DFN and
8-Lead MSOP Packages
applications
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N + 1 Redundant Power Supplies
High Availability Systems
AdvancedTCA Systems
Telecom Infrastructure
Automotive Systems
typical application
48V, 10A Diode-OR
V
INA
48V
IN
FDB3632
POWER DISSIPATION (W)
6
5
DIODE (MBR10100)
4
3
2
1
FET (FDB3632)
0
IN
GATE
LTC4357
GND
4357 TA01
Power Dissipation vs Load Current
GATE
LTC4357
GND
OUT
V
DD
V
OUT
TO LOAD
POWER
SAVED
V
INB
48V
FDB3632
0
2
OUT
V
DD
4
6
CURRENT (A)
8
10
4357 TA01b
*SEE FIGURES 2 AND 3 FOR ADDITIONAL OPTIONAL COMPONENTS
4357fd
LTC4357
absolute MaxiMuM ratings
(Notes 1, 2)
Supply Voltages
IN ............................................................ –1V to 100V
OUT, V
DD
.............................................. –0.3V to 100V
Output Voltage
GATE (Note 3) ........................ V
IN
– 0.2V to V
IN
+ 10V
Operating Ambient Temperature Range
LTC4357C ................................................ 0°C to 70°C
LTC4357I.............................................. –40°C to 85°C
LTC4357H .......................................... –40°C to 125°C
LTC4357MP ....................................... –55°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MS Package ...................................................... 300°C
pin conFiguration
TOP VIEW
OUT 1
IN 2
GATE 3
7
GND
6 V
DD
5 NC
4 GND
TOP VIEW
IN
NC
NC
GATE
1
2
3
4
8
7
6
5
OUT
V
DD
NC
GND
DCB PACKAGE
6-LEAD (2mm 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 90°C/W
EXPOSED PAD (PIN 7) PCB GND CONNECTION OPTIONAL
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 163°C/W
orDer inForMation
LEAD FREE FINISH
LTC4357CMS8#PBF
LTC4357IMS8#PBF
LTC4357HMS8#PBF
LTC4357MPMS8#PBF
LEAD BASED FINISH
LTC4357MPMS8
LEAD FREE FINISH
TAPE AND REEL (MINI)
LTC4357CDCB#TRMPBF
LTC4357IDCB#TRMPBF
LTC4357HDCB#TRMPBF
TAPE AND REEL
LTC4357CMS8#TRPBF
LTC4357IMS8#TRPBF
LTC4357HMS8#TRPBF
LTC4357MPMS8#TRPBF
TAPE AND REEL
LTC4357MPMS8#TR
PART MARKING*
LTCXD
LTCXD
LTCXD
LTFWZ
PART MARKING*
LTFWZ
PACKAGE DESCRIPTION
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
PACKAGE DESCRIPTION
8-Lead Plastic MSOP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
–55°C to 125°C
TEMPERATURE RANGE
–55°C to 125°C
TAPE AND REEL
LTC4357CDCB#TRPBF
LTC4357IDCB#TRPBF
LTC4357HDCB#TRPBF
PART MARKING*
LCXF
LCXF
LCXF
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on 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/
4357fd
LTC4357
electrical characteristics
SYMBOL
V
DD
I
DD
I
IN
I
OUT
DV
GATE
I
GATE(UP)
I
GATE(DOWN)
t
OFF
DV
SD
PARAMETER
Operating Supply Range
Supply Current
IN Pin Current
OUT Pin Current
External N-Channel Gate Drive
(V
GATE
– V
IN
)
External N-Channel Gate Pull-Down
Current in Fault Condition
Gate Turn-Off Time
Source-Drain Regulation Voltage
(V
IN
– V
OUT
)
V
IN
= V
OUT
±1V
V
IN
= V
OUT
±1V
V
DD
, V
OUT
= 20V to 80V
V
DD
, V
OUT
= 9V to 20V
V
GATE
= V
IN
+ 5V
–
V
IN
– V
OUT
= 55mV |
–
–1V,
V
GATE
– V
IN
< 1V, C
GATE
= 0pF
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
OUT
= V
DD
, V
DD
= 9V to 80V unless otherwise noted.
CONDITIONS
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MIN
9
TYP
0.5
MAX
80
1.25
500
210
15
15
–26
UNITS
V
mA
µA
µA
V
V
µA
A
150
10
4.5
–14
1
350
80
12
6
–20
2
300
External N-Channel Gate Pull-Up Current V
GATE
= V
IN
, V
IN
– V
OUT
= 0.1V
500
55
ns
mV
V
GATE
– V
IN
= 2.5V
10
25
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 pins are positive, all voltages are referenced to
GND unless otherwise specified.
Note 3:
An internal clamp limits the GATE pin to a minimum of 10V above
IN or 100V above GND. Driving this pin to voltages beyond this clamp may
damage the device.
typical perForMance characteristics
V
DD
Current (I
DD
vs V
DD
)
800
V
DD
= V
OUT
= V
IN
± 1V
400
IN Current (I
IN
vs V
IN
)
V
DD
= V
OUT
= V
IN
+ 1V
V
DD
= V
OUT
= V
IN
– 1V
180
150
OUT Current (I
OUT
vs V
OUT
)
600
I
DD
(µA)
300
V
DD
= V
OUT
= V
IN
+ 1V
120
I
OUT
(µA)
I
IN
(µA)
400
200
90
60
200
100
30
V
DD
= V
OUT
= V
IN
– 1V
0
0
20
40
V
DD
(V)
60
80
4357 G01
0
0
20
40
V
IN
(V)
60
80
4357 G02
0
0
20
40
V
OUT
(V)
60
80
4357 G03
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LTC4357
typical perForMance characteristics
25
GATE Current vs Forward Drop
(I
GATE
vs
DV
SD
)
V
GATE
= 2.5V
15
DV
GATE
vs GATE Current
(DV
GATE
vs I
GATE
)
125
V
IN
> 18V
OUT Current (I
OUT
vs V
IN
)
V
OUT
= 12V, V
IN
= V
DD
100
0
I
GATE
(µA)
V
GATE
(V)
10
I
OUT
(µA)
20
25
4357 G05
V
IN
= 12V
V
IN
= 9V
5
75
–25
50
25
–50
–50
0
0
50
V
SD
(mV)
100
150
4357 G04
0
5
10
15
I
GATE
(µA)
0
0
2
4
8
6
V
IN
(V)
10
12
14
4357 G06
500
FET Turn-Off Time
vs GATE Capacitance
V
GATE
< V
IN
+ 1V
V
SD
= 55mV –1V
400
FET Turn-Off Time
vs Initial Overdrive
V
IN
= 48V
V
SD
= V
INITIAL
–1V
400
300
t
OFF
(ns)
t
PD
(ns)
0
20
40
C
GATE
(nF)
4357 G07
300
200
200
100
0
100
60
80
0
0
0.2
0.6
0.4
V
INITIAL
(V)
0.8
1.0
4357 G08
FET Turn-Off Time
vs Final Overdrive
2000
V
IN
= 48V
V
SD
= 55mV V
FINAL
LOAD CURRENT (A)
10
FET Load Current vs
DVSD
V
IN
= 48V WITH FET (FDB3632)
1500
8
6
t
PD
(ns)
1000
4
500
2
0
0
–1
–0.8
–0.4
–0.6
V
FINAL
(V)
–0.2
0
4357 G09
0
25
∆V
SD
(mV)
50
75
4357 G10
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LTC4357
pin Functions
Exposed Pad:
Exposed pad may be left open or connected
to GND.
GATE:
Gate Drive Output. The GATE pin pulls high, enhanc-
ing the N-channel MOSFET when the load current creates
more than 25mV of voltage drop across the MOSFET.
When the load current is small, the gate is actively driven
to maintain 25mV across the MOSFET. If reverse current
develops more than –25mV of voltage drop across the
MOSFET, a fast pull-down circuit quickly connects the
GATE pin to the IN pin, turning off the MOSFET.
GND:
Device Ground.
IN:
Input Voltage and GATE Fast Pull-Down Return. IN is
the anode of the ideal diode and connects to the source
of the N-channel MOSFET. The voltage sensed at this pin
is used to control the source-drain voltage across the
MOSFET. The GATE fast pull-down current is returned
through the IN pin. Connect this pin as close as possible
to the MOSFET source.
NC:
No Connection. Not internally connected.
OUT:
Drain Voltage Sense. OUT is the cathode of the ideal
diode and the common output when multiple LTC4357s
are configured as an ideal diode-OR. It connects to the
drain of the N-channel MOSFET. The voltage sensed at
this pin is used to control the source-drain voltage across
the MOSFET.
V
DD
:
Positive Supply Input. The LTC4357 is powered from
the V
DD
pin. Connect this pin to OUT either directly or
through an RC hold-up circuit.
block DiagraM
IN
17V
GATE
OUT
CHARGE PUMP
V
DD
FPD
COMP
GATE
AMP
+
–
+
–
25mV
25mV
+
–
+
GND
–
IN
4357 BD
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