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 and LTM are registered trademarks 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
n
n
n
n
n
N + 1 Redundant Power Supplies
High Availability Systems
AdvancedTCA Systems
Telecom Infrastructure
Automotive Systems
TYPICAL APPLICATION
48V, 10A Diode-OR
V
INA
48V
FDB3632
Power Dissipation vs Load Current
6
5
POWER DISSIPATION (W)
DIODE (MBR10100)
4
3
2
1
FET (FDB3632)
0
0
2
4
6
CURRENT (A)
8
10
4357 TA01b
IN
GATE
LTC4357
GND
OUT
V
DD
V
OUT
TO LOAD
POWER
SAVED
V
INB
48V
FDB3632
IN
GATE
LTC4357
GND
OUT
V
DD
4357 TA01
4357fb
1
LTC4357
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Supply Voltages
IN, 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
Storage Temperature Range
DCB Package ..................................... –65°C to 150°C
MS Package ....................................... –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
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
= 200°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC4357CDCB#TRMPBF
LTC4357IDCB#TRMPBF
LTC4357CMS8#PBF
LTC4357IMS8#PBF
TAPE AND REEL
LTC4357CDCB#TRPBF
LTC4357IDCB#TRPBF
LTC4357CMS8#TRPBF
LTC4357IMS8#TRPBF
PART MARKING*
LCXF
LCXF
LTCXD
LTCXD
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
8-Lead Plastic MSOP
8-Lead Plastic MSOP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°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/
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.
SYMBOL
V
DD
I
DD
I
IN
I
OUT
ΔV
GATE
PARAMETER
Operating Supply Range
Supply Current
IN Pin Current
OUT Pin Current
External N-Channel Gate Drive
(V
GATE
– V
IN
)
V
IN
= V
OUT
±1V
V
IN
= V
OUT
±1V
V
DD
, V
OUT
= 20V to 80V
V
DD
, V
OUT
= 9V to 20V
CONDITIONS
l
l
l
l
l
ELECTRICAL CHARACTERISTICS
MIN
9
TYP
0.5
MAX
80
1
450
170
15
15
UNITS
V
mA
μA
μA
V
V
150
10
4.5
350
80
12
6
4357fb
2
LTC4357
ELECTRICAL CHARACTERISTICS
SYMBOL
I
GATE(UP)
I
GATE(DOWN)
t
OFF
ΔV
SD
PARAMETER
External N-Channel Gate Pull Down
Current in Fault Condition
Gate Turn-Off Time
Source-Drain Regulation Voltage
(V
IN
– V
OUT
)
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
l
l
l
l
MIN
–14
1
TYP
–20
2
300
MAX
–26
UNITS
μA
A
External N-Channel Gate Pull Up Current V
GATE
= V
IN
, V
IN
– V
OUT
= 0.1V
V
GATE
= V
IN
+ 5V
–
V
IN
– V
OUT
= 55mV |
–
–1V,
V
GATE
– V
IN
< 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.
4357fb
3
LTC4357
TYPICAL PERFORMANCE CHARACTERISTICS
V
DD
Current (I
DD
vs V
DD
)
800
V
DD
= V
IN
= V
OUT
400
IN Current (I
IN
vs V
IN
)
V
DD
= V
IN
= V
OUT
120
OUT Current (I
OUT
vs V
OUT
)
V
DD
= V
IN
= V
OUT
600
I
DD
(μA)
300
I
OUT
(μA)
40
V
IN
(V)
4357 G01
4357 G02
90
400
I
IN
(μA)
200
60
200
100
30
0
0
20
40
V
DD
(V)
60
80
0
0
20
60
80
0
0
20
40
V
OUT
(V)
60
80
4357 G03
GATE Current vs Forward Drop
(I
GATE(UP)
vs
ΔV
SD
)
25
V
GATE
= 2.5V
15
GATE Voltage vs GATE Current
(ΔV
GATE
vs I
GATE
)
500
V
IN
> 18V
FET Turn-Off Time vs GATE
Capacitance
V
GATE
< V
IN
+ 1V
ΔV
SD
= 50mV –1V
400
300
t
OFF
(ns)
0
V
GATE
(V)
I
GATE
(μA)
10
V
IN
= 12V
V
IN
= 9V
5
200
–25
100
–50
–50
0
50
V
SD
(mV)
100
150
4357 G04
0
0
5
10
15
I
GATE
(μA)
20
25
4357 G06
0
0
10
20
30 40
50
C
GATE
(nF)
60
70
80
4357 G07
FET Turn-Off Time vs Initial
Overdrive
400
2000
V
IN
= 48V
ΔV
SD
= V
INITIAL
–1V
1500
FET Turn-Off Time vs Final
Overdrive
V
IN
= 48V
ΔV
SD
= 55mV V
FINAL
300
t
PD
(ns)
200
t
PD
(ns)
1000
100
500
0
0
0
0.2
0.6
0.4
V
INITIAL
(V)
0.8
1.0
4357 G08
–1
–0.8
–0.4
–0.6
V
FINAL
(V)
–0.2
0
4357 G09
4357fb
4
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 pulldown 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 pulldown 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
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