LTC4358
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FEATURES
APPLICATIONS
DESCRIPTION
5A Ideal Diode
The LTC
®
4358 is a 5A ideal diode that uses an internal
20mΩ N-channel MOSFET to replace a Schottky diode
when used in diode-OR and high current diode applica-
tions. The LTC4358 reduces power consumption, heat
dissipation, and PC board area.
The LTC4358 easily ORs power supplies together to in-
crease total system reliability. In diode-OR applications,
the LTC4358 regulates the forward voltage drop across
the internal MOSFET to ensure smooth current transfer
from one path to the other without oscillation. If the power
source fails or is shorted, a fast turnoff minimizes reverse
current transients.
12V, 5A Diode-OR
n Replaces a Power Schottky Diode
n Internal 20mΩ N-Channel MOSFET
n 0.5μs Turn-Off Time Limits Peak Fault Current
n Operating Voltage Range: 9V to 26.5V
n Smooth Switchover without Oscillation
n No Reverse DC Current
n Available in 14-Pin (4mm × 3mm) DFN and
16-Lead TSSOP Packages
n N+1 Redundant Power Supplies
n High Availability Systems
n Telecom Infrastructure
n Automotive Systems
Power Dissipation vs Load Current
4358 TA01
LTC4358
GND
IN DRAIN
VDD
OUT
VINA = 12V
VOUT TO
5A LOAD
LTC4358
GND
IN DRAIN
VDD
OUT
VINB = 12V
CURRENT (A)
0
0
POWER DISSIPATION (W)
0.5
1.0
1.5
2.0
2.5
3.0
24 6 8
4358 TA01b
DIODE (B530C)
POWER SAVED
FET (LTC4358)
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
LTC4358
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ABSOLUTE MAXIMUM RATINGS
Supply Voltages
IN, OUT, VDD, DRAIN Voltage ................. –0.3V to 28V
Output Voltage
GATE (Note 3) .......................... VIN – 0.2V to VIN + 6V
Operating Ambient Temperature Range
LTC4358C ................................................ 0°C to 70°C
LTC4358I.............................................. –40°C to 85°C
(Notes 1, 2)
1
2
3
4
5
6
7
14
13
12
11
10
9
8
IN
IN
IN
IN
NC
OUT
VDD
IN
IN
IN
IN
GATE
NC
GND
TOP VIEW
15
DRAIN
DE PACKAGE
14-LEAD (4mm s 3mm) PLASTIC DFN
TJMAX = 125°C, θJC = 4°C/W, θJA = 43°C/W
FE PACKAGE
16-LEAD PLASTIC TSSOP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
IN
IN
IN
IN
NC
GATE
NC
GND
IN
IN
IN
IN
IN
NC
OUT
VDD
17
DRAIN
TJMAX = 125°C, θJC = 10°C/W, θJA = 38°C/W
Storage Temperature Range ...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
FE Package ....................................................... 300°C
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC4358CDE#PBF LTC4358CDE#TRPBF 4358 14-Lead (4mm × 3mm) Plastic DFN 0°C to 70°C
LTC4358IDE#PBF LTC4358IDE#TRPBF 4358 14-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C
LTC4358CFE#PBF LTC4358CFE#TRPBF 4358FE 16-Lead Plastic TSSOP 0°C to 70°C
LTC4358IFE#PBF LTC4358IFE#TRPBF 4358FE 16-Lead Plastic TSSOP –40°C to 85°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *Temperature grades are identifi ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/
ORDER INFORMATION
PIN CONFIGURATION
LTC4358
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ELECTRICAL CHARACTERISTICS
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.
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TA = 25°C. VOUT = VDD, VDD = 9V to 26.5V, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VDD Operating Supply Range l926.5V
IDD Operating Supply Current l0.6 mA
IIN IN Pin Current VIN = VOUT ± 1V, No Load l150 350 450 μA
IOUT OUT Pin Current VIN = VOUT ± 1V, No Load l80 160 μA
IDRAIN DRAIN Pin Current VIN = 0V, VOUT = VDD = VDRAIN = 26.5V
l
5
150
μA
μA
ΔVGATE N-Channel Gate Drive (VGATE – VIN)V
DD, VOUT = 9V to 26.5V l4.5 15 V
IGATE(UP) N-Channel Gate Pull Up Current VGATE = VIN, VIN – VOUT = 0.1V l–14 –20 –26 μA
IGATE(DOWN) N-Channel Gate Pull Down
Current in Fault Condition
VGATE = VIN + 5V l12 A
tON Turn-On Time VIN – VOUT = –1V –|
– 0.1V, VDRAIN = VIN,
VOUT = VDD, VGATE – VIN > 4.5V
l200 500 μs
tOFF Turn-Off Time VIN – VOUT = 55mV –|
– –1V, VDRAIN = VIN,
VOUT = VDD, VGATE – VIN < 1V
l300 500 ns
ΔVSD Source-Drain Regulation Voltage
(VIN – VOUT)
1mA < IIN < 100mA l10 25 55 mV
ΔVSD Body Diode Forward Voltage Drop IIN = 5A, MOSFET Off l0.6 0.8 1 V
RDS(ON) Internal N-Channel MOSFET On
Resistance
IIN = 5A l20 40 mΩ
Note 2: All currents into pins are positive, all voltages are referenced to
GND unless otherwise specifi ed.
Note 3: An internal clamp limits the GATE pin to a minimum of 6V above
IN. Driving this pin to voltages beyond this clamp may damage the device.
LTC4358
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TYPICAL PERFORMANCE CHARACTERISTICS
VOUT (V)
0
IOUT (μA)
80
100
4358 G03
60
40
20
010 20 30
VIN = VOUT = VDD
TEMPERATURE (˚C)
-50
RDS(ON) (mΩ)
20
25
30
4358 G04
15
10
5
0-25 0 25 7550 125100
VOUT = VDD = 9V
IIN = 5A
VOUT = VDD = 26.5V
0
tPD (ns)
300
400
4358 G05
200
100
00.2 0.6 0.80.4 1
VIN = 12V
$VSD = VINITIAL -1V
VINITIAL (V) VFINAL (V)
0
tPD (ns)
1500
2000
4358 G06
1000
500
0-0.2 -0.6 -0.8-0.4 -1
VIN = 12V
$VSD = 55mV VFINAL
VDD Current (IDD vs VDD) IN Current (IIN vs VIN) OUT Current (IOUT vs VOUT)
MOSFET RDS(ON) vs Temperature
FET Turn-Off Time
vs Initial Overdrive
FET Turn-Off Time
vs Final Overdrive
VDD (V)
0
IDD (μA)
300
400
4358 G01
200
100
010 20 30
500 VIN = VOUT = VDD
VIN (V)
0
IIN (μA)
300
400
4358 G02
200
100
010 20 30
VIN = VOUT = VDD
LTC4358
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PIN FUNCTIONS
DRAIN: The exposed pad is the drain of the internal
N-channel MOSFET. This pin must be connected to OUT
(Pin 9/Pin 10).
GATE: Gate Drive Output. If reverse current fl ows, a fast
pulldown circuit quickly connects the GATE pin to the IN
pin, turning off the MOSFET. Leave open if unused.
GND: Device Ground.
IN: Input Voltage and Fast Pulldown Return. IN is the
anode of the ideal diode. The voltage sensed at this pin is
used to control the source-drain voltage drop across the
internal MOSFET. If reverse current starts to fl ow, a fast
pulldown circuit quickly turns off the internal MOSFET. The
fast pulldown current is returned through this pin.
NC: No Connection. Not internally connected.
OUT: Output Voltage. The OUT pin is the cathode of the ideal
diode and the common output when multiple LTC4358s
are confi gured as an ideal diode-OR. The voltage sensed
at this pin is used to control the source-drain voltage drop
across the MOSFET. Connect this pin to the drain of the
internal N-channel MOSFET (Pin 15/Pin 17).
VDD: Positive Supply Input. The LTC4358 is powered from
the VDD pin. Connect this pin to OUT either directly or
through an RC hold-up circuit.
(DE/FE PACKAGES)
4358 BD
CHARGE PUMP
–
+
–
+
+
–
FPD
COMP
GATE
AMP
25mV25mV
IN
OUT
DRAIN GATE
GND
IN
VDD
+
–
BLOCK DIAGRAM
LTC4358
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OPERATION
High availability systems often employ parallel-connected
power supplies or battery feeds to achieve redundancy
and enhance system reliability. ORing diodes have been
a popular means of connecting these supplies at the point
of load. The disadvantage of this approach is the forward
voltage drop and resulting effi ciency loss. This drop reduces
the available supply voltage and dissipates signifi cant
power. Using an N-channel MOSFET to replace a Schottky
diode reduces the power dissipation and eliminates the
need for costly heat sinks or large thermal layouts in high
power applications.
The LTC4358 is a single positive voltage ideal diode con-
troller that drives an internal N-channel MOSFET as a pass
transistor to replace a Schottky diode. The IN and DRAIN
pins form the anode and cathode of the ideal diode. The
input supply is connected to the IN pins, while the DRAIN
pin serves as the output. The OUT pin is connected directly
to DRAIN and VDD. VDD is the supply for the LTC4358 and
is derived from the output either directly or through an
RC hold-up circuit.
At power-up, the load current initially fl ows through the
body diode of the internal MOSFET. The internal MOSFET
turns on and the amplifi er tries to regulate the voltage
drop across the IN and OUT connections to 25mV. If
the load current causes more than 25mV of drop, the
MOSFET is driven fully on and the voltage drop is equal to
RDS(ON) • ILOAD.
If the load current is reduced causing the forward drop to
fall below 25mV, the internal MOSFET is driven lower by
a weak pull-down in an attempt to maintain the drop at
25mV. If the load current reverses the MOSFET is turned
off with a strong pull-down.
In the event of a power supply failure, such as if the sup-
ply that is conducting most or all of the current is shorted
to ground, reverse current temporarily fl ows through the
LTC4358 ideal diode that is on. This current is sourced
from any load capacitance and from the other supplies.
The ideal diode is turned off within 500ns, preventing
reverse current from slewing up to a damaging level and
minimizing any disturbance on the output.
LTC4358
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APPLICATIONS INFORMATION
ORing Two Supply Outputs
Where LTC4358s are used to combine the outputs of two
supplies, the power supply with the highest output voltage
sources most or all of the current. If this supply’s output
is quickly shorted to ground while delivering load current,
the current temporarily reverses and fl ows backwards
through the LTC4358. When reverse current fl ows the
LTC4358 ideal diode is quickly turned off.
If the other initially lower supply was not delivering load
current at the time of the fault, the output falls until the
LTC4358 body diode conducts. Meanwhile, the internal
amplifi er turns on the MOSFET until the forward drop is
reduced to 25mV. If instead this supply was delivering
load current at the time of the fault, its ORing MOSFET
was already driven at least partially on, and will be driven
harder in an effort to maintain a drop of 25mV.
Load Sharing
Figure 1 combines the outputs of multiple, redundant
supplies using a simple technique known as droop sharing.
Load current is fi rst taken from the highest output, with the
low outputs contributing as the output voltage falls under
increased loading. The 25mV regulation technique ensures
smooth load sharing between outputs without oscillation.
The degree of sharing depends on the 20mΩ resistance
of the LTC4358 internal MOSFET, the output impedance
of the supplies and their initial output voltages.
LTC4358
GND
IN
PS1
DRAIN
VDD
OUTRTNA
VINA = 12V 12V BUS
LTC4358
GND
IN DRAIN
VDD
OUT
PS2
RTNB
VINB = 12V
PS3
RTNC
VINC = 12V
4358 F01
LTC4358
GND
IN DRAIN
VDD
OUT
Figure 1. Droop Sharing Redundant Supplies
LTC4358
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APPLICATIONS INFORMATION
Figure 3. –12V Reverse Input Protection
LTC4358
GND
IN DRAIN
VDD
OUT
VIN = 12V
CLOAD
C1
0.1μF
R1
100Ω
VOUT
12V
5A
4358 F03
MMBD1205
VDD Hold-Up Circuit
In the event of an input short, parasitic inductance between
the input supply of the LTC4358 and the load bypass
capacitor may cause VDD to glitch below its minimum
operating voltage. This causes the turn-off time (tOFF) to
increase. To preserve the fast turn-off time, local output
bypassing of 39μF or more is suffi cient or a 100Ω, 0.1μF
RC hold-up circuit on the VDD pin can be used as shown
in Figure 2a and Figure 2b.
Layout Considerations
The following advice should be considered when laying out
a printed circuit board for the LTC4358: The OUT pin should
Figure 2. Two Methods of Protecting Against Collapse
of VDD From Input Short and Stray Inductance
4358 F02
LTC4358
GND
IN DRAIN
VDD
OUT
VIN = 12V
LTC4358
GND
IN DRAIN
VDD
OUT
VIN = 12V
R1
1007
C1
0.1MF
CBYPASS
39MF
VOUT
VOUT
(a)
(b)
be connected as closely as possible to the EXPOSED PAD
(drain of the MOSFET) for good accuracy. Keep the traces
to the IN and DRAIN wide and short. The PCB traces as-
sociated with the power path through the MOSFET should
have low resistance. See Figure 4.
The DRAIN acts as a heatsink to remove the heat from the
device. For a single layer PCB with the DFN package, use
Figure 5 to determine the PCB area needed for a speci-
fi ed maximum current and ambient temperature. If using
a two sided PCB, the maximum current is increased by
10%. If the FE package is used, the maximum current is
increased by 4%.
LTC4358
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DIODE CURRENT (A)
3.5
AREA (INCH2)
4.5
10
4358 F05
0.1
1
4.0 6.56.0
5.5
5.0
3.0
85oC 70oC 25oC
TA =
50oC
Figure 5. Maximum Diode Current vs PCB Area
APPLICATIONS INFORMATION
VIN
GND
VOUT
Figure 4. DFN Layout Considerations for 1” × 1” Single Sided PCB
LTC4358
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DE Package
14-Lead Plastic DFN (4mm × 3mm)
(Reference LTC DWG # 05-08-1708)
PACKAGE DESCRIPTION
3.00 ±0.10
(2 SIDES)
4.00 ±0.10
(2 SIDES)
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
0.40 ± 0.10
BOTTOM VIEW—EXPOSED PAD
1.70 ± 0.10
0.75 ±0.05
R = 0.115
TYP
R = 0.05
TYP
3.00 REF
1.70 ± 0.05
17
148
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DE14) DFN 0806 REV B
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
3.00 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
2.20 ±0.05
0.70 ±0.05
3.60 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.25 ± 0.05
0.50 BSC
3.30 ±0.05
3.30 ±0.10
0.50 BSC
LTC4358
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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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PACKAGE DESCRIPTION
FE Package
16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BC
FE16 (BC) TSSOP 0204
0.09 – 0.20
(.0035 – .0079)
0° – 8°
0.25
REF
0.50 – 0.75
(.020 – .030)
4.30 – 4.50*
(.169 – .177)
134
5678
10 9
4.90 – 5.10*
(.193 – .201)
16 1514 13 12 11
1.10
(.0433)
MAX
0.05 – 0.15
(.002 – .006)
0.65
(.0256)
BSC
2.94
(.116)
0.195 – 0.30
(.0077 – .0118)
TYP
2
RECOMMENDED SOLDER PAD LAYOUT
0.45 ±0.05
0.65 BSC
4.50 ±0.10
6.60 ±0.10
1.05 ±0.10
2.94
(.116)
3.58
(.141)
3.58
(.141)
MILLIMETERS
(INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
SEE NOTE 4
4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
6.40
(.252)
BSC
LTC4358
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2007
LT 0808 REV A • PRINTED IN USA
TYPICAL APPLICATION
Plug-In Card Input Diode for Supply Hold-Up
PLUG-IN CARD
CONNECTOR 1
BACKPLANE
CONNECTORS
PLUG-IN CARD
CONNECTOR 2
12V VOUT1
CHOLDUP
VOUT2
GND
GND
4358 TA02
LTC4358
GND
IN OUT
VDD
100Ω
0.1μF
LTC4358
GND
IN OUT
VDD
100Ω
0.1μF
HOT SWAP
CONTROLLER
HOT SWAP
CONTROLLER
+
CHOLDUP
+
PART NUMBER DESCRIPTION COMMENTS
LT1640AH/LT1640AL Negative High Voltage Hot Swap™ Controllers
in SO-8
Negative High Voltage Supplies From –10V to –80V
LT1641-1/LT1641-2 Positive High Voltage Hot Swap Controllers Active Current Limiting, Supplies From 9V to 80V
LT4250 –48V Hot Swap Controller Active Current Limiting, Supplies From –20V to –80V
LTC4251/LTC4251-1/
LTC4251-2
–48V Hot Swap Controllers in SOT-23 Fast Active Current Limiting, Supplies From –15V
LTC4252-1/LTC4252-2/
LTC4252-1A/LTC4252-2A
–48V Hot Swap Controllers in MS8/MS10 Fast Active Current Limiting, Supplies From –15V, Drain Accelerated
Response
LTC4253 –48V Hot Swap Controller with Sequencer Fast Active Current Limiting, Supplies From –15V, Drain Accelerated
Response, Sequenced Power Good Outputs
LT4256 Positive 48V Hot Swap Controller with
Open-Circuit Detect
Foldback Current Limiting, Open-Circuit and Overcurrent Fault Output,
Up to 80V Supply
LTC4260 Positive High Voltage Hot Swap Controller With I2C and ADC, Supplies from 8.5V to 80V
LTC4261 Negative High Voltage Hot Swap Controller With I2C and 10-Bit ADC, Adjustable Inrush and Overcurrent Limits
LTC4350 Hot Swappable Load Share Controller Output Voltage: 1.2V to 20V, Equal Load Sharing
LT4351 MOSFET Diode-OR Controller External N-Channel MOSFETs Replace ORing Diodes, 1.2V to 20V
LTC4352 Ideal Diode Controller with Monitor Controls N-Channel MOSFET, 0V to 18V Operation
LTC4354 Negative Voltage Diode-OR Controller
and Monitor
Controls Two N-Channel MOSFETs, 1μs Turn-Off, 80V Operation
LTC4355 Positive Voltage Diode-OR Controller
and Monitor
Controls Two N-Channel MOSFETs, 0.5μs Turn-Off, 80V Operation
LTC4357 Positive High Voltage Ideal Diode Controller Controls Single N-Channel MOSFET, 0.5μs Turn-Off, 80V Operation
LTC4223-1/LTC4223-2 Dual Supply Hot Swap Controller for Advanced
Mezzanine Cards and μTCA
Controls 12V Main and 3.3V Auxiliary Supplies
Hot Swap is a trademark of Linear Technology Corporation.
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