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LTC4355

4355ff

For more information www.linear.com/LTC4355

Features

applications

Description

Positive High Voltage

Ideal Diode-OR with Input Supply

and Fuse Monitors

The LTC

4355 is a positive voltage ideal diode-OR control-

ler that drives two external N-channel MOSFETs. Forming

the dio

de-OR with N-channel MOSFETs instead of Schottky

diodes reduces power consumption, heat dissipation and

PC board area.

With the LTC4355, power sources can easily be ORed

together to increase total system reliability. The LTC4355

an diode

-OR two positive supplies or the return paths of

two negative supplies, such as in a –48V system.

In the forward direction the LTC4355 controls the volt

age drop across the MOSFET to ensure smooth current

transfe

r from one path to the other without oscillation. If

a power source fails or is shorted, fast turnoff minimizes

reverse current transients.

Power fault detection indicates if the input supplies are

not in regulation, the inline fuses are blown, or the volt-

ages across the MOSFETs are greater than the fault

reshold.

+48V Diode-OR

Replaces Power Schottky Diodes

Controls N-Channel MOSFETs

0.3µs Turn-Off Time Limits Peak Fault Current

Wide Operating Voltage Range: 9V to 80V

Smooth Switchover without Oscillation

No Reverse DC Current

Monitors V

, Fuse, and MOSFET Diode

Available in 14-Lead (4mm × 3mm) DFN,

16-Lead MS and SO Packages

High Availability Systems

AdvancedTCA

(ATCA) Systems

+48V and –48V Distributed Power Systems

Telecom Infrastructure

Power Dissipation vs Load Current

typical application

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.

4355 TA01

LTC4355

GND

GATE1 GATE2IN1 OUTIN2

MON1

MON2

SET

12.7k

340k

12.7k

340k

22k 22k 22k

22k 22k

GREEN LEDs

PANASONIC LN1351C

GND

FDB3632

LOAD

IN1

= +48V

IN2

= +48V

VDSFLT

FUSEFLT1

FUSEFLT2

PWRFLT1

PWRFLT2

CURRENT (A)

POWER DISSIPATION (W)

2 4 6 8

4355 TA02

DIODE (MBR10100)

FET (FDB3632)

POWER

SAVED

Summary of content (20 pages)

PAGE 1
LTC4355 Positive High Voltage Ideal Diode-OR with Input Supply and Fuse Monitors Description Features n n n n n n n n Replaces Power Schottky Diodes Controls N-Channel MOSFETs 0.
PAGE 2
LTC4355 Absolute Maximum Ratings (Notes 1, 2) Supply Voltages IN1, IN2................................................... –1V to 100V OUT...................................................... –0.3V to 100V Input Voltages MON1, MON2, SET................................... –0.3V to 7V Output Voltages GATE1 (Note 3).................... VIN1 – 0.2V to VIN1 + 13V GATE2 (Note 3).................... VIN2 – 0.2V to VIN2 + 13V PWRFLT1, PWRFLT2, VDSFLT, FUSEFLT1, FUSEFLT2................................ –0.
PAGE 3
LTC4355 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. 9V < VOUT < 80V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP VOUT Operating Supply Range l IOUT Supply Current l IINx INx Pin Input Current GATE High l 0.5 DVGATEx External N-Channel Gate Drive (VGATEx – VINx) VOUT = 20V to 80V VOUT = 9V to 20V l l 10 4.
PAGE 4
LTC4355 Typical Performance Characteristics IOUT vs VOUT 1.0 VOUT = VIN 1.0 0.5 0 –20 VIN = VOUT 0.75 IIN (mA) IOUT (mA) 1.5 IIN vs VIN 0.5 0.25 0 40 20 60 0 80 VGATE = 2.5V 20 40 0 40 20 VOUT (V) 60 60 –50 80 0 VIN (V) 50 100 4355 G02 4355 G03 Fault Output Low vs Load Current DVGATE vs IGATE Fault Output Low vs Temperature 0.3 VIN > 18V 150 VSD (mV) 4355 G01 15 IGATE vs DVSD 0 IGATE (µA) 2.0 150 IFLT = 5mA 125 0.
PAGE 5
LTC4355 Pin Functions Exposed Pad: Exposed pad may be left open or connected to GND. FUSEFLTx: Fuse Fault Outputs. Open-drain output that pulls to GND when VINx < 3.5V, indicating that the fuse has blown open. Otherwise, this output is high impedance. Connect to GND if unused. GATEx: Gate Drive Outputs. The GATE pins pull high, enhancing the N-channel MOSFET when the load current creates more than 25mV of voltage drop across the MOSFET.
PAGE 6
LTC4355 Block Diagram IN1 GATE1 OUT GATE2 17V IN2 17V – + 25mV –+ ∆VSD(FLT) 25mV + – ∆VSD(FLT) +– ∆VSD1(FLT) FAULT + – + – – + + GATE2 AMP – GATE1 AMP ∆VSD2(FLT) FAULT ∆VSD(FLT) = 0.25V, 0.5V OR 1.5V VDSFLT – – FUSEFLT1 + FUSEFLT2 FUSE2 FAULT FUSE1 FAULT + – 3.5V 3.5V + – + PWRFLT1 PWRFLT2 + – + – MON1 + – 1.23V – MON2 + MON1 MON2 1.23V 4355 BD GND SET 4355ff 6 For more information www.linear.
PAGE 7
LTC4355 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 efficiency loss. This drop reduces the available supply voltage and dissipates significant power.
PAGE 8
LTC4355 Applications Information MOSFET Selection The LTC4355 drives N-channel MOSFETs to conduct the load current. The important features of the MOSFETs are on-resistance RDS(ON), the maximum drain-source voltage VDSS, and the threshold voltage. The gate drive for the MOSFET is guaranteed to be greater than 4.5V when the supply voltage at VOUT is between 9V and 20V. When the supply voltage at VOUT is greater than 20V, the gate drive is guaranteed to be greater than 10V.
PAGE 9
LTC4355 Applications Information System Power Supply Failure High slew rates coupled with parasitic inductances in series with the input and output paths may cause potentially destructive transients to appear at the IN and OUT pins of the LTC4355 during reverse recovery. A zero impedance short-circuit directly across an input that is supplying current is especially troublesome because it permits the highest possible reverse current to build up during the delay phase.
PAGE 10
LTC4355 Applications Information Loop Stability Next, select the resistive dividers that guarantee the PWRFLT pins will not assert when the input supplies are above 36V. The maximum VMONx(TH) is 1.245V and the maximum IMONx(IN) is 1µA. Choose a 1% tolerance resistor R1 = 12.7k. Then, The servo loop is compensated by the parasitic capacitance of the power N-channel MOSFET. No further compensation components are normally required.
PAGE 11
LTC4355 Applications Information Layout Considerations The following advice should be considered when laying out a printed circuit board for the LTC4355. Keep the traces to the MOSFETs wide and short. The PCB traces associated with the power path through the MOSFETs should have low resistance (see Figure 3). S D D S D D D D D D FET S G FET S S S IN1 LTC4355 GATE1 OUT GATE2 IN2 For the DFN package, pin spacing may be a concern at voltages greater than 30V.
PAGE 12
LTC4355 typical applications –36V to –72V/10A with Positive Supply and Negative Supply Diode-ORing 15A RTNA IRF3710 15A RTNB IRF3710 33k 340k 340k IN1 GATE1 IN2 MON2 12.7k GND 12.7k 33k 33k VDSFLT FUSEFLT1 FUSEFLT2 PWRFLT1 PWRFLT2 LTC4355 SET 33k GATE2 OUT MON1 33k GREEN LEDs PANASONIC LN1351C LOAD 12k 33k VCC LTC4354 DA VA = –48V VB = –48V 10A 10A DB 2k GA FAULT GB VSS 1µF 2k RED LED PANASONIC LN1251CLA IRF3710 IRF3710 4355 F04 4355ff 12 For more information www.linear.
PAGE 13
LTC4355 typical applications –48V/5A with Positive Supply and Negative Supply Diode-ORing with Reverse Input Protection RTNA RTNB 10A FDS3672 10A FDS3672 IN1 GATE1 IN2 GATE2 OUT = BAS21 LTC4355 GND SMBT70A LOAD 12k VCC 1µF LTC4354 DA VA = –48V VB = –48V 7A DB 2k GA GB VSS 2k FDS3672 7A FDS3672 4355 F05 NOTE: MAXIMUM VOLTAGE BETWEEN ANY TWO INPUTS = 80VDC +24V Diode-OR With Reverse Input Protection FDS3672 VIN1 = +24V FDS3672 VIN2 = +24V LOAD = BAS21 IN1 GATE1 IN2 GATE2 OUT LT
PAGE 14
LTC4355 typical applications Single 12V/15A Ideal Diode with Parallel Drivers F1 15A VIN = 12V M1 HAT2165H TO LOAD R1 86.6k R3 10k IN1 IN2 VDSFLT FUSEFLT1 PWRFLT1 FUSEFLT2 PWRFLT2 LTC4355 SET MON2 R5 10k GATE1 GATE2 OUT MON1 R2 12.7k R4 10k GND D1 D2 GND GREEN LEDs D3 PANASONIC LN1351C 4355 TA03 Single 36V to 72V/30A Ideal Diode Using Parallel MOSFETs F1 30A VIN = +48V M1 IRFS4710 TO LOAD M2 IRFS4710 R3 33k R1 340k IN1 SET R2 12.
PAGE 15
LTC4355 TYPICAL Applications AdvancedTCA with High Side and Low Side Ideal Diode-OR and Hot SwapTM Controller with I2C Current and Voltage Monitor LONG 10A LONG 10A FDS3672 VRTN_A –48VRTN(OUT) FDS3672 VRTN_B 91Ω SMBT70A 22nF 100V IN1 GATE1 IN2 GATE2 OUT MON1 SET MON2 D ENABLE_B ENABLE_A SHORT 100k SHORT 100k 1M 1M LTC4355 GND 1.1k D 1.1k FMMT5401 D 100k 1.1k 1.1k FMMT5401 D 100k 1µF 137k 10k 107k VCC LTC4354 100nF 2k 2k MEDIUM LONG 100nF 100nF 100k 10.2k 100nF 2.
PAGE 16
LTC4355 TYPICAL Applications 36V to 72V/10A with Positive Supply and Negative Supply Diode-ORing, Combined Fault Outputs, and Zener Clamps on MOSFET Gates 10A VA = 48V IRLR3110ZPbF 12V ZENER CMZ4699 10A VB = 48V IRLR3110ZPbF 33k 12V ZENER CMZ4699 340k 340k IN1 GATE1 IN2 GATE2 OUT MON1 LTC4355 SET MON2 12.7k VDSFLT FUSEFLT1 FUSEFLT2 PWRFLT1 PWRFLT2 GND GREEN LED PANASONIC LN1351C 12.
PAGE 17
LTC4355 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) 0.70 ±0.05 3.30 ±0.05 3.60 ±0.05 2.20 ±0.05 1.70 ± 0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 3.00 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ±0.10 (2 SIDES) R = 0.05 TYP 3.00 ±0.10 (2 SIDES) R = 0.115 TYP 8 0.40 ± 0.10 14 3.30 ±0.
PAGE 18
LTC4355 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 A) 4.039 ±0.102 (.159 ±.004) (NOTE 3) 0.889 ±0.127 (.035 ±.005) 5.10 (.201) MIN 16151413121110 9 3.20 – 3.45 (.126 – .136) 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 GAUGE PLANE 0.53 ±0.152 (.021 ±.006) 0.50 (.
PAGE 19
LTC4355 Revision History (Revision history begins at Rev E) REV DATE DESCRIPTION PAGE NUMBER E 2/10 Updated Features section and removed patent 1 Revised tOFF conditions 3 Revised NC pin description Revised Typical Application drawings F 8/13 5 13, 15, 16 Corrected part number LTC4352 in Related Parts 20 Added H-grade (LTC4355H) information 2 Changed θJA: MS package from 125°C/W to 120°C/W, S package from 75°C/W to 80°C/W 2 Swapped ampere ratings between the two sets of fuses 12 4355f
PAGE 20
LTC4355 Typical Application 200W AdvancedTCA Ideal Diode-OR 10A RTNA FDS3672 10A RTNB FDS3672 IN1 GATE1 IN2 GATE2 OUT LTC4355 GND LOAD 12k VCC 1µF LTC4354 DA 7A VA = –48V DB 2k GA VSS 2k 7A VB = –48V GB FDS3672 FDS3672 4355 TA08 Related Parts PART NUMBER DESCRIPTION COMMENTS LTC1921 Dual –48V Supply and Fuse Monitor UV/OV Monitor, –10V to –80V Operation, MSOP Package LT4250 –48V Hot Swap Controller Active Current Limiting, Supplies From –20V to –80V LTC4251/LTC4251-1/ LTC4251