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| LTC4358 5A Ideal Diode FEATURES n n n n n n n DESCRIPTION The LTC(R)4358 is a 5A ideal diode that uses an internal 20m N-channel MOSFET to replace a Schottky diode when used in diode-OR and high current diode applications. The LTC4358 reduces power consumption, heat dissipation, and PC board area. The LTC4358 easily ORs power supplies together to increase 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. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Replaces a Power Schottky Diode Internal 20m N-Channel MOSFET 0.5s Turn-Off Time Limits Peak Fault Current Operating Voltage Range: 9V to 26.5V Smooth Switchover without Oscillation No Reverse DC Current Available in 14-Pin (4mm x 3mm) DFN and 16-Lead TSSOP Packages APPLICATIONS n n n n N+1 Redundant Power Supplies High Availability Systems Telecom Infrastructure Automotive Systems TYPICAL APPLICATION 12V, 5A Diode-OR 3.0 VINA = 12V IN DRAIN POWER DISSIPATION (W) OUT LTC4358 GND VDD VOUT TO 5A LOAD 2.5 DIODE (B530C) 2.0 1.5 POWER SAVED 1.0 0.5 VINB = 12V IN DRAIN 0 OUT LTC4358 GND 4358 TA01 Power Dissipation vs Load Current FET (LTC4358) 0 2 4 CURRENT (A) 6 8 4358 TA01b VDD 4358fa 1 LTC4358 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2) 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 ................................................ 0C to 70C LTC4358I.............................................. -40C to 85C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) FE Package ....................................................... 300C PIN CONFIGURATION TOP VIEW TOP VIEW IN IN IN IN GATE NC GND 1 2 3 4 5 6 7 15 DRAIN 14 IN 13 IN 12 IN 11 IN 10 NC 9 OUT 8 VDD IN IN IN IN NC GATE NC GND DE PACKAGE 14-LEAD (4mm 3mm) PLASTIC DFN TJMAX = 125C, JC = 4C/W, JA = 43C/W 1 2 3 4 5 6 7 8 17 DRAIN 16 IN 15 IN 14 IN 13 IN 12 IN 11 NC 10 OUT 9 VDD FE PACKAGE 16-LEAD PLASTIC TSSOP TJMAX = 125C, JC = 10C/W, JA = 38C/W ORDER INFORMATION LEAD FREE FINISH LTC4358CDE#PBF LTC4358IDE#PBF LTC4358CFE#PBF LTC4358IFE#PBF TAPE AND REEL LTC4358CDE#TRPBF LTC4358IDE#TRPBF LTC4358CFE#TRPBF LTC4358IFE#TRPBF PART MARKING* 4358 4358 4358FE 4358FE PACKAGE DESCRIPTION 14-Lead (4mm x 3mm) Plastic DFN 14-Lead (4mm x 3mm) Plastic DFN 16-Lead Plastic TSSOP 16-Lead Plastic TSSOP TEMPERATURE RANGE 0C to 70C -40C to 85C 0C to 70C -40C to 85C Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are 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/ 4358fa 2 LTC4358 ELECTRICAL CHARACTERISTICS SYMBOL VDD IDD IIN IOUT IDRAIN VGATE IGATE(UP) IGATE(DOWN) tON tOFF VSD VSD RDS(ON) PARAMETER Operating Supply Range Operating Supply Current IN Pin Current OUT Pin Current DRAIN Pin Current N-Channel Gate Drive (VGATE - VIN) N-Channel Gate Pull Up Current N-Channel Gate Pull Down Current in Fault Condition Turn-On Time Turn-Off Time Source-Drain Regulation Voltage (VIN - VOUT) Body Diode Forward Voltage Drop Internal N-Channel MOSFET On Resistance VIN = VOUT 1V, No Load VIN = VOUT 1V, No Load VIN = 0V, VOUT = VDD = VDRAIN = 26.5V VDD, VOUT = 9V to 26.5V VGATE = VIN, VIN - VOUT = 0.1V VGATE = VIN + 5V - VIN - VOUT = -1V -| 0.1V, VDRAIN = VIN, VOUT = VDD, VGATE - VIN > 4.5V - VIN - VOUT = 55mV |- -1V, VDRAIN = VIN, VOUT = VDD, VGATE - VIN < 1V The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VOUT = VDD, VDD = 9V to 26.5V, unless otherwise noted. CONDITIONS l l l l l l l l l l l l l MIN 9 150 TYP MAX 26.5 0.6 UNITS V mA A A A A V A A 350 80 450 160 5 150 4.5 -14 1 -20 2 200 300 10 0.6 25 0.8 20 15 -26 500 500 55 1 40 s ns mV V m 1mA < IIN < 100mA IIN = 5A, MOSFET Off IIN = 5A 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 6V above IN. Driving this pin to voltages beyond this clamp may damage the device. 4358fa 3 LTC4358 TYPICAL PERFORMANCE CHARACTERISTICS VDD Current (IDD vs VDD) 500 VIN = VOUT = VDD 400 300 IOUT (A) 400 IN Current (IIN vs VIN) 100 VIN = VOUT = VDD 80 OUT Current (IOUT vs VOUT) VIN = VOUT = VDD IDD (A) IIN (A) 300 60 200 200 100 100 40 20 0 0 0 10 VDD (V) 4358 G01 20 30 0 10 VIN (V) 20 30 4358 G02 0 0 10 VOUT (V) 20 30 4358 G03 MOSFET RDS(ON) vs Temperature 30 IIN = 5A 25 VOUT = VDD = 9V RDS(ON) (m) 20 15 VOUT = VDD = 26.5V 10 100 5 0 -50 0 tPD (ns) 300 400 FET Turn-Off Time vs Initial Overdrive 2000 FET Turn-Off Time vs Final Overdrive VIN = 12V VSD = 55mV 1500 VFINAL tPD (ns) -1V 200 VIN = 12V VSD = VINITIAL 1000 500 -25 0 25 50 75 100 125 0 0 0.2 0.4 0.6 0.8 1 4358 G05 0 -0.2 -0.4 -0.6 -0.8 -1 4358 G06 TEMPERATURE (C) 4358 G04 VINITIAL (V) VFINAL (V) 4358fa 4 LTC4358 PIN FUNCTIONS (DE/FE PACKAGES) 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 flows, 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 flow, 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 configured 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. BLOCK DIAGRAM DRAIN IN GATE OUT CHARGE PUMP FPD COMP GATE AMP IN 25mV VDD + + - - 25mV + - + - GND 4358 BD 4358fa 5 LTC4358 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. 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 controller 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 flows through the body diode of the internal MOSFET. The internal MOSFET turns on and the amplifier 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 supply that is conducting most or all of the current is shorted to ground, reverse current temporarily flows 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. 4358fa 6 LTC4358 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 flows backwards through the LTC4358. When reverse current flows 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 amplifier 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 first 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 20m resistance of the LTC4358 internal MOSFET, the output impedance of the supplies and their initial output voltages. VINA = 12V PS1 RTNA LTC4358 GND OUT VDD IN DRAIN 12V BUS VINB = 12V PS2 RTNB IN DRAIN OUT LTC4358 GND VDD VINC = 12V PS3 RTNC IN DRAIN OUT LTC4358 GND 4358 F01 VDD Figure 1. Droop Sharing Redundant Supplies 4358fa 7 LTC4358 APPLICATIONS INFORMATION 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 39F or more is sufficient or a 100, 0.1F 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 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 associated 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 specified 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%. (a) VIN = 12V IN DRAIN OUT LTC4358 GND VDD CBYPASS 39 F MMBD1205 LTC4358 VDD GND C1 0.1F VOUT VIN = 12V IN DRAIN OUT R1 100 VOUT 12V 5A CLOAD 4358 F03 (b) VIN = 12V IN DRAIN OUT LTC4358 GND 4358 F02 VOUT R1 100 C1 0.1 F Figure 3. -12V Reverse Input Protection VDD Figure 2. Two Methods of Protecting Against Collapse of VDD From Input Short and Stray Inductance 4358fa 8 LTC4358 APPLICATIONS INFORMATION VIN GND VOUT Figure 4. DFN Layout Considerations for 1" x 1" Single Sided PCB 10 85 C TA = 70 C 50 C 25 C AREA (INCH2) 1 0.1 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 DIODE CURRENT (A) 4358 F05 Figure 5. Maximum Diode Current vs PCB Area 4358fa 9 LTC4358 PACKAGE DESCRIPTION DE Package 14-Lead Plastic DFN (4mm x 3mm) (Reference LTC DWG # 05-08-1708) 0.70 0.05 3.60 0.05 2.20 0.05 3.30 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 R = 0.115 TYP 8 14 0.40 0.10 3.00 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) 3.30 0.10 1.70 0.10 PIN 1 NOTCH R = 0.20 OR 0.35 x 45 CHAMFER (DE14) DFN 0806 REV B 7 0.200 REF 0.75 0.05 3.00 REF 0.00 - 0.05 1 0.25 0.05 0.50 BSC 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 4358fa 10 LTC4358 PACKAGE DESCRIPTION FE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation BC 3.58 (.141) 4.90 - 5.10* (.193 - .201) 3.58 (.141) 16 1514 13 12 1110 9 6.60 0.10 4.50 0.10 SEE NOTE 4 2.94 (.116) 0.45 0.05 1.05 0.10 0.65 BSC 6.40 2.94 (.252) (.116) BSC RECOMMENDED SOLDER PAD LAYOUT 12345678 1.10 (.0433) MAX 0 - 8 4.30 - 4.50* (.169 - .177) 0.25 REF 0.09 - 0.20 (.0035 - .0079) 0.50 - 0.75 (.020 - .030) 0.65 (.0256) BSC NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE 0.195 - 0.30 (.0077 - .0118) TYP 0.05 - 0.15 (.002 - .006) FE16 (BC) TSSOP 0204 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE 4358fa 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. 11 LTC4358 TYPICAL APPLICATION Plug-In Card Input Diode for Supply Hold-Up BACKPLANE PLUG-IN CARD CONNECTORS CONNECTOR 1 12V IN OUT HOT SWAP CONTROLLER 100 VOUT1 LTC4358 GND VDD 0.1F + CHOLDUP GND IN OUT HOT SWAP CONTROLLER 100 VOUT2 LTC4358 GND VDD 0.1F + CHOLDUP GND 4358 TA02 PLUG-IN CARD CONNECTOR 2 RELATED PARTS PART NUMBER LT1640AH/LT1640AL LT1641-1/LT1641-2 LT4250 LTC4251/LTC4251-1/ LTC4251-2 LTC4252-1/LTC4252-2/ LTC4252-1A/LTC4252-2A LTC4253 LT4256 LTC4260 LTC4261 LTC4350 LT4351 LTC4352 LTC4354 LTC4355 LTC4357 LTC4223-1/LTC4223-2 DESCRIPTION Negative High Voltage Hot SwapTM Controllers in SO-8 Positive High Voltage Hot Swap Controllers -48V Hot Swap Controller -48V Hot Swap Controllers in SOT-23 -48V Hot Swap Controllers in MS8/MS10 -48V Hot Swap Controller with Sequencer Positive 48V Hot Swap Controller with Open-Circuit Detect Positive High Voltage Hot Swap Controller Negative High Voltage Hot Swap Controller Hot Swappable Load Share Controller MOSFET Diode-OR Controller Ideal Diode Controller with Monitor Negative Voltage Diode-OR Controller and Monitor Positive Voltage Diode-OR Controller and Monitor Positive High Voltage Ideal Diode Controller COMMENTS Negative High Voltage Supplies From -10V to -80V Active Current Limiting, Supplies From 9V to 80V Active Current Limiting, Supplies From -20V to -80V Fast Active Current Limiting, Supplies From -15V Fast Active Current Limiting, Supplies From -15V, Drain Accelerated Response Fast Active Current Limiting, Supplies From -15V, Drain Accelerated Response, Sequenced Power Good Outputs Foldback Current Limiting, Open-Circuit and Overcurrent Fault Output, Up to 80V Supply With I2C and ADC, Supplies from 8.5V to 80V With I2C and 10-Bit ADC, Adjustable Inrush and Overcurrent Limits Output Voltage: 1.2V to 20V, Equal Load Sharing External N-Channel MOSFETs Replace ORing Diodes, 1.2V to 20V Controls N-Channel MOSFET, 0V to 18V Operation Controls Two N-Channel MOSFETs, 1s Turn-Off, 80V Operation Controls Two N-Channel MOSFETs, 0.5s Turn-Off, 80V Operation Controls Single N-Channel MOSFET, 0.5s Turn-Off, 80V Operation Controls 12V Main and 3.3V Auxiliary Supplies Dual Supply Hot Swap Controller for Advanced Mezzanine Cards and TCA Hot Swap is a trademark of Linear Technology Corporation. 4358fa 12 Linear Technology Corporation (408) 432-1900 LT 0808 REV A * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 FAX: (408) 434-0507 www.linear.com (c) LINEAR TECHNOLOGY CORPORATION 2007 |
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