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 0.3µs Turn-Off Time Limits Peak Fault Current Wide Operating Voltage Range: 9V to 80V Smooth Switchover without Oscillation No Reverse DC Current Monitors VIN, Fuse, and MOSFET Diode Available in 14-Lead (4mm × 3mm) DFN, 16-Lead MS and SO Packages The LTC®4355 is a positive voltage ideal diode-OR controller that drives two external N-channel MOSFETs. Forming the diode-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 can 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 voltage drop across the MOSFET to ensure smooth current transfer from one path to the other without oscillation. If a power source fails or is shorted, fast turnoff minimizes reverse current transients. Applications High Availability Systems AdvancedTCA® (ATCA) Systems n +48V and –48V Distributed Power Systems n Telecom Infrastructure n n Power fault detection indicates if the input supplies are not in regulation, the inline fuses are blown, or the voltages across the MOSFETs are greater than the fault threshold. 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. Typical Application +48V Diode-OR FDB3632 7A VIN2 = +48V FDB3632 22k 340k 340k IN1 GATE1 IN2 GATE2 OUT MON1 SET MON2 12.7k GND 12.7k 6 TO LOAD LTC4355 GND 22k 22k 22k 22k VDSFLT FUSEFLT1 FUSEFLT2 PWRFLT1 PWRFLT2 5 POWER DISSIPATION (W) 7A VIN1 = +48V Power Dissipation vs Load Current DIODE (MBR10100) 4 3 POWER SAVED 2 1 FET (FDB3632) 0 GREEN LEDs PANASONIC LN1351C 4355 TA01 0 2 4 6 CURRENT (A) 8 10 4355 TA02 4355ff For more information www.linear.com/LTC4355 1 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................................ –0.3V to 8V Operating Ambient Temperature Range LTC4355C................................................. 0°C to 70°C LTC4355I..............................................–40°C to 85°C LTC4355H...........................................–40°C to 125°C Storage Temperature Range....................–65°C to 150°C Lead Temperature (Soldering, 10 sec) MS, SO Packages.............................................. 300°C pin configuration TOP VIEW TOP VIEW IN1 1 14 MON1 GATE1 2 13 PWRFLT1 OUT 3 GATE2 4 IN2 5 10 PWRFLT2 VDSFLT 6 9 MON2 GND 7 8 SET 15 12 FUSEFLT1 11 FUSEFLT2 IN1 1 TOP VIEW 1 2 3 4 5 6 7 8 IN1 GATE1 NC OUT NC GATE2 IN2 VDSFLT 16 15 14 13 12 11 10 9 MON1 PWRFLT1 FUSEFLT1 FUSEFLT2 PWRFLT2 MON2 SET GND MS PACKAGE 16-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 120°C/W DE14 PACKAGE 14-LEAD (4mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 15) PCB GND CONNECTION OPTIONAL 16 MON1 GATE1 2 15 PWRFLT1 NC 3 14 FUSEFLT1 OUT 4 13 FUSEFLT2 NC 5 12 PWRFLT2 GATE2 6 11 MON2 IN2 7 10 SET NC 8 9 GND S PACKAGE 16-LEAD PLASTIC SO TJMAX = 125°C, θJA = 80°C/W order information LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4355CDE#PBF LTC4355CDE#TRPBF 4355 14-Lead (4mm × 3mm) Plastic DFN 0°C to 70°C LTC4355IDE#PBF LTC4355IDE#TRPBF 4355 14-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C LTC4355CS#PBF LTC4355CS#TRPBF LTC4355CS 16-Lead Plastic SO 0°C to 70°C LTC4355IS#PBF LTC4355IS#TRPBF LTC4355IS 16-Lead Plastic SO –40°C to 85°C LTC4355CMS#PBF LTC4355CMS#TRPBF 4355 16-Lead Plastic MSOP 0°C to 70°C LTC4355IMS#PBF LTC4355IMS#TRPBF 4355 16-Lead Plastic MSOP –40°C to 85°C LTC4355HMS#PBF LTC4355HMS#TRPBF 4355 16-Lead Plastic MSOP –40°C to 125°C 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/ 4355ff 2 For more information www.linear.com/LTC4355 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 4.5 IGATEx(UP) External N-Channel Gate Pull-Up Current VGATEx = VINx , VINx – VOUT = 100mV l IGATEx(DN) External N-Channel Gate Pull-Down in Fault Condition Gate Drive Off, VGATEx = VINx +5V l tOFF Gate Turn-Off Time – VINx – VOUT = 55mV |––1V, CGATE = 0 VGATEx – VINx < 1V VMONx(TH) MONx Pin Threshold Voltage VMONx Rising VMONx(HYST) MONx Pin Hysteresis Voltage IMONx(IN) MONx Pin Input Current VMONx = 1.23V l VINx(TH) INx Pin Threshold Voltage VINx Rising l VINx(HYST) INx Pin Hysteresis Voltage DVSD Source-Drain Regulation Voltage (VINx – VOUT ) DVSD(FLT) Short-Circuit Fault Voltage (VINx – VOUT) Rising DVSD(FLT)(HYST) Short-Circuit Fault Hysteresis Voltage VFLT PWRFLTx, FUSEFLTx, VDSFLT Pins Output Low IPWRFLTx, IFUSEFLTx, IVDSFLT = 5mA l 100 200 mV IFLT PWRFLTx, FUSEFLTx, VDSFLT Pins Leakage Current VPWRFLTx, VFUSEFLTx, VVDSFLT = 5V l 0 ±1 µA RSET(L) SET Resistance Range for DVSD(FLT) = 0.25V l 0 5 kW RSET(M) SET Resistance Range for DVSD(FLT) = 0.5V l 50 150 kW RSET(H) SET Resistance Range for DVSD(FLT) = 1.5V l 1 9 MAX UNITS 80 V 2 3 mA 0.6 1.2 mA 14 6 18 18 V V –14 –20 –26 µA 1 2 l A 0.3 0.4 µs l 1.209 1.227 1.245 l 10 30 45 mV 0 ±1 µA 3 3.5 4 V l 25 75 150 mV VGATEx – VINx = 2.5V l 10 25 55 mV SET = 0V SET = 100kΩ SET = Hi-Z l l l 0.2 0.4 1.3 0.25 0.5 1.5 0.3 0.6 1.6 V V V 30 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. V mV MW Note 2: All currents into pins are positive, all voltages are referenced to GND unless otherwise specified. Note 3: The GATEx pins are internally limited to a minimum of 13V above INx. Driving these pins beyond the clamp may damage the part. 4355ff For more information www.linear.com/LTC4355 3 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 0.2 VFLT (V) ∆VGATE (V) VIN = 12V VFLT (mV) 10 VIN = 9V 100 0.1 5 75 0 0 –5 –10 –15 IGATE (µA) –20 0 –25 0 10 5 400 300 300 100 FET Turn-Off Time vs Final Overdrive 2000 VIN = 48V ∆VSD = VINITIAL –1V 200 20 20 CGATE (nF) 40 50 4355 G07 0 1000 500 100 10 VIN = 48V ∆VSD = 50mV VFINAL 1500 tPD (ns) 400 tPD (ns) tOFF (ns) 500 VGATE < VIN + 1V ∆VSD = 50mV –1V 0 4355 G06 FET Turn-Off Time vs Initial Overdrive 200 100 4355 G05 FET Turn-Off Time vs GATE Capacitance 0 50 0 TEMPERATURE (°C) IFLT (mA) 4355 G04 500 50 –50 15 0 0.2 0.6 0.4 VINITIAL (V) 0.8 1.0 4355 G08 0 –1.0 –0.8 –0.4 –0.6 VFINAL (V) –0.2 0 4355 G09 4355ff 4 For more information www.linear.com/LTC4355 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. When the load current is small, the gates are actively driven to maintain 25mV across the MOSFET. If the reverse current develops more than –25mV of voltage drop across a MOSFET, a fast pull-down circuit quickly connects the GATE pin to the IN pin, turning off the MOSFET. Limit the capacitance between the GATE and IN pins to less than 0.1µF. GND: Device Ground. INx: Input Voltages and GATE Fast Pull-Down Returns. The IN pins are the anodes of the ideal diodes and connect to the sources of the N-channel MOSFETs. The voltages sensed at these pins are used to control the source-drain voltages across the MOSFETs and are used by the fault detection circuits that drive the PWRFLT, FUSEFLT, and VDSFLT pins. The GATE fast pull-down current is returned through the IN pins. Connect these pins as close to the MOSFET sources as possible. Connect to OUT if unused. MONx: Input Supply Monitors. These pins are used to sense the input supply voltages. Connect these pins to external resistive dividers between the input supplies and GND. If VMONx falls below 1.23V, the PWRFLTx pin pulls to GND. Connect to GND if unused. NC: No Connection. Not internally connected. These pins provide extra distance between high and low voltage pins. OUT: Drain Voltage Sense and Positive Supply Input. OUT is the diode-OR output of IN1 and IN2. It connects to the common drain connection of the N-channel MOSFETs. The voltage sensed at this pin is used to control the sourcedrain voltages across the MOSFETs and is used by the fault detection circuits that drive the PWRFLT and VDSFLT pins. The LTC4355 is powered from the OUT pin. PWRFLTx: Power Fault Outputs. Open-drain output that pulls to GND when VMONx falls below 1.23V or the forward voltage across the MOSFET exceeds DV SD(FLT). When V MONx is above 1.23V and the forward voltage across the MOSFET is less than DVSD(FLT), PWRFLTx is high impedance. Connect to GND if unused. SET: DVSD(FLT) Threshold Configuration Input. Tying SET to GND, to a 100k resistor connected to GND, or leaving SET open configures the DVSD(FLT) forward voltage fault threshold to 250mV, 500mV, or 1.5V, respectively. When the voltage across a MOSFET exceeds DVSD(FLT), the VSDFLT pin and at least one of the PWRFLT pins pull to GND. VDSFLT: MOSFET Fault Output. Open-drain output that pulls to GND when the forward voltage across either MOSFET exceeds DVSD(FLT). PWRFLT1 or PWRFLT2 also pulls low to indicate which MOSFET’s forward voltage drop exceeds DVSD(FLT). Otherwise, this pin is high impedance. Connect to GND if unused. 4355ff For more information www.linear.com/LTC4355 5 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.com/LTC4355 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. Using N-channel MOSFETs to replace Schottky diodes reduces the power dissipation and eliminates the need for costly heat sinks or large thermal layouts in high power applications. The LTC4355 is a positive voltage diode-OR controller that drives two external N-channel MOSFETs as pass transistors to replace ORing diodes. The IN and OUT pins form the anodes and cathodes of the ideal diodes. The source pins of the external MOSFETs are connected to the IN pins. The drains of the MOSFETs are connected together at the OUT pin, which is the positive supply of the device. The gates of the external MOSFETs are driven by the LTC4355 to regulate the voltage drop across the pass transistors. At power-up, the initial load current flows through the body diode of the MOSFET with the higher INx voltage. The associated GATEx pin immediately ramps up and turns on the MOSFET. The amplifier tries to regulate the voltage drop across the source and drain connections to 25mV. If the load current causes more than 25mV of drop, the MOSFET gate is driven fully on and the voltage drop is equal to RDS(ON) • ILOAD. When the power supply voltages are nearly equal, this regulation technique ensures that the load current is smoothly shared between the MOSFETs without oscil- lation. The current flowing through each pass transistor depends on the RDS(ON) of each MOSFET and the output impedances of the supplies. In the event of a supply failure, such as if the supply that is conducting most or all of the current is shorted to GND, reverse current flows temporarily through the MOSFET that is on. This current is sourced from any load capacitance and from the second supply through the body diode of the other MOSFET. The LTC4355 quickly responds to this condition, turning off the MOSFET in about 500ns. This fast turn-off prevents the reverse current from ramping up to a damaging level. In the case where the forward voltage drop exceeds the configurable fault threshold, DVSD(FLT), the VDSFLT pin pulls low. Using this pin to shunt current away from an LED or opto-coupler provides an indication that a pass transistor has either failed or has excessive forward current. Additionally, in this condition the PWRFLT1 or PWRFLT2 pin pulls low to identify the faulting channel. The PWRFLT pins also indicate if an input supply is within regulation. When VMON1 < 1.23V or VMON2 < 1.23V, the corresponding PWRFLT pin pulls low to indicate that the input supply is low, turning off an optional LED or optocoupler. The FUSEFLT pins indicate the status of input fuses. If the voltage at one of the IN pins is less than 3.5V, the corresponding FUSEFLT pin pulls low. The IN pins sink a minimum of 0.5mA to guarantee that the IN pin will pull low when the input fuse is blown open. Note that the FUSEFLT pin will activate if the input supply is less than 3.5V even if the fuse is intact. 4355ff For more information www.linear.com/LTC4355 7 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. The gate drive is limited to less than 18V. This allows the use of logic level threshold N-channel MOSFETs and standard N-channel MOSFETs above 20V. An external Zener diode can be used to clamp the potential from the MOSFET’s gate to source if the rated breakdown voltage is less than 18V. See the Typical Applications section for an example. The maximum allowable drain-source voltage, BVDSS, must be higher than the supply voltages. If an input is connected to GND, the full supply voltage will appear across the MOSFET. If the voltage drop across either MOSFET exceeds the configurable DVSD(FLT) fault threshold, the VDSFLT pin and the PWRFLT pin corresponding to the faulting channel pull low. The RDS(ON) should be small enough to conduct the maximum load current while not triggering a fault, and to stay within the MOSFET’s power rating at the maximum load current (I2 • RDS(ON)). Fault Conditions The LTC4355 monitors fault conditions and shunts current away from LEDs or opto-couplers, turning each one off to indicate a specific fault condition (see Table 1). When the voltage drop across the pass transistor is higher than the configurable DVSD(FLT) fault threshold, the internal pull-down at the VDSFLT pin and the PWRFLT1 or PWRFLT2 pin corresponding to the faulting channel turns on. The DVSD(FLT) threshold is configured by the SET pin. Tying SET to GND, tying SET to a 100k resistor connected to GND, or floating SET configures DVSD(FLT) to 250mV, 500mV, or 1.5V respectively. Fault conditions that may cause a high voltage across the pass transistor include: a MOSFET open on the higher supply, excessive MOSFET current due to overcurrent on the load or a shorted MOSFET on the lower supply. During startup or when a switchover between supplies occurs, the VDSFLT pin and PWRFLT1 or PWRFLT2 pin may momentarily indicate that the forward voltage has exceeded the programmed threshold during the short interval when the MOSFET gate ramps up and the body diode conducts. The PWRFLT pins are additionally used to indicate if either input supply is below its normal regulation range. If the voltage at the MON1 or MON2 pin is less than VMON(TH), typically 1.23V, the corresponding PWRFLT1 or PWRFLT2 pin will pull low. A resistive divider connected to the input supply drives the MON pin for the corresponding supply, configuring the PWRFLT threshold for that supply. Be sure to account for the tolerance of the MON pin threshold, the resistor tolerances, and the regulation range of the supply being monitored. Also, ensure that the voltage on the MON pin will not exceed 7V. The FUSEFLT pins are used to indicate the status of the input fuses. If one of the IN pins falls below VINx(TH), typically 3.5V, the FUSEFLT pin corresponding to that supply will pull low. The IN pins each sink a minimum of 0.5mA, enough to pull the pin low after an input fuse blows open. If there is a possibility that the MOSFET leakage current can be greater than 0.5mA, a resistor can be connected between the IN pin and GND to sink more current. Note that if the input supply voltage is less than VINx(TH) the FUSEFLT pin will pull low. Table 1. Fault Table DVSD1 < DVSD(FLT) VIN1 > 3.5V VMON1 > 1.23V VDSFLT* FUSEFLT1 PWRFLT1 True True True Hi-Z Hi-Z Hi-Z True True False Hi-Z Hi-Z Pull-Down True False True Hi-Z Pull-Down Hi-Z True False False Hi-Z Pull-Down Pull-Down False True True Pull-Down Hi-Z Pull-Down False True False Pull-Down Hi-Z Pull-Down False False True Pull-Down Pull-Down Pull-Down False False False Pull-Down Pull-Down Pull-Down *DVSD2 < DVSD(FLT) 4355ff 8 For more information www.linear.com/LTC4355 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. When the MOSFET finally commutates the reverse current the LTC4355 IN pin experiences a negative voltage spike, while the OUT pin spikes in the positive direction. The LTC4355 automatically supplies load current from the system input supply with the higher voltage. If this supply shorts to ground, reverse current begins to flow through the pass transistor temporarily and the transistor begins to turn off. When this reverse current creates –25mV of voltage drop across the drain and source pins of the pass transistor, a fast pull-down circuit engages to drive the gate low faster. The remaining system power supply delivers the load current through the body diode of its pass transistor until the channel turns on. The LTC4355 ramps the gate up with 20µA, turning on the N-channel MOSFET to reduce the voltage drop across it. To prevent damage to the LTC4355 under conditions of input short-circuit, protect the IN pins and OUT pin as shown in Figure 1. The IN pins are protected by clamping to the GND pin in the negative direction. Protect the OUT pin with a clamp, such as with a TVS or TransZorb, or with a local bypass capacitor of at least 10µF. In low voltage applications the MOSFET’s drain-source breakdown may be sufficient to protect the OUT pin, provided BVDSS + VIN < 100V. Input Short-Circuit Faults The dynamic behavior of an active, ideal diode entering reverse bias is most accurately characterized by a delay followed by a period of reverse recovery. During the delay phase some reverse current is built up, limited by parasitic resistances and inductances. During the reverse recovery phase, energy stored in the parasitic inductances is transferred to other elements in the circuit. Current slew rates during reverse recovery may reach 100A/µs or higher. VIN1 INPUT PARASITIC INDUCTANCE + – DIN1 SBR1U150SA REVERSE RECOVERY CURRENT M1 FDS3672 COUT OR 10µF REVERSE RECOVERY CURRENT INPUT SHORT VIN2 Parasitic inductance between the load bypass or the second supply and the LTC4355 allows a zero impedance input short to collapse the voltage at the OUT pin, which increases the total turn-off time (tOFF). For applications up to 30V, bypass the OUT pin with 39µF; above 30V use at least 100µF. One capacitor serves to guard against OUT collapse and also protect OUT from voltage spikes. INPUT PARASITIC INDUCTANCE – + OUTPUT PARASITIC INDUCTANCE + – DCLAMP SMAT70A VOUT CLOAD M2 FDS3672 DIN2 SBR1U150SA IN1 GATE1 IN2 GATE2 OUT LTC4355 GND 4355 F01 Figure 1. Reverse Recovery Produces Inductive Spikes at the IN and OUT Pins. The Polarity of Step Recovery Spikes Is Shown Across Parasitic Inductances 4355ff For more information www.linear.com/LTC4355 9 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. In the case when a MOSFET with less than 1000pF gate capacitance is chosen, a 1000pF compensation capacitor connected across the gate and source pins might be required. IR2 = Design Example VMONx(TH) +I R1(MIN) MONx (TH)(MAX) 1.245V = + 1µA = 100µA 12.7kΩ(−1%) The following design example demonstrates the calculations involved for selecting components in a 36V to 72V system with 5A maximum load current (see Figure 2). Use IR2 to choose R2. First, choose the N-channel MOSFET. The 100V, FDS3672 in the SO-8 package with RDS(ON) = 22mW(max) offers a good solution. The maximum voltage drop across it is: The LED D1, a Panasonic Green LN1351C, requires at least 1mA of current to fully turn on. Therefore, R5 is set to 33k to accommodate the lowest input supply voltage of 36V. The maximum power dissipation in the MOSFET is a mere: P = 5A • 110mV = 0.55W VIN1 = +48V M1 FDS3672 F2 7A VIN2 = +48V R2 340k R4 340k R5 33k IN1 SET MON2 R3 12.7k TO LOAD M2 FDS3672 GATE1 IN2 GATE2 OUT MON1 R1 12.7k 36V − 1.245V = 348kΩ 100µA Adjust R2 down by 1% to 344k to account for its tolerance. The next lower standard resistor value is R2 = 340k. DV = 5A • 22mΩ = 110mV F1 7A R2 = LTC4355 GND R6 33k VDSFLT FUSEFLT1 FUSEFLT2 PWRFLT1 PWRFLT2 GREEN LEDs PANASONIC LN1351C R7 33k D1 R8 33k D3 D2 GND R9 33k D5 D4 4355 F02 Figure 2. 36V to 72V/5A Design Example 4355ff 10 For more information www.linear.com/LTC4355 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. Check creepage and clearance guidelines to determine if this is an issue. Use no-clean solder to minimize PCB contamination. G 4355 F03 The inputs to the servo amplifiers, IN1, IN2, and OUT should be connected as closely as possible to the MOSFETs’ terminals for good accuracy. Figure 3. Layout Considerations 4355ff For more information www.linear.com/LTC4355 11 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.com/LTC4355 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 LTC4355 SMBT70A GND GND 4355 TA05 4355ff For more information www.linear.com/LTC4355 13 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 12.7k MON2 R4 33k IN2 GATE1 GATE2 OUT MON1 LTC4355 GND R5 33k VDSFLT FUSEFLT1 PWRFLT1 FUSEFLT2 PWRFLT2 D1 D3 GREEN LEDs PANASONIC LN1351C D2 GND 4355 TA04 4355ff 14 For more information www.linear.com/LTC4355 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 2.49k PG SCL SDAI SDAO ALERT PGIO PGI ADIN LTC4261 TMR VEE SENSE GATE DRAIN RAMP 330nF 330nF 33nF 47nF FDS3672 MEDIUM SHORT –48V_B HZS5C1 7A –48V_A 1µF GB VSS VSS DA DB GA VIN UVH UVL ADIN2 OV ON INTVCC FLTIN EN ADR1 ADR0 SS 10Ω 1M 1k 10nF 100V 7A FDS3672 8mΩ D: 1N4148WS IRF1310NS –48VOUT 4355 TA06 4355ff For more information www.linear.com/LTC4355 15 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 12.7k LOAD 12k VCC 100k LTC4354 DA GNDA GNDB 15A 15A DB 2k GA 2N2222 FAULT GB VSS 1µF 2k IRLR3110ZPbF IRLR3110ZPbF 4355 TA07 4355ff 16 For more information www.linear.com/LTC4355 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 ±0.10 1.70 ± 0.10 PIN 1 NOTCH R = 0.20 OR 0.35 × 45° CHAMFER PIN 1 TOP MARK (SEE NOTE 6) 0.200 REF 0.75 ±0.05 (DE14) DFN 0806 REV B 7 1 0.25 ± 0.05 0.50 BSC 3.00 REF 0.00 – 0.05 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 4355ff For more information www.linear.com/LTC4355 17 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 (.0197) BSC 0.305 ±0.038 (.0120 ±.0015) TYP 1.10 (.043) MAX DETAIL “A” 0.18 (.007) RECOMMENDED SOLDER PAD LAYOUT SEATING PLANE NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 0.17 – 0.27 (.007 – .011) TYP 1234567 8 0.86 (.034) REF 0.1016 ±0.0508 (.004 ±.002) 0.50 (.0197) BSC MSOP (MS16) 0213 REV A S Package 16-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610 Rev G) .386 – .394 (9.804 – 10.008) NOTE 3 .045 ±.005 .050 BSC 16 N 14 13 12 11 10 9 N .245 MIN .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) 1 .030 ±.005 TYP 15 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT 1 .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 2 3 4 5 .053 – .069 (1.346 – 1.752) NOTE: 1. DIMENSIONS IN .014 – .019 (0.355 – 0.483) TYP 7 8 .004 – .010 (0.101 – 0.254) 0° – 8° TYP .016 – .050 (0.406 – 1.270) 6 .050 (1.270) BSC S16 REV G 0212 INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE 4355ff 18 For more information www.linear.com/LTC4355 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 4355ff 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. For more information www.linear.com/LTC4355 19 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/ LTC4251-2 –48V Hot Swap Controllers in SOT-23 Fast Active Current Limiting, Supplies From –15V LTC4252-1/LTC4252-2/ LTC4252-A1/LTC4252-A2 –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 LT4256-1 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 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 LTC4357 Positive High Voltage Ideal Diode Controller Controls Single N-Channel MOSFET, 0.5µs Turn-Off, 80V Operation LTC4358 5A Ideal Diode Integrated N-Channel MOSFET, 0.5µs Turn-Off, 9V to 26.5V LTC4359 Ideal Diode Controller with Reverse Input Protection 4V to 80V Operation, –40V Input Protection, 150µA IQ 4355ff 20 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC4355 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC4355 LT 0813 REV F • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2007