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| PD - 94462E AFL27003R3S HIGH RELIABILITY HYBRID DC/DC CONVERTER Description The AFL Series of DC/DC converters feature high power density with no derating over the full military temperature range. This series is offered as part of a complete family of converters providing single and dual output voltages and operating from nominal +28 or +270 volt inputs with output power ranging from 80 to 120 watts. For applications requiring higher output power, multiple converters can be operated in parallel. The internal current sharing circuits assure equal current distribution among the paralleled converters. This series incorporates International Rectifier's proprietary magnetic pulse feedback technology providing optimum dynamic line and load regulation response. This feedback system samples the output voltage at the pulse width modulator fixed clock frequency, nominally 550 KHz. Multiple converters can be synchronized to a system clock in the 500 KHz to 700 KHz range or to the synchronization output of one converter. Undervoltage lockout, primary and secondary referenced inhibit, softstart and load fault protection are provided on all models. These converters are hermetically packaged in two enclosure variations, utilizing copper core pins to minimize resistive DC losses. Three lead styles are available, each fabricated with International Rectifier's rugged ceramic lead-to-package seal assuring long term hermeticity in the most harsh environments. Manufactured in a facility fully qualified to MIL-PRF38534, these converters are available in four screening grades to satisfy a wide range of requirements. The CH grade is fully compliant to the requirements of MIL-PRF38534 for class H. The HB grade is fully processed and screened to the class H requirement, but does not have material element evaluated to the class H requirement. Both grades are tested to meet the complete group "A" test specification over the full military temperature range without output power deration. Two grades with more limited screening are also available for use in less 270V Input, 3.3V Output AFL Features n n n n n n n n n n n n n n n n n 160 To 400 Volt Input Range 3.3 Volt Output High Power Density - 46 W / in3 66 Watt Output Power Parallel Operation with Stress and Current Sharing Low Profile (0.380") Seam Welded Package Ceramic Feedthru Copper Core Pins High Efficiency - to 74% Full Military Temperature Range Continuous Short Circuit and Overload Protection Remote Sensing Terminals Primary and Secondary Referenced Inhibit Functions Line Rejection > 60 dB - DC to 50KHz External Synchronization Port Fault Tolerant Design Dual Output Versions Available Standard Military Drawings Available demanding applications. Variations in electrical, mechanical and screening can be accommodated. Contact IR Santa Clara for special requirements. www.irf.com 1 09/01/04 AFL27003R3S Specifications ABSOLUTE MAXIMUM RATINGS Input Voltage Soldering Temperature Case Temperature -0.5V to 500V 300C for 10 seconds Operating Storage -55C to +125C -65C to +135C Electrical Performance Characteristics -55C < TCASE < +125C, 160V< VIN < 400V unless otherwise specified. Parameter INPUT VOLTAGE OUTPUT VOLTAGE 1 2, 3 OUTPUT CURRENT OUTPUT POWER MAXIMUM CAPACITIVE LOAD OUTPUT VOLTAGE TEMPERATURE COEFFICIENT OUTPUT VOLTAGE REGULATION Line Load OUTPUT RIPPLE VOLTAGE 1, 2, 3 INPUT CURRENT No Load Inhibit 1 Inhibit 2 INPUT RIPPLE CURRENT 1, 2, 3 CURRENT LIMIT POINT Expressed as a Percentage of Full Rated Load LOAD FAULT POWER DISSIPATION Overload or Short Circuit EFFICIENCY 1, 2, 3 SWITCHING FREQUENCY ISOLATION MTBF 1, 2, 3 1 Input to Output or Any Pin to Case (except Pin 3). Test @ 500VDC MIL-HDBK-217F, AIF @ TC = 40C 1 2 3 1, 2, 3 VIN = 270 Volts 1 2, 3 1, 2, 3 1, 2, 3 1, 2, 3 1, 2, 3 4 VIN = 160, 270, 400 Volts, Note 6 Note 6 Note 1 VIN = 270 Volts, 100% Load - Note 1, 6 10,000 -0.015 +0.015 Group A Subgroups Note 6 VIN = 270 Volts, 100% Load 3.27 3.23 3.30 3.33 3.37 20 66 V V A W fd %/C Test Conditions Min 160 Nom 270 Max 400 Unit V No Load, 50% Load, 100% Load VIN = 160, 270, 400 Volts VIN = 160, 270, 400 Volts, 100% Load, BW = 10MHz VIN = 270 Volts IOUT = 0 Pin 4 Shorted to Pin 2 Pin 12 Shorted to Pin 8 VIN = 270 Volts, 100% Load B.W. = 10MHz VOUT = 90% VNOM Note 5 -10.0 -35.0 +10.0 +35.0 30 15.0 17.0 3.00 5.00 60 mV mV mVpp mA mA mA mA mApp 115 105 125 125 115 140 30 % % % W VIN = 270 Volts, 100% Load 72 500 100 300 74 550 600 % KHz M KHrs For Notes to Specifications, refer to page 3 2 www.irf.com AFL27003R3S Elecrical Performance Characteristics (Continued) Parameter ENABLE INPUTS (Inhibit Function) Converter Off Sink Current Converter On Sink Current SYNCHRONIZATION INPUT Frequency Range Pulse Amplitude, Hi Pulse Amplitude, Lo Pulse Rise Time Pulse Duty Cycle LOAD TRANSIENT RESPONSE Amplitude Recovery Amplitude Recovery LINE TRANSIENT RESPONSE Amplitude Recovery TURN-ON CHARACTERISTICS Overshoot Delay LOAD FAULT RECOVERY LINE REJECTION 4, 5, 6 4, 5, 6 4, 5, 6 4, 5, 6 4, 5, 6 4, 5, 6 Group A Subgroups 1, 2, 3 1, 2, 3 Test Conditions Logical Low, Pin 4 or Pin 12 Note 1 Logical High, Pin 4 and Pin 12 - Note 9 Note 1 Min -0.5 2.0 Nom Max 0.8 100 50 100 700 10 0.8 100 80 Unit V A V A KHz V V nSec % 1, 2, 3 1, 2, 3 1, 2, 3 Note 1 Note 1 Note 2, 8 Load Step 50% 100% Load Step 10% 50% Note 1, 2, 3 VIN Step = 160 400 Volts VIN = 160, 270, 400 Volts. Note 4 Enable 1, 2 on. (Pins 4, 12 high or open) Same as Turn On Characteristics. MIL-STD-461, CS101, 30Hz to 50KHz Note 1 500 2.0 -0.5 20 -450 -450 450 200 450 400 mV Sec mV Sec -500 500 500 mV Sec 50 75 250 120 mV mSec 60 70 dB Notes to Specifications: 1. 2. 3. 4. 5. 6. 7. 8. 9. Parameters not 100% tested but are guaranteed to the limits specified in the table. Recovery time is measured from the initiation of the transient to where VOUT has returned to within 1% of VOUT at 50% load. Line transient transition time 100 Sec. Turn-on delay is measured with an input voltage rise time of between 100 and 500 volts per millisecond. Current limit point is that condition of excess load causing output voltage to drop to 90% of nominal. Parameter verified as part of another test. All electrical tests are performed with the remote sense leads connected to the output leads at the load. Load transient transition time 10 Sec. Enable inputs internally pulled high. Nominal open circuit voltage 4.0VDC. www.irf.com 3 AFL27003R3S AFL27003R3S Circuit Description Figure I. AFL Single Output Block Diagram DC INPUT 1 INPUT FILTER ENABLE 1 4 PRIMARY BIAS SUPPLY OUTPUT FILTER 7 10 + OUTPUT + SENSE CURRENT SENSE SYNC OUTPUT 5 CONTROL SYNC INPUT 6 ERROR AMP & REF SHARE AMPLIFIER 11 12 SENSE AMPLIFIER SHARE ENABLE 2 CASE 3 9 8 - SENSE OUTPUT RETURN INPUT RETURN 2 Circuit Operation and Application Information The AFL series of converters employ a forward switched mode converter topology. (refer to Figure I.) Operation of the device is initiated when a DC voltage whose magnitude is within the specified input limits is applied between pins 1 and 2. If pin 4 is enabled (at a logical 1 or open) the primary bias supply will begin generating a regulated housekeeping voltage bringing the circuitry on the primary side of the converter to life. Two power MOSFETs used to chop the DC input voltage into a high frequency square wave, apply this chopped voltage to the power transformer. As this switching is initiated, a voltage is impressed on a second winding of the power transformer which is then rectified and applied to the primary bias supply. When this occurs, the input voltage is shut out and the primary bias voltage becomes exclusively internally generated. The switched voltage impressed on the secondary output transformer winding is rectified and filtered to provide the converter output voltage. An error amplifier on the secondary side compares the output voltage to a precision reference and generates an error signal proportional to the difference. This error signal is magnetically coupled through the feedback transformer into the controller section of the converter varying the pulse width of the square wave signal driving the MOSFETs, narrowing the width if the output voltage is too high and widening it if it is too low. not used, the sense leads should be connected to their respective output terminals at the converter. Figure III. illustrates a typical application. Inhibiting Converter Output As an alternative to application and removal of the DC voltage to the input, the user can control the converter output by providing TTL compatible, positive logic signals to either of two enable pins (pin 4 or 12). The distinction between these two signal ports is that enable 1 (pin 4) is referenced to the input return (pin 2) while enable 2 (pin 12) is referenced to the output return (pin 8). Thus, the user has access to an inhibit function on either side of the isolation barrier. Each port is internally pulled "high" so that when not used, an open connection on both enable pins permits normal converter operation. When their use is desired, a logical "low" on either port will shut the converter down. Figure II. Enable Input Equivalent Circuit +5.6V 100K Pin 4 or Pin 12 1N4148 Remote Sensing Connection of the + and - sense leads at a remotely locatled load permits compensation for resistive voltage drop between the converter output and the load when they are physically separated by a significant distance. This connection allows regulation to the placard voltage at the point of application.When the remote sensing features is 290K 2N3904 150K Pin 2 or Pin 8 Disable 4 www.irf.com AFL27003R3S Internally, these ports differ slightly in their function. In use, a low on Enable 1 completely shuts down all circuits in the converter while a low on Enable 2 shuts down the secondary side while altering the controller duty cycle to near zero. Externally, the use of either port is transparent to the user save for minor differences in idle current. (See specification table). high level of +2.0 volts. The sync output of another converter which has been designated as the master oscillator provides a convenient frequency source for this mode of operation. When external synchronization is not required, the sync in pin should be left unconnected thereby permitting the converter to operate at its' own internally set frequency. The sync output signal is a continuous pulse train set at 550 50 KHz, with a duty cycle of 15 5%. This signal is referenced to the input return and has been tailored to be compatible with the AFL sync input port. Transition times are less than 100 ns and the low level output impedance is less than 50 ohms. This signal is active when the DC input voltage is within the specified operating range and the converter is not inhibited. This output has adequate drive reserve to synchronize at least five additional converters. A typical synchronization connection option is illustrated in Figure III. Synchronization of Multiple Converters When operating multiple converters, system requirements often dictate operation of the converters at a common frequency. To accommodate this requirement, the AFL series converters provide both a synchronization input and output. The sync input port permits synchronization of an AFL converter to any compatible external frequency source operating between 500 and 700 KHz. This input signal should be referenced to the input return and have a 10% to 90% duty cycle. Compatibility requires transition times less th an100 ns, maximum low level of +0.8 volts and a minimum Figure III. Preferred Connection for Parallel Operation Power Input 1 12 Vin Rtn Case Enable 1 Sync Out Sync In 6 Enable 2 Share AFL + Sense - Sense Return + Vout 7 Optional Synchronization Connection Share Bus 1 12 Vin Rtn Case Enable 1 Sync Out Sync In 6 Enable 2 Share AFL + Sense - Sense Return + Vout 7 to Load 1 Vin Rtn Case Enable 1 Sync Out Sync In 6 Enable 2 Share 12 AFL + Sense - Sense Return + Vout 7 (Other Converters) Parallel Operation-Current and Stress Sharing Figure III. illustrates the preferred connection scheme for operation of a set of AFL converters with outputs operating in parallel. Use of this connection permits equal sharing of a load current exceeding the capacity of an individual AFL among the members of the set. An important feature of the AFL series operating in the parallel mode is that in addition to sharing the current, the stress induced by temperature will also be shared. Thus if one member of a paralleled set is operating at a higher case temperture, the current it provides to the load will be reduced as compensation for the temperature induced stress on that device. www.irf.com 5 AFL27003R3S When operating in the shared mode, it is important that symmetry of connection be maintained as an assurance of optimum load sharing performance. Thus, converter outputs should be connected to the load with equal lengths of wire of the same gauge and sense leads from each converter should be connected to a common physical point, preferably at the load along with the converter output and return leads. All converters in a paralleled set must have their share pins connected together. This arrangement is diagrammatically illustrated in Figure III. showing the outputs and sense pins connected at a star point which is located close as possible to the load. As a consequence of the topology utilized in the current sharing circuit, the share pin may be used for other functions. In applications requiring a single converter, the voltage appearing on the share pin may be used as a "current monitor". The share pin open circuit voltage is nominally +1.00v at no load and increases linearly with increasing output current to +2.20v at full load. The share pin voltage is referenced to the output return pin. for minor variations of either surface. While other available types of heat conductive materials and compounds may provide similar performance, these alternatives are often less convinient and are frequently messy to use. A conservative aid to estimating the total heat sink surface area (A HEAT SINK) required to set the maximum case temperature rise (T) above ambient temperature is given by the following expression: . T -143 A HEAT SINK - 3.0 80P 0.85 where T = Case temperature rise above ambient 1 P = Device dissipation in Watts = POUT - 1 Eff As an example, it is desired to maintain the case temperature of an AFL27015S at +85C in an area where the ambient temperature is held at a constant +25C; then Thermal Considerations Because of the incorporation of many innovative technological concepts, the AFL series of converters is capable of providing very high output power from a package of very small volume. These magnitudes of power density can only be obtained by combining high circuit efficiency with effective methods of heat removal from the die junctions. This requirement has been effectively addressed inside the device; but when operating at maximum loads, a significant amount of heat will be generated and this heat must be conducted away from the case. To maintain the case temperature at or below the specified maximum of 125C, this heat must be transferred by conduction to an appropriate heat dissipater held in intimate contact with the converter base-plate. Because effectiveness of this heat transfer is dependent on the intimacy of the baseplate/heatsink interface, it is strongly recommended that a high thermal conductivity heat transferance medium is inserted between the baseplate and heatsink. The material most frequently utilized at the factory during all testing and burn-in processes is sold under the trade name of Sil-Pad(R) 4001 . This particular pro duct is an insulator but electrically conductive versions are also available. Use of these materials assures maximum surface contact with the heat dissipator thereby compensating T = 85 - 25 = 60C From the Specification Table, the worst case full load efficiency for this device is 83%; therefore the power dissipation at full load is given by 1 P = 120 * - 1 = 120 * ( 0.205) = 24.6 W .83 and the required heat sink area is . -143 60 - 3.0 = 71 in 2 A HEAT SINK = 80 * 24.6 0.85 Thus, a total heat sink surface area (including fins, if any) of 71 in2 in this example, would limit case rise to 60C above ambient. A flat aluminum plate, 0.25" thick and of approximate dimension 4" by 9" (36 in2 per side) would suffice for this application in a still air environment. Note that to meet the criteria in this example, both sides of the plate require unrestricted exposure to the ambient air. 1Sil-Pad is a registered Trade Mark of Bergquist, Minneapolis, MN 6 www.irf.com AFL27003R3S Input Filter The AFL270XXS series converters incorporate a LC input filter whose elements dominate the input load impedance characteristic at turn-on. The input circuit is as shown in Figure IV. Finding a resistor value for a particular output voltage, is simply a matter of substituting the desired output voltage and the nominal device voltage into the equation and solving for the corresponding resistor value. Figure IV. Input Filter Circuit 8.4H Pin 1 0.54fd Figure V. Connection for VOUT Adjustment Enable 2 Share AFL270xxS + Sense - Sense Return RADJ To Load + Vout Pin 2 Caution: Do not set Radj < 500 Undervoltage Lockout A minimum voltage is required at the input of the converter to initiate operation. This voltage is set to 150 5 volts. To preclude the possibility of noise or other variations at the input falsely initiating and halting converter operation, a hysteresis of approximately 10 volts is incorporated in this circuit. Thus if the input voltage droops to 140 4 volts, the converter will shut down and remain inoperative until the input voltage returns to 150 volts. Attempts to adjust the output voltage to a value greater than 120% of nominal should be avoided because of the potential of exceeding internal component stress ratings and subsequent operation to failure. Under no circumstance should the external setting resistor be made less than 500. By remaining within this specified range of values, completely safe operation fully within normal component derating limits is assured. Examination of the equation relating output voltage and resistor value reveals a special benefit of the circuit topology utilized for remote sensing of output voltage in the AFL270XXS series of converters. It is apparent that as the resistance increases, the output voltage approaches the nominal set value of the device. In fact the calculated limiting value of output voltage as the adjusting resistor becomes very large is 25mV above nominal device voltage. The consequence is that if the +sense connection is unintentionally broken, an AFL270XXS has a fail-safe output voltage of Vout + 25mV, where the 25mV is independent of the nominal output voltage. It can be further demonstrated that in the event of both the + and - sense connections being broken, the output will be limited to Vout + 440mV. This 440 mV is also essentially constant independent of the nominal output voltage. While operation in this condition is not damaging to the device, not at all performance parameters will be met. Output Voltage Adjust In addition to permitting close voltage regulation of remotely located loads, it is possible to utilize the converter sense pins to incrementally increase the output voltage over a limited range. The adjustments made possible by this method are intended as a means to "trim" the output to a voltage setting for some particular application, but are not intended to create an adjustable output converter. These output voltage setting variations are obtained by connecting an appropriate resistor value between the +sense and -sense pins while connecting the -sense pin to the output return pin as shown in Figure V. below. The range of adjustment and corresponding range of resistance values can be determined by use of the following equation. VNOM Radj = 100 * VOUT - VNOM -.025 Where VNOM = device nominal output voltage, and VOUT = desired output voltage www.irf.com 7 AFL27003R3S AFL27003R3S Case Outlines Case X Case W Pin Variation of Case Y 3.000 2.760 o 0.128 0.050 0.250 0.250 0.050 12 7 0.25 typ 12 7 BERYLLIA WARNING: These converters are hermetically sealed; however they contain BeO substrates and should not be ground or subjected to any other operations including exposure to acids, which may produce Beryllium dust or fumes containing Beryllium 1 6 1.260 1.500 1.000 Ref 0.200 Typ Non-cum Pin o 0.040 1.000 2.500 0.220 0.220 2.800 0.525 Pin o 0.040 2.975 max 0.238 max 0.380 Max 0.42 0.380 Max Case Y 1.150 0.300 o 0.140 0.050 Case Z Pin Variation of Case Y 0.050 0.250 0.250 1 6 1.500 1.750 2.00 1.000 Ref 0.200 Typ Non-cum Pin o 0.040 1.000 Ref 1.750 2.500 2.975 max 0.238 max 0.375 0.220 0.220 0.36 2.800 0.525 Pin o 0.040 0.380 Max 0.380 Max Tolerances, unless otherwise specified: .XX .XXX = = 0.010 0.005 8 www.irf.com AFL27003R3S Available Screening Levels and Process Variations for AFL27003R3S Series. Requirement Temperature Range Element Evaluation Internal Visual Temperature Cycle Constant Acceleration Burn-in Final Electrical (Group A) Seal, Fine & Gross External Visual 2017 1010 2001 1015 MIL-PRF-38534 & Specification 1014 2009 48hrs @ 85C 25C Cond C MIL-STD-883 Method No Suffix -20 to +85C ES Suffix -55C to +125C HB Suffix -55C to +125C CH Suffix -55C to +125C MIL-PRF-38534 9 Cond B 500g 48hrs @ 125C 25C Cond A, C 9 Cond C Cond A 160hrs @ 125C -55, +25, +125C Cond A, C 9 Cond C Cond A 160hrs @ 125C -55, +25, +125C Cond A, C 9 9 9 * per Commercial Standards AFL27003R3S Pin Designation Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 Part Numbering Designation Positive Input Input Return Case Enable 1 Sync Output Sync Input Positive Output Output Return Return Sense Positive Sense Share Enable 2 AFL 270 03R3 S X / CH Model Input Voltage 270 = 270V 28 = 28V Screening Case Style W, X, Y, Z - , ES HB, CH Output Voltage 03R3 = 3.3V Outputs S = Single D = Dual WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, Tel: (310) 252-7105 IR SANTA CLARA: 2270 Martin Av., Santa Clara, California 95050, Tel: (408) 727-0500 Visit us at www.irf.com for sales contact information. Data and specifications subject to change without notice. 09/2004 www.irf.com 9 |
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