ADDC02803SC AD | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 18
Technical content
+VOUT RETURN + SENSE ADJUST STATUS VAUX INHIBIT SYNC ISHARE TEMP –VIN +VIN FIXED FREQUENCY DUAL INTERLEAVED POWER TRAIN – SENSE RETURN RETURN +VOUT +VOUT OUTPUT FILTER OUTPUT SIDE CONTROL CIRCUIT INPUT SIDE CONTROL CIRCUIT EMI FILTER ADDC02803SC ADDC02805SA REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. a ADDC02803SC/ADDC02805SA
FEATURES
28 V dc Input, 5 V dc @ 20 A, 100 W Output
(ADDC02805SA) 28 V dc Input, 3.3 V dc @ 20 A, 66 W Output (ADDC02803SC) Integral EMI Filter Designed to Meet MIL-STD-461D Low Weight: 80 Grams NAVMAT Derated Many Protection and System Features
APPLICATIONS
Commercial and Military Airborne Electronics Missile Electronics Space-Based Antennae and Vehicles Mobile/Portable Ground Equipment Distributed Power Architecture for Active Array Radar GENERAL DESCRIPTION The ADDC02803SC and ADDC02805SA hybrid dc/dc con- verters with integral EMI filters offer the highest power density of any dc/dc converter with their features and in their power range available today. The converters with integral EMI filters are fixed frequency, 1 MHz square wave switching dc/dc power supplies. They are not variable frequency resonant converters. In addition to many protection features, these converters have system level features that allow them to be used as components in larger systems as well as stand-alone power supplies. The units are designed for high reliability and high performance applications where saving space and/or weight are critical. The ADDC02803SC and ADDC02805SA are available in three screening grades; all grades use a hermetically sealed, molybdenum based hybrid package. Three screening levels are available, including military SMD.
28 V/66 W/100 W DC/DC Converters
- Up to 60 W/cubic inch power density with an integral EMI filter designed to meet all applicable requirements in MIL- STD-461D when installed in a typical system setup. 2. Light weight: 80 grams 3. Operational and survivable over a wide range of input condi- tions: 16 V–50 V dc; survives low line, high line and positive and negative transients. See section entitled: Input Voltage Range. 4. High reliability; NAVMAT derated 5. Protection features include: Output Overvoltage Protection Output Short Circuit Current Protection Thermal Monitor/Shutdown Input Overvoltage Shutdown Input Transient Protection 6. System level features include: Current Sharing for Parallel Operation Inhibit Control Output Status Signal Synchronization for Multiple Units Input Referenced Auxiliary Voltage Supply Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1998
ADDC02803SC/ADDC02805SA–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Case Test ADDC02803SC ADDC02805SA Parameter Temp Level Conditions Min Typ Max Min Typ Max Units INPUT CHARACTERISTICS Steady State Operating Input Voltage Range1 Full VI I O = 2 A to 20 A 18 28 40 18 28 40 V Abnormal Operating Input Voltage Range (Per MIL-STD-704D)1 Full VI I O = 2 A to 16 A 16 50 16 50 V Input Overvoltage Shutdown +25 °C I 50 52.5 55 50 52.5 55 V No Load Input Current +25 °C I 90 90 mA Disabled Input Current Full VI 0.85 2.0 0.85 2.0 mA OUTPUT CHARACTERISTICS2, 3 Full VI I O = 2 A to 20 A, VIN = 18 V to 40 V dc 3.2 3.4 4.925 5.125 V Full VI I O = 2 A to 16 A, VIN = 16 V to 50 V dc 3.2 3.4 4.925 5.125 V Line Regulation +25 °CV I O = 20 A, VIN = 18 V to 40 V dc 1 1 mV Load Regulation +25 °CV V IN = 28 V dc, IO = 2 A to 20 A 1 1 mV Output Ripple/Noise4 +25°CI I O = 20 A, 5 kHz – 2 MHz BW 15 35 15 50 mV p-p Output Current (IO) Full VI V IN = 18 V to 40 V dc 2 21.2 2 20 A Output Overvoltage Protection +25 °CV I O = 20 A, Open Remote Sense Connection 145 125 % V O Nom Output Current Limit +25 °CV V O = 90% VOUT Nom 130 % I O max Output Short Circuit Current +25 °C I 39 35 A ISOLATION CHARACTERISTICS Isolation Resistance +25 °C I Input to Output or Any Pin to Case at 500 V dc 100 100 M W DYNAMIC CHARACTERISTICS4 Output Voltage Deviation Due to Step Change in Load +25 °CV I O = 10 A to 20 A or 20 A to 10 A di/dt = 0.5 A/ms 350 500 mV Response Time Due to Step Change in Load +25 °CV I O = 10 A to 20 A or 20 A to 10 A, di/dt = 0.5 A/ms, 135 125 ms Time for VOUT to Return within 2% of Final Value Soft Start Turn-On Time5 +25°CI I O = 20 A, From Inhibit High to Status High 1 4 7 20 ms THERMAL CHARACTERISTICS Efficiency +25 °CI I O = 12 A 75 79 77 80 % Max VI I O = 12 A 75 77 % Min VI I O = 12 A 72 75 % +25°CI I O = 20 A 74 77 77 79 % Max VI I O = 20 A 74 77 % Min VI I O = 20 A 73 75 % Hottest Junction Temperature6 +90°CV I O = 20 A 110 110 °C CONTROL CHARACTERISTICS Clock Frequency Full VI I O = 2 A 0.85 0.99 0.85 0.99 MHz STATUS (Pin 4) VOH +25°CI I OH = 400 mA 2.4 4.0 2.4 4.0 V VOL +25°CI I OL = 1 mA 0.15 0.7 0.15 0.7 V VAUX (Pin 5) INHIBIT (Pin 6) VIL +25°C I 0.5 0.5 V IIL +25°CI V IL = 0.5 V 1.2 1.2 mA VI (Open Circuit) +25 °C I 15 15 V SYNC (Pin 7)7 VIH +25°C I 4.0 4.0 V IIH +25°CI V IH = 7.0 V 175 175 mA TEMP (Pin 9) +25 °C V 3.90 3.90 V NOTES 150 V dc upper limit rated for transient condition of up to 50 ms. 16 V dc lower limit rated for continuous operation during em ergency condition. Steady state and abnormal input voltage range require source impedance sufficient to insure input stability at low line. See sections entitled S ystem Instability Considerations and Input Voltage Range. 2Measured at the remote sense points. 3Unit regulates output voltage to zero load. 4CLOAD = 0. 5Output is fully loaded into a constant resistive load. 6Refer to section entitled Thermal Characteristics for more information. 7Unit has internal pull-down; refer to section entitled Pin 7 (SYNC). Specifications subject to change without notice. REV. A–2– (TC = +258C, VIN = 28 V dc 6 0.5 V dc, unless otherwise noted; full temperature range is –558C to +908C; all temperatures are case and T C is the temperature measured at the center of the package bottom.)
REV. A –3– ABSOLUTE MAXIMUM RATINGS* *Absolute maximum ratings are limiting values, to be applied individually, and beyond which the serviceability of the circuit may be impaired. Functional operability under any of these conditions is not necessarily implied. Exposure of absolute maximum rating conditions for extended periods of time may affect device reliability.
ORDERING INFORMATION
Device Range (Case) Description ADDC02803SCKV –40 °C to +85°C Hermetic Package ADDC02803SCTV –55 °C to +90°C Hermetic Package 5962-9760101HXC (ADDC2803SCTV/QMLH) –55 °C to +125°C Hermetic Package ADDC02805SAKV –40 °C to +85°C Hermetic Package ADDC02805SATV –55 °C to +90°C Hermetic Package 5962-9570701HXC (ADDC2805SATV/QMLH) –55 °C to +125°C Hermetic Package EXPLANATION OF TEST LEVELS Test Level I – 100% production tested. II – 100% production tested at +25 °C, and sample tested at specified temperatures. III – Sample tested only. IV – Parameter is guaranteed by design and characterization testing. V – Parameter is a typical value only. VI – All devices are 100% production tested at +25 °C. 100% production tested at temperature extremes for military temperature devices; guaranteed by design and charac- terization testing for industrial devices. PIN DESCRIPTIONS Pin No. Name Function 1 –SENSE Feedback loop connection for remote sensing output voltage. Must always be connected to output return for proper operation. 2 +SENSE Feedback loop connection for remote sensing output voltage. Must always be connected to OUT for proper operation. 3 ADJUST Adjusts output voltage setpoint.
4 STATUS Indicates output voltage is within – 5% of
nominal. Active high referenced to –SENSE (Pin 1). 5V AUX Low level dc auxiliary voltage supply refer- enced to input return (Pin 10). 6 INHIBIT Power Supply Inhibit. Active low and refer- enced to input return (Pin 10).
7 SYNC Clock synchronization input for multiple
units; referenced to input return (Pin 10). 8I SHARE Current share pin which allows paralleled units to share current typically within – 5% at full load; referenced to input return (Pin 10).
9 TEMP Case temperature indicator and temperature
shutdown override; referenced to input return (Pin 10). 10 –V IN Input Return. 11 +V IN +28 V Nominal Input Bus. 12 +V OUT +5 V dc Output (ADDC02805SA). +3.3 V dc Output (ADDC02803SC). 13 +V OUT +5 V dc Output (ADDC02805SA). +3.3 V dc Output (ADDC02803SC). 14 +V OUT +5 V dc Output (ADDC02805SA). +3.3 V dc Output (ADDC02803SC). 15 RETURN Output Return. 16 RETURN Output Return. 17 RETURN Output Return. CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. PIN CONFIGURATION 11 12 TOP VIEW WARNING! ESD SENSITIVE DEVICE
Figure 4. Low Line Dropout vs. Load at +90 °C Case
4.950 VOUT
Figure 5. Output Voltage vs. Case Temperature ( °C) Figure 6. Output Voltage vs. Case Temperature ( °C) Figure 1. Efficiency vs. Line and Load at +25 °C Figure 2. Efficiency vs. Line and Load at +25 °C Figure 3. Efficiency vs. Case Temperature ( °C)
Figure 13. Incremental Input Impedance (Magnitude) Figure 14. Incremental Input Impedance (Magnitude) Figure 15. Incremental Output Impedance (Magnitude) Figure 16. Incremental Output Impedance (Magnitude)
2.00 MHz/DIV
Figure 17. Output Voltage Ripple Spectrum Figure 18. Output Voltage Ripple Spectrum
Figure 19. Conducted Emissions, MIL-STD-461D, CE101, Figure 20. Conducted Emissions, MIL-STD-461D, CE102, Figure 21. Radiated Emissions, MIL-STD-461D, RE101,
100 W Load
Figure 22. Radiated Emissions, MIL-STD-461D, RE102, INTRODUCED BY THE LISNs. REFER TO SECTION ON EMI CONSIDERATIONS FOR MORE INFORMATION. Figure 23. S chematic of Test Setup for EMI Measurements
REV. A –11– before it falls below 50 V. In both cases, the ADDC02803SC/ ADDC02805SA can be modified to operate to specification up to the 50 V input voltage limit and to shut down and protect itself during the time the input voltage exceeds 50 V. When the input voltage falls below 50 V as the surge ends, the converter will automatically initiate a soft start. In order to survive these higher input voltage surges, the modified converter will no longer have input transient protection, however, as described below. Contact the factory for information on units surviving high input voltage surges. Input Voltage Transient Protection: The converter has a transient voltage suppressor connected across its input leads to protect the unit against high voltage pulses (both positive and negative) of short duration. With the power supply connected in the typical system setup shown in Figure 23, a transient voltage pulse is created across the converter in the following manner. A 20 mF capacitor is first charged to 400 V. It is then directly connected across the converter’s end of the two meter power lead cable through a 2 W on-state resistance MOSFET. The duration of this connection is 10 ms. The pulse is repeated every second for 30 minutes. This test is repeated with the connection of the 20 mF capacitor reversed to create a negative pulse on the supply leads. (If continuous reverse voltage protection is required, a diode can be added externally in series at the expense of lower efficiency for the power system.) The converter responds to this input transient voltage test by shutting down due to its input overvoltage protection feature. Once the pulse is over, the converter initiates a soft-start, which is completed before the next pulse. No degradation of converter performance occurs. THERMAL CHARACTERISTICS Junction and Case Temperatures: It is important for the user to know how hot the hottest semiconductor junctions within the converter get, and to understand the relationship between junction, case and ambient temperatures. The hottest semiconductors in the 100 W product line of Analog Devices’ high density power supplies are the switching MOSFETs and the output rectifiers. There is an area inside the main power transformers that is hotter than these semiconductors, but it is within NAVMAT guidelines and well below the Curie tempera- ture of the ferrite. (The Curie temperature is the point at which the ferrite begins to lose its magnetic properties.) Since NAVMAT guidelines require that the maximum junction temperature be 110°C, the power supply manufacturer must specify the temperature rise above the case for the hottest semi- conductors so the user can determine the case temperature required to meet NAVMAT guidelines. The thermal charac- teristics section of the specification table states the hottest junc- tion temperature for maximum output power at a specified case temperature. The unit can operate to case temperatures higher than 90°C, but 90°C is the maximum temperature that permits NAVMAT guidelines to be met. Case and Ambient Temperatures: It is the user’s responsi- bility to properly heat sink the power supply in order to maintain the appropriate case temperature and, in turn, the maximum junction temperature. Maintaining the appropriate case tem- perature is a function of the ambient temperature and the me- chanical heat removal system. The static relationship of these variables is established by the following formula: TC = TA + (PD · RqCA where: TC = case temperature measured at the center of the pack- age bottom, TA = ambient temperature of the air available for cooling, PD = the power, in watts, dissipated in the power supply, RqCA = the thermal resistance from the center of the package to free air, or case to ambient. The power dissipated in the power supply, PD, can be calcu- lated from the efficiency, h, given in the data sheets, and the actual output power, PO, in the user’s application by the fol- lowing formula: PD = PO h ±1æ Łç ö For example, at 80 W of output power and 80% efficiency, the power dissipated in the power supply is 20 W. If under these conditions, the user wants to maintain NAVMAT deratings (i.e., a case temperature of approximately 90 °C) with an ambi- ent temperature of 75 °C, the required thermal resistance, case to ambient, can be calculated as 90 = 75 + (20 · RqCA) or RqCA = 0.75°C/W This thermal resistance, case to ambient, will determine what kind of heat sink and whether convection cooling or forced air cooling is required to meet the constraints of the system. SYSTEM INSTABILITY CONSIDERATIONS In a distributed power supply architecture, a power source provides power to many “point-of-load” (POL) converters. At low frequencies, the POL converters appear incrementally as negative resistance loads. This negative resistance could cause system instability problems. Incremental Negative Resistance: A POL converter is de- signed to hold its output voltage constant no matter how its input voltage varies. Given a constant load current, the power drawn from the input bus is therefore also a constant. If the input voltage increases by some factor, the input current must decrease by the same factor to keep the power level constant. In incremental terms, a positive incremental change in the input voltage results in a negative incremental change in the input current. The POL converter therefore looks, incremen- tally, like a negative resistor. The value of this negative resistor at a particular operating point, V IN, IIN, is: RN = ±VIN IIN Note that this resistance is a function of the operating point. At full load and low input line, the resistance is its smallest, while at light load and high input line, it is its largest.
resistor, RS, the network of Figure 33 results. Figure 33. Model of Power Source and POL Converter lute value of RN is smallest at this operating condition. place a small resistor in series with this extra capacitor. resistance” to the LC network. latory, or it may cause the entire system to be unstable. converter for frequencies into the several kHz range. makes the following exceptions.
REV. A –13– supply. A lower voltage rating capacitor (500 V) was therefore chosen to fit more capacitance in the same space in order to better meet the conducted emissions requirement of MIL-STD- 461D (CE102). For those applications requiring 250 V or less of isolation from input to output, the present designs would meet NAVMAT guidelines. Switching Transistors: 100 V MOSFETs are used in the standard unit to switch the primary side of the transformers. Their nominal off-state voltage meets the NAVMAT derating guidelines. When the MOSFETs are turned off, however, mo- mentary spikes occur that reach 100 V. The present generation of MOSFETs are rated for repetitive avalanche, a condition that was not considered by the NAVMAT deratings. In the worst case condition, the energy dissipated during avalanche is 1% of the device’s rated repetitive avalanche energy. To meet the NAVMAT derating, 200 V MOSFETs could be used. The
100 V MOSFETs are used instead for their lower on-state resis-
tance, resulting in higher efficiency for the power supply. NAVMAT Junction Temperatures: The two types of power deratings (current and temperature) can be independent of one another. For instance, a switching diode can meet its derating of 70% of its maximum current, but its junction temperature can be higher than 110 °C if the case temperature of the con- verter, which is not controlled by the manufacturer, is allowed to go higher. Since some users may choose to operate the power supply at a case temperature higher than 90 °C, it then becomes important to know the temperature rise of the hottest semicon- ductors. This is covered in the specification table in the section entitled Thermal Characteristics. EMI CONSIDERATIONS The ADDC02803SC and ADDC02805SA have an integral differential- and common-mode EMI filter designed to meet all applicable requirements in MIL-STD-461D when the power converters are installed in a typical system setup (described below). The converters also contain transient protection circuitry that permit the units to survive short, high voltage transients across their input power leads. The purpose of this section is to describe the various MIL-STD-461D tests and the converters’ corresponding performance. Consult factory for additional information. The figures and tests referenced herein were obtained from measurements on the ADDC02805SA, a single 5 V dc output converter. Since the construction and topology of the 3.3 V output converter is almost identical to the 5 V dc output con- verter, and the component values of the EMI differential- and common-mode filter in the 3.3 V output converter are identical to the 5 V output converter, the text references these figures and tests as typical of the ADDC02803SC converter as well. Electromagnetic interference (EMI) is governed by MIL-STD-461D, which establishes design requirements, and MIL-STD-462D, which defines test methods. EMI requirements are categorized as follows (xxx designates a three digit number):
- CExxx: conducted emissions (EMI produced internal to the power supply which is conducted externally through its input power leads)
- CSxxx: conducted susceptibility (EMI produced external to the power supply which is conducted internally through the input power leads and may interfere with the supply’s operation)
- RExxx: radiated emissions (EMI produced internal to the power supply which is radiated into the surrounding space)
- RSxxx: radiated susceptibility (EMI produced external to the power supply which radiates into or through the power supply and may interfere with its proper operation) It should be noted that there are several areas of ambiguity with respect to CE102 measurements that may concern the systems engineer. One area of ambiguity in this measurement is the nature of the load. If it is constant, the ripple voltage on the converter’s input leads is due only to the operation of the con- verter. If, on the other hand, the load is changing over time, this variation causes an additional input current and voltage ripple to be drawn at the same frequency. If the frequency is high enough, the converter’s filter will help attenuate this se cond source of ripple, but if it is below approximately 100 kHz, it will not. The system may then not meet the CE102 requirement, even though the converter is not the source of the EMI. If this is the case, additional capacitance may be needed across the load or across the input to the converter. Another ambiguity in the CE102 measurement concerns common- mode voltage. If the load is left unconnected from the ground plane (even though the case is grounded), the common-mode ripple voltages will be smaller than if the load is grounded. The test specifications do not state which procedure should be used. However, in neither case (load grounded or floating) will the typical EMI test setup described below be exactly representative of the final system configuration EMI test. For the following reasons, the same is true if separately packaged EMI filters are used. In almost all systems the output ground of the converter is ulti- mately connected to the input ground of the system. The para- sitic capacitances and inductances in this connection will affect the common-mode voltage and the CE102 measurement. In addition, the inductive impedance of this ground connection can cause resonances, thereby affecting the performance of the common-mode filter in the power supply. In response to these ambiguities, the Analog Devices’ converter has been tested for CE102 under a constant load and with the output ground floating. While these measurements are a good indication of how the converter will operate in the final system configuration, the user should confirm CE102 testing in the final system configuration. CE101: This test measures emissions on the input leads in the frequency range between 30 Hz and 10 kHz. The intent of this requirement is to ensure that the dc/dc converter does not cor- rupt the power quality (allowable voltage distortion) on the power buses present on the platform. There are several CE101 limit curves in MIL-STD-461D. The most stringent one app- licable for the converter is the one for submarine applications. Figure 19 shows that the converter easily meets this requirement (the return line measurement is similar). The components at
60 Hz and its harmonics are a result of ripple in the output of
the power source used to supply the converter.
REV. A –15– Circuit Setup for EMI Test Figure 23 shows a schematic of the test setup used for the EMI measurements discussed above. The output of the converter is connected to a resistive load designed to draw full power. There is a 0.1 mF capacitor placed across this resistor that typifies by- pass capacitance normally used in this application. At the input of the converter there are two differential capacitors (the larger one having a series resistance) and two small common-mode capacitors connected to case ground. The case itself was con- nected to the metal ground plane in the test chamber. For the RE102 test, a metal screen box was used to cover both the con- verter and its load (but not the two meters of input power lead cables). This box was also electrically connected to the metal ground plane. With regard to the components added to the input power lines, the 100 mF capacitor with its 1 W series resistance is required to achieve system stability when the unit is powered through the LISNs, as the MIL-STD-461D standard requires. These LISNs have a series inductance of 50 mH at low frequencies, giving a total differential inductance of 100 mH. As explained earlier in the System Instability section, such a large series source inductance will cause an instability as it interacts with the converter’s negative incremental input resistance unless some corrective action is taken. The 100 mF capacitor and 1 W resis- tor provide the stabilization required. It should be noted that the values of these stabilization components are appropriate for a single converter load. If the system makes use of several converters, the values of the components will need to be slightly changed, but not such that they are repeated for every converter. It should also be noted that most system appli- cations will not have a source inductance as large as the 100 mH built into the LISNs. For those systems, a much smaller input capacitor could be used. Increasing Margin Between Specification Limit and Measured Results With regard to the 2 mF differential-mode capacitor and the two 82 nF common-mode capacitors, these components were in- cluded in the test setup to augment the performance of the power supply’s internal EMI filter. The values were chosen to achieve the results shown in Figures 20 and 22. To increase the margin between the specification limits and the measured emis- sions, larger external component values could be used. To do this it is useful to know that most of the emissions below
10 MHz, whether conducted or radiated, are due to differential-
mode currents flowing in the input power leads. To make the emissions in this frequency range smaller, the differential ca- pacitor value should be increased above 2 mF. Conversely, most of the emissions above 10 MHz are due to common-mode cur- rents; to make them smaller the common-mode capacitors should be increased above the 82 nF value. In both cases it is important to minimize the parasitic inductance of the capaci- tors; the use of several smaller capacitors connected in parallel is one way to achieve this. Using larger valued capacitors than those shown in Figure 23 is a good solution if an additional 6 dB–10 dB of margin is de- sired. If, however, in an extremely sensitive application it is desired to increase the margin by 20 dB or more, it may be better to add both differential- and common-mode inductors to the external components to make a higher order filter. RELIABILITY CONSIDERATIONS MTBF (Mean Time Between Failure) is a commonly used reliability concept that applies to repairable items in which failed elements are replaced upon failure. The expression for MTBF is MTBF = T/r where: T = total operating time r = number of failures In lieu of actual field data, MTBF can be predicted per MIL-HDBK-217. MTBF, Failure Rate and Probability of Failure: A proper understanding of MTBF begins with its relationship to lambda (l), which is the failure rate. If a constant failure rate is assumed, then MTBF = 1/l, or l = 1/MTBF. If a power supply has an MTBF of 1,000,000 hours, this does not mean it will last 1,000,000 hours before it fails. Instead, the MTBF describes the failure rate. For 1,000,000 hours MTBF, the failure rate during any hour is 1/1,000,000, or 0.0001%. Thus, a power supply with an MTBF of 500,000 hours would have twice the failure rate (0.0002%) of one with 1,000,000 hours. What users should be interested in is the probability of a power supply not failing prior to some time t. Given the assumption of a constant failure rate, this probability is defined as R(t) = e±lt where R(t) is the probability of a device not failing prior to some time t. If we substitute l = 1/MTBF in the above formula, then the expression becomes R(t) = e MTBF This formula is the correct way to interpret the meaning of MTBF. If we assume t = MTBF = 1,000,000 hours, then the probability that a power supply will not fail prior to 1,000,000 hours of use is e–1, or 36.8%. This is quite different from saying the power supply will last 1,000,000 hours before it fails. The probability that the power supply will not fail prior to 50,000 hours of use is e –0.05, or 95%. For t = 10,000 hours, the probability of no fail- ure is e–0.01, or 99%. Temperature and Environmental Factors: Although the calculation of MTBF per MIL-HDBK-217 is a detailed process, there are two key variables that give the manufacturer signi- ficant leeway in predicting an MTBF rating. These two vari- ables are temperature and environmental factor. For users to properly compare MTBF numbers from two different manu- facturers, the environmental factor and the tem perature must be identical. Contact the factory for MTBF calculations for specific environmental factors and temperatures.
Figure 38. Fault Tolerant, Secondary Side Powered SYNC Drive Circuit
- Input to Output Isolation : With the use of the Isolink opto-
AUX pin (input referenced) to power the opto-coupler.
- Fault Tolerant: All outputs are capacitively coupled to ensure
thereby eliminating a potential single point failure.
- Radiated Emissions: C2 can be added to slow down the clock
edges (Tr and Tf) for reducing radiated emissions.
- Table: The following table shows the capacitor and resis-
REV. A–18– Screening Levels for ADDC02803SC/ADDC02805SA Screening Steps Industrial (KV) Ruggedized Industrial (TV) MIL-STD-883B/SMD (TV/QMLH) Pre-Cap Visual 100% MIL-STD-883, TM2017 Temp Cycle N/A N/A Constant Acceleration N/A N/A Fine Leak Guaranteed to Meet Guaranteed to Meet MIL-STD-883, TM1014 MIL-STD-883, TM1014 Compliant to MIL-PRF-38534Gross Leak Guaranteed to Meet Guaranteed to Meet MIL-STD-883, TM1014 MIL-STD-883, TM1014 Burn-In N/A MIL-STD-883, TM1015,
96 Hrs at +125°C Case
Final Electrical Test At +25 °C, Per Specification At +25 °C, Per Specification Table Table NOMINAL CASE DIMENSIONS IN INCHES AND (mm) (All tolerances – .005" [ – .13 mm] unless otherwise specified) 0.150 (3.81) 0.100 (2.54)
8 PLCS
0.200 (5.08) 0.150 (3.81) 0.200 (5.08) 0.390 6 0.010 (9.91 6 0.25) 0.800 6 0.010
2 PLCS
0.150 (3.81)
4 PLCS
0.149 (3.78) DIA TYP 0.300 (7.62) SQ 6 0.010 0.200 (5.08) 5 PLCS 0.250 (6.35) 1.500 6 0.010 (38.10 6 0.25) 0.040 6 0.003 (1.02 6 0.08) 0.090 6 0.010 (2.29 6 0.25) 2.745 6 0.010 (69.72 6 0.25) 1.800 (45.72) TYP 2.100 6 0.010 (53.34 6 0.25) NOTES 1. The final product weight is 85 grams maximum. 2. The package base material is made of molybdenum and is nominally 40 mils (1.02 mm) thick. The “runout” is less than 2 mils per inch (0.02 mm per cm). 3. The high current pins (10–17) are 40 mil (1.02 mm) diameter; are 99.8% copper; and are plated with gold over nickel. 4. The signal carrying pins (1–9) are 18 mil (0.46 mm) diam- eter; are Kovar; and are plated with gold over nickel. 5. All pins are a minimum length of 0.740 inches (18.80 mm) when the product is shipped. The pins are typically bent up or down and cut shorter for proper connection into the user’s system. 6. All pin-to-sidewall spacings are guaranteed for a minimum of 500 V dc breakdown at standard air pressure. 7. The case outline was originally designed using the inch- pound units of measurement. In the event of conflict be- tween the metric and inch-pound units, the inch-pound shall take precedence. C3056a–4–10/98PRINTED IN U.S.A.