APPLICATION NOTE | AN:022 MIL EMI and Transient Solutions Written by: Jeffrey Ham Principal Product Line Engineer Contributions by: Robert Pauplis Senior Principal Product Line Engineer; et al. December 2007 ContentsPage Introduction1 MIL-STD-4611 Basics of EMI 2 Transient Immunity 7 Conclusion16 Introduction 28 Volt defense applications must meet a number of noise and power related standards such as MIL-STD-461, MIL-STD-704, and MIL-STD-1275. To complicate matters, there are a number of revisions to these standards, any of which may be enforced by the application. Additionally, within each standard are subsections that apply as dictated by the end installation. This Application Note will review these standards and offer means of achieving compliance when using Vicor’s MIL-COTS VI Chips® (MP028F036M12AL and MV036FxxxMxxx series). MIL-STD-461 The latest revision of this standard is MIL-STD-461E. It is a comprehensive document addressing Conducted Emissions, Conducted Susceptibility, Radiated Emissions, and Radiated Susceptibility. Emission refers to the noise a device generates as it impacts the source to which it is connected. Susceptibility is the vulnerability of a system to incoming noise. Table 1 shows the requirements for each substandard; and Table 2 illustrates the sections related to each of these and the applicability based upon installed platform. As can be observed from Table 2, not all sections are universally required. Hence, most power conversion suppliers focus on achieving compliance to the subset where all installations are affected and in particular to the conducted sections rather than the radiated. These standards are CE102, CS101, CS114, and CS116. Frequently, manufacturers will also reference CE101, as the switching frequency of most DC-DC converters are well beyond the frequency band of interest. Conducted emission and susceptibility requirements are quoted (and not radiated requirements) because radiated sections are significantly dependent upon the physical layout, external output circuitry and enclosure in which the power supply resides. A valid filter design and good PCB layout mean conducted requirements are easily met. There is not much difference between revision E and the earlier revision D; in fact, of sections CE101, CE102, CS101, CS114, and CS116 only CS101 and CS114 are different. The extent of the differences are: CS101 - No change up to 5 kHz; above 5 kHz: 461D: Required level drops 20 dB / decade to 50 kHz 461E: Required level drops 20 dB / decade to 150 kHz CS114 - No change up to 30 MHz; above 30 MHz: 461D: Required level drops 10 dB / decade to 400 MHz 461E: Required level drops 10 dB / decade to 200 MHz AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 1 Table 1. Requirement Summary of MIL-STD-461E Requirements Description CE101 Conducted Emissions, Power Leads, 30 Hz to 10 kHz CE102 Conducted Emissions, Power Leads, 10 kHz to 10 MHz CE106 Conducted Emissions, Antenna Terminal, 10 kHz to 40 GHz CS101 Conducted Susceptibility, Power Leads, 30 Hz to 150 kHz CS103 Conducted Susceptibility, Antenna Port, Intermodulation, 15 kHz to 10 GHz CS104 Conducted Susceptibility, Antenna Port, Rejection of Undesired Signals, 30 Hz to 20 GHz CS105 Conducted Susceptibility, Antenna Port, Cross-Modulation, 30 Hz to 20 GHz CS109 Conducted Susceptibility, Structure Current, 60 Hz to 100 kHz CS114 Conducted Susceptibility, Bulk Cable Injection, 10 kHz to 200 MHz CS115 Conducted Susceptibility, Bulk Cable Injection, Impulse Excitation CS116 Conducted Susceptibility, Damped Sinusoidal Transients, Cables and Power Leads, 10 kHz to 100 MHz RE101 Radiated Emissions, Magnetic Field, 30 Hz to 100 kHz RE102 Radiated Emissions, Electric Field, 10 kHz to 18 GHz RE103 Radiated Emissions, Antenna Spurious and Harmonic Outputs, 10 kHz to 40 GHz RS101 Radiated Susceptibility, Magnetic Field, 30 Hz to 100 kHz RS103 Radiated Susceptibility, Electric Field, 2 MHz to 40 GHz RS105 Radiated Susceptibility, Transient Electromagnetic Field Now we have introduced the standard, how do we gain compliance? What follows is a general guide for EMI filter design. We will focus on CE102 for our discussion. Basics of EMI EMI measurement are separated into two parts: n Conducted n Radiated Conducted measurements are measurements of either voltages or currents flowing in the leads of the device under test (as dictated by the standard). Common mode conducted noise current is the unidirectional (in phase) component in both the positive and negative inputs to the module. This current circulates from the converter via the power input leads to the DC source and returns to the converter via the output lead connections. This represents a potentially large loop cross-sectional area that, if not effectively controlled, can generate magnetic fields. Common mode noise is a function of the dv/dt across the main switch in the converter and the effective input to output capacitance of the converter. Differential mode conducted noise current is the component of current, at the input power terminal, which is opposite in direction or phase with respect to each other. For our purposes we will concentrate on MIL-STD-461, CE102 that is a voltage measurement into 50 ohms. E-Field radiated emissions are due to conducted currents through a suitable antenna such as the power leads of the device under test. If we can greatly reduce the conducted emissions then we will reduce the radiated emissions as well. The enclosure of the device under test, lead geometry, and other devices running within the device under test will affect the emissions. Radiated emissions due to B-Fields are best addressed by shielding with a suitable material and proper layout. AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 2 Table 2. Equipment and Subsystems installed in, on, or launched from the following platforms or installations: Section Requirement Applicability Requirement Applicability L A S S S Aircraft, Navy L A A L A A L A A A L A A L A A A A A L A A L L L A L A L A S S S A A A A L Aircraft, Air Force A L A S S S A A A A L A Space Systems, Including Launch Vehicles A L A S S S A A A A L A Ground, Army A L A S S S A A A A L L A Ground, Navy A L A S S S A A A A L A A Ground, Air Force A L A S S S A A A A L Legend: A L S RS105 A A L RS103 A L A RS101 Aircraft, Army, Including Flight Line A L RE103 S RE102 S RE101 S S CS116 S A CS115 S L CS114 A A CS109 CS105 CS104 CS103 CS101 CE102 L A Surface Ships CS106 CE101 A Submarines L A Applicable Limited as specified in the individual sections of this standard Procuring activity must specify in procurement documentation A defined test setup, known source impedance, and limits to which we can compare results are needed to get repeatable results. The standard test configuration is shown in Figure 1. Figure 1. MIL-STD-461 Test Setup Access Panel Power Source Interconnecting Cable Bond strap Non-Conductive Standoff EUT 2 cm 10 cm LISNs Ground Plane 5 cm 2m 80-90 cm The known impedance is realized with the use of Line Impedance Stabilization Networks (LISN) terminated into 50 Ω (internal to the measurement device). One LISN per power lead is needed. This is illustrated in Figures 1 & 2. AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 3 Figure 2. LISN Schematic and Impedance Graph Figure 3 shows the spec limits. It is beneficial to translate the limits to millivolts in addition to the standard dBμV. Figure 3. From the limits shown in Figure 3 for 28 V systems, we can see that at 500 kHz and above, the limit is 1Millivolt into 50 Ω. Given the limits, we will need to understand the source of the noise to determine the amount of attenuation required to stay below the limits. It is critical to understand the properties of the noise source in order to design a good filter. AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 4 Since in most cases the noise character of a device is unknown, the most effective solution is to have the device in hand prior to the development of a filter. The noise source can then be characterized through experimentation and, once characterized, a model can be generated. A good series of noise voltage measurements are: n n n n n Input to ground – open circuit. Input to ground – 100-ohm shunt termination. (With DC blocking cap) Input to ground – 10-ohm shunt termination. (With DC blocking cap) Input to ground – 1-ohm shunt termination. (With DC blocking cap) Measurement of the short circuit common mode current input-output. Let's assume the noise voltage measurements are: n n n n n Input to ground – open circuit. Input to ground – 100 ohm Input to ground – 10 ohm Input to ground – 1 ohm Short circuit (50nH) current input-output. 10 V P-P 4 V P-P 580 mV P-P 280 mV P-P 290 mA The equivalent circuit (model) would be most nearly a 10 V source as found from the open circuit test, with a series resistance of about 35 ohms. (10 V from the open circuit test and 0.28 A from the 1 ohm test) Let's now investigate adding "Y" capacitance (from Line to Ground). This 4,700 pF device has an impedance of ~13 Ω at 2.3 MHz (an assumed frequency of the ring wave measured in the 1 Ω termination test.) “Repeat” the measurement to observe the amplitude of the waveform. Let's also assume that the result of this measurement yields 1.3 V. We now need to check our results: A 10 V noise source with a series impedance of about 35 ohms is the model for the source. The “Y” capacitor has an impedance of 13 ohms at 2.7 MHz. Solving for the voltage across the capacitor yields 2.7 V. The "measured" value across the 4,700 pF capacitor is 1.3 V Although this looks like a huge difference in percentage, we are only off -6.3 db from the calculations. The good news is the error is in the right direction. So what do we know? If we measure the conducted emissions using a LISN we would see a value of only slightly less than 1.3V. Our source impedance is still relatively low with respect to 50 ohms. i.e. 1.3 Vocv, Isc 0.29 A = 4.5 ohms. Our target voltage measurement value is 1 mV, we only need 63 db of additional attenuation. Is it practical to continue to add shunt capacitance or impedances? No, even if we could add as much shunt capacitance as we wanted the entire impedance, given an Isc current of 290 mA, would require the total shunt impedance <3.4 milliohms. This dictates that a practical filter must be constructed of a cascade of shunt and series devices forming an AC voltage divider. This is illustrated in Figure 4. For a good design we need to understand the impedance of every part and the potential interaction. It is good practice to keep the "Q" of the inductors and the ESR AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 5 Figure 4. Multistage Filter for MIL-STD-461 compliance R2 L3 C1 C3 C4 C6 R1 C2 L1 L4 C5 L2 Series impedance for CM+DM Shunt impedance for CM Shunt impedance for DM of the capacitors low for good attenuation without creating a resonance or as it is sometimes called “peaking”. Layout of the filter is very important to avoid inadvertent parasitic coupling. For the example filter above, parasitic capacitance from input to output could easily be 1pF, which is about 60K ohms at 2.7 Mhz. If there were no shunt impedance looking back into the filter this would produce over 1mV at the LISN, putting us above the limit on its own. The filter impedance (looking into the input) as well as additional “Y” capacitance either real or parasitic near C1 helps mitigate the effects of this parasitic. It is important to note that inductive coupling will have the same effect. Good layout practice is imperative so as to prevent input to output and stage to stage coupling. Having a filter precede a power component has the added benefit of providing attenuation to transient fluctuations in the source voltage. Short duration, high dv/ dt, events have little energy associated and the inductance and capacitance present in a filter is sometimes enough to integrate this energy by reducing the peak, and expanding the time as it appears at the output of the filter. Unfortunately, the power supply to the application (as defined by the standard) can frequently exceed the capacity of the input filter to mitigate these power excursions; and so additional circuitry may be needed to transform them in such a way as to not affect the power device. AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 6 Transient Immunity MIL-STD-704 and MIL-STD-1275 refer to aircraft and ground-based systems that describe the anticipated power quality of those systems, and the levels a device must meet or exceed in order to perform satisfactorily in the anticipated application. Other standards may be required but are not covered in this paper. Tables 3-7 below give a summary of the most current revisions of 28 Vdc system requirements. Table 3. 28 V Transient Standard Summary Specification RTCA DO-160E Section 16 Power input Airborne Equipment Category Z DEF STAN 61-5, Part 6 28 Vdc Electrical Systems in Military Vehicles Mil-Std-1275D 28 Vdc Electrical Systems in Mil Vehicles AIRBUS BD0100.1.8 Electrical Installation Conventional DC Network Test Description Vstart Vdc Time Sec Vsurge Vdc Tr ms Duration msec Tf ms Vnom Vdc Time sec Remarks Interval sec Normal Surge Par. 16.6.1.4 28 300 50 1 50 1 28 5 Repeat 3 times 5 28 300 12 1 30 1 28 5 Repeat 3 times 5 Abnormal Surge Par. 16.6.2.4 28 300 80 ns 100 ns 28 ns Repeat 3 times 1 28 300 48 ns 1,000 ns 28 ns Repeat 3 times 10 Import Surge Generator Plus Battery 26.4 300 40 ns 50 50 26.4 1 Repeat 5 times 1 26.4 300 20 ns 500 500 26.4 1 Repeat 5 times 1 26.4 300 100 ns 50 150 26.4 1 Repeat 5 times 1 26.4 300 15.4 ns 500 150 26.4 1 Repeat 5 times 1 Normal Import Surge Generator Plus Battery 28 300 40 1 50 1 28 ns Repeat 5 times 1 Generator Only 28 300 100 1 50 1 28 ns Repeat 5 times 1 27.5 300 40 ns 30 ns 27.5 5 5 5 Import Surge Generator Only Voltage Surge Normal Trans. Test 3.1 Test 3.2 Test 3.3 Test 3.4 27.5 300 17 ns 15 ns 27.5 5 27.5 300 39 ns 50 ns 27.5 5 5 Repeat each test 3 times 27.5 300 19.5 ns 30 ns 27.5 5 5 27.5 300 37 ns 100 ns 27.5 5 27.5 300 21 ns 50 ns 27.5 5 5 27.5 300 35 ns 200 ns 27.5 5 5 27.5 300 23.5 ns 100 ns 27.5 5 5 5 ns = not specified AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 7 Table 4. 28 V Transient Standard Summary Specification AIRBUS ABD0100.1.8 Electrical Installation Conventional DC Network Test Description Vstart Vdc Time Sec Vsurge Vdc Tr ms Duration msec Tf ms Vnom Vdc Time sec Test 4.1 27.5 300 46 Test 4.2 27.5 300 38 27.5 300 Test 2.1 27.5 Test 2.2 Remarks Interval sec ns 100 ns 27.5 5 ns 1,000 ns 27.5 5 Repeat 3 times 5 0 ns 5,000 ns 27.5 5 5 300 36 ns 100 ns 27.5 5 5 27.5 300 35 ns 200 ns 27.5 5 Test 2.3 27.5 300 34 ns 300 ns 27.5 5 Test 2.4 27.5 300 18.5 ns 5,000 ns 27.5 5 5 Test 3.1 27.5 300 36 ns 1,000 ns 27.5 5 5 Test 3.2 27.5 300 33 ns 3,000 ns 27.5 5 Test 3.3 27.5 300 0 ns 5,000 ns 27.5 5 AA 29 300 50 <1 12.5 <1 29 BB 29 300 50 <1 12.5 70 29 CC 29 300 40 <1 45 <1 29 Voltage Surge Abnormal Trans. 5 Voltage Surge Normal Trans. AIRBUS ABD0100.1.8 Electrical Installation NBPT* DC Network *No Break Power Transfer Repeat 3 times 5 5 Voltage Surge Abnormal Trans. Repeat 3 times 5 5 Normal Voltage Trans. Overvoltage Mil-Std-704F and Mil-HDBK-704 Part 8 DD 29 300 40 <1 45 37.5 29 EE 29 300 50 <1 10 <1 29 FF 22 300 50 <1 12.5 <1 22 GG 22 300 50 <1 12.5 95 22 HH 22 300 40 <1 45 <1 22 AN:022 Repeat 3 times .0005 ns = not specified vicorpower.com Applications Engineering: 800 927.9474 Page 8 Table 5. 28 V Transient Standard Summary Specification Test Description Vstart Vdc Time Sec Vsurge Vdc Tr ms Duration msec Tf ms Vnom Vdc II 22 300 40 <1 45 62.5 22 JJ 22 300 50 <1 10 <1 22 KK 29 300 18 <1 15 <1 29 LL 29 300 18 <1 15 234 29 MM 29 300 18 <1 10 <1 29 NN 22 300 18 <1 15 <1 22 OO 22 300 18 <1 15 85 22 PP 22 300 18 <1 10 <1 22 29 300 18 <1 10 <1 29 50 <1 12.5 70 29 18 <1 10 <1 22 50 <1 12.5 62.5 22 18 30 45 Vdc 2.5 28.5 Time sec Remarks Interval sec Repeat 3 times .0005 Repeat 3 times .0005 Repeat 3 times .0005 Normal Voltage Trans. Overvoltage Undervoltage Mil-Std-704F and Mil-HDBK-704 Part 8 (cont.) Combined Transient QQ RR Repetitive Normal Voltage Trans. then 22 300 then 28.5 AN:022 .0025 vicorpower.com <.001 Repeat 5 times <.001 Repeat 5 times Continuous for 30 min. Applications Engineering: 800 927.9474 .0005 Page 9 Table 6. 28 V Transient Standard Summary Specification Test Description Vstart Vdc Time Sec Vsurge Vdc Tr ms Duration msec Tf ms Vnom Vdc AAA 29 300 50 <1 50 <1 29 BBB 29 300 50 <1 50 15 45 Time sec Remarks Interval sec Repeat 3 times .5 Abnormal Voltage Trans. Overvoltage Mil-Std-704F and Mil-HDBK-704 Part 8 (cont.) then 45 decreasing 30 40 then 40 decreasing 60 35 then 35 decreasing 4,850 30 then 30 decreasing 1,000 29 CCC 29 300 50 <1 50 <1 29 DDD 22 300 50 <1 50 <1 22 EEE 22 300 50 <1 50 15 45 FFF then 45 decreasing 30 40 then 40 decreasing 60 35 then 35 decreasing 4,850 30 then 30 decreasing 8,000 22 22 300 50 <1 50 <1 22 GGG 29 300 7 <1 50 <1 29 HHH 29 300 7 <1 50 15 12 then 12 30 increasing na 17 then 17 60 increasing na 22 Undervoltage then 22 4,850 increasing na 28 then 28 1,000 increasing na 29 then 29 AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 10 Table 7. 28 V Transient Standard Summary Specification Test Description Vstart Vdc Time Sec Vsurge Vdc Tr ms Duration msec Tf ms Vnom Vdc Time sec Remarks Interval sec III 29 300 7 <1 50 <1 29 <1 Repeat 3 times .5 JJJ 22 300 7 <1 50 <1 22 <1 22 300 7 <1 Repeat 3 times .5 Abnormal Voltage Trans. Undervoltage KKK LLL 50 15 12 then 12 increasing 30 17 then 17 increasing 60 22 22 300 7 <1 50 <1 22 29 300 7 <1 10 <1 50 50 <1 50 15 45 Combined Trans. Mil-Std-704F and Mil-HDBK-704 Part 8 (cont.) MMM NNN then 45 decreasing 30 40 then 40 decreasing 60 35 then 35 decreasing 4,850 30 then 30 decreasing 1 29 then 29 10 <1 50 22 300 7 <1 50 <1 50 15 45 then 45 decreasing 30 40 then 40 decreasing 60 35 then 35 decreasing 4,850 30 then 30 decreasing 8,000 22 then 22 AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 11 As with MIL-STD-461 there are earlier revisions of 704 and 1275 that may be required depending upon the installation. Be certain you know which one is being imposed because the limits can vary greatly. MIL-STD-704F is relatively easy to meet. The tables 8-10 below summarize the important variations between the revisions of 704. Table 8. 28 Vdc Steady State NORMAL (V) ABNORMAL (V) EMERGENCY (V) Cat. A 25–28.5 23.5–30 17–24 Cat. B 24–28.5 22.5–30 16–24 Cat. C 23–28.5 21.5–30 15–24 MIL-STD-704C 22–29 20–31.5 16–30 MIL-STD-704D 22–29 20–31.5 16–29 MIL-STD-704E 22–29 20–31.5 18–29 MIL-STD-704F 22–29 20–31.5 16–29 704 Revision Summary MIL-STD-704A The Surge differences are: 28 Vdc Surges Table 9. Normal Operation 704 Revision Summary High Transients MIL-STD-704A Abnormal Operation Low Transients High Transients Low Transients Voltage (V) Time Voltage (V) Time Voltage (V) Time Voltage (V) Time Cat. A 70 20 mS 10 50 mS 80 50 mS 0 7S Cat. B 70 20 mS 8 50 mS 80 50 mS 0 7S 70 20 mS 7 50 mS 80 50 mS 0 7S MIL-STD-704C Cat. C 50 12.5 mS 18 15 mS 50 45 mS 0 7S MIL-STD-704D 50 12.5 mS 18 15 mS 50 45 mS 0 7S MIL-STD-704E 50 12.5 mS 18 15 mS 50 50 mS 0 7S MIL-STD-704F 50 12.5 mS 18 15 mS 50 50 mS 0 7S 28 Vdc Spikes Table 10. High Transients 704 Revision Summary MIL-STD-704A Low Transients Voltage (V) Time Voltage (V) Time Cat. A 600 50 µs -600 50 µs Cat. B 600 50 µs -600 50 µs Cat. C 600 50 µs -600 50 µs MIL-STD-704C N/A MIL-STD-704D Spikes less than 50 µS are controlled by MIL-E-6051 MIL-STD-704E N/A MIL-STD-704F N/A AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 12 As can be seen from Tables 8-10, 704 F is readily met if the power device has a normal input range of 16 -50 Vdc - no special precautions or circuitry is needed. The Vicor M-PRM Model MP028F036M12AL has this input range, allowing for direct compliance to this standard. If 704 A is required to be met, the MP028F036M12AL needs additional protection usually an input shunt Transorb to clamp the spike to a reasonable level, followed by an active clamp circuit using FETs to reduce the voltage to the output to the maximum level the DC device can tolerate. Figure 5 below illustrates the concept. Figure 5. Example Clamp Circuit U3 Q1 R6 0.03Ω U4 D5 D6 R5 1K ZENER R4 100 D3 1N418 R13 56k D1 1N4148 D7 ZENER D8 ZENER C6 3.3µF C4 R15 1nF 68 D4 1N4755 C7 220nF Q2 2N5550 C3 10uF R3 68 U1 UA555 Gnd Trg Out Rst Vcc Dis Thr CH + C5 1000uF R1 2.2k R2 5.1k R14 3.3k D2 C1 0.01uF U6 R16 3.6k R10 10K R9 100k C8 C2 1nF U5 U2 LM10C R11 2.7k 10nF R12 300 1 3+ 7 6 – 4 8 2 Q1 is the main clamping element and must be sized appropriately to handle the power dissipation needed during the 80 V (for 50 ms) abnormal requirement. Obviously if the downstream device can handle a higher voltage, less power must be dissipated in Q1. D6-8 are in this example 33 V 600 W devices. MIL-STD-1275D is a more severe requirement in that the Surge amplitude and duration is 100 Vdc for 50 ms. Tables 11-13 list the variations in revisions for MIL-STD-1275. As can be seen from these tables, with the exception of the 600 V spikes from 704 A, 1275D is more stringent. Therefore, if MIL-STD-1275D is met, 704 F is met and because the Transorb handles the 600 V spike, 704 A is also met. The circuit in Figure 5 could be built using discrete components, and an EMI filter could be designed using the methodology outlined earlier, but doing so requires iterations of build, test, evaluate, modify - dragging out the design phase of a project. To save time and ensure compliance, a ready-made product should be used, such as the Vicor M-FIAM7. AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 13 Table 11. 28 Vdc Steady State 1275 Revision Summary NORMAL (V) GEN ONLY (V) BATTERY ONLY (V) MIL-STD-1275A (AT) 25–30 23–33 20–27 MIL-STD-1275B 25–30 23–33 20–27 MIL-STD-1275C 25–30 23–33 20–27 MIL-STD-1275D 25–30 23–33 28 Vdc Surges Table 12. Fault Free Operation 1275 Revision Summary High Transients Single Fault Operation Low Transients High Transients Low Transients Voltage (V) Time Voltage (V) Time Voltage (V) Time Voltage (V) Time MIL-STD-1275A (AT) 40 50 mS 18.5 100 mS 100 50 mS 15 500 mS MIL-STD-1275B 40 50 mS 18.5 100 mS 100 50 mS 15 500 mS MIL-STD-1275C 40 50 mS 18 100 mS 100 50 mS 15 250 mS 28 Vdc Surges Normal Operating Mode High Transients MIL-STD-1275D Low Transients General Only Mode High Transients Low Transients Voltage (V) Time Voltage (V) Time Voltage (V) Time Voltage (V) Time 40 50 mS 18 500 mS 100 50 mS 15 500 mS Table 13. 28 Vdc Spikes Fault Free Operation 1275 Revision Summary High Transients MIL-STD-1275A (AT) Voltage (V) 250 Single Fault Operation Low Transients Time Voltage (V) 70 uS -250 High Transients Time Voltage (V) 70 uS 250 Low Transients Time Voltage (V) Time 70 uS -250 70 uS MIL-STD-1275B 250 70 uS -250 70 uS 250 70 uS -250 70 uS MIL-STD-1275C 250 70 uS -250 70 uS 250 70 uS -250 70 uS 28 Vdc Spikes Normal Operating Mode High Transients MIL-STD-1275D AN:022 Voltage (V) 250 Low Transients Time Voltage (V) 70 uS -250 vicorpower.com General Only Mode High Transients Time Voltage (V) 70 uS 250 Low Transients Time Voltage (V) Time 70 uS -250 70 uS Applications Engineering: 800 927.9474 Page 14 Figure 6 is plot of the transient protection behavior of the M-FIAM 7. Figure 6. The pre-filter Conducted Emission (CE102) plot for a raw PRM®/VTM® pair is shown in Figure 7. Figure 8 shows the same plot after the addition of the M-FIAM 7 with the measurement setup illustrated in Figure 9. Figure 7. Note the bulk of the energy needing to be attenuated is at and above the switching frequency of the PRM®/VTM® pair Figure 8. CE102 Plot after the addition of M-FIAM7 and Y capacitance AN:022 vicorpower.com Applications Engineering: 800 927.9474 Page 15 Conclusion Meeting the Compliance limits for EMI and Transient protection can be a daunting task. The steps involved in designing a filter from scratch, while doable, are tedious and time-consuming. Nevertheless this can be done if the steps outlined in this document are followed. A better method is to use a component such as the M-FIAM 7 that has been designed by the manufacturer of the power component. Doing so assures compatibility with the device and a huge reduction in the design effort. The Power Behind Performance Information furnished by Vicor is believed to be accurate and reliable. However, no responsibility is assumed by Vicor for its use. Vicor components are not designed to be used in applications, such as life support systems, wherein a failure or malfunction could result in injury or death. All sales are subject to Vicor’s Terms and Conditions of Sale, which are available upon request. Specifications are subject to change without notice. Rev 1.2 11/13 vicorpower.com Applications Engineering: 800 927.9474 Page 16