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MQHE-28E Datasheet(PDF) 6 Page - SynQor Worldwide Headquarters |
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MQHE-28E Datasheet(HTML) 6 Page - SynQor Worldwide Headquarters |
6 / 18 page Product # MQME-28E-T6 Phone 1-888-567-9596 www.synqor.com Doc.# 005-0006011 Rev. C 05/27/16 Page 6 Current: 20A MQME-28E-T6 Technical Specification BASIC OPERATION AND FEATURES The MQME-28E-T6 is a multi-stage differential-mode and common- mode passive EMI filter designed to interface a power source with one or more SynQor DC/DC converters (or other loads that create EMI). Each stage of this filter is well damped to avoid resonances and oscillations, and only X7R multi-layer ceramic capacitors are used. Figure 1 shows the typical differential and common-mode attenuation provided by this filter when the source impedance is 50W to chassis ground on each input line. The MQME-28E-T6 EMI filter includes a large bulk capacitor (also X7R) with a series damping resistor to correct for the unstabilizing effect of a converter’s negative input resistance. A white paper discussing this negative input resistance and the need for corrective damping can be found on the SynQor website (see Input System Instability application note). Figure 2 shows the magnitude of the filter’s output impedance when the filter input is connected to a stiff voltage source. When used with SynQor’s DC/DC converters, the MQME-28E-T6 EMI filter is designed to pass all the relevant MIL-STD-461C/D/ E/F requirements to their most stringent limits. The MIL-STD-461 Compliance Matrix Table lists these requirements and describes the setup used to pass them. Figures 3 - 6 show results from selected conductive and radiated emissions tests. TRANSIENT SUPPRESSION: The input voltage surge and spike compliance matrix displays the worst case requirements listed in various 28V Military (Vehicle and Aircraft) and Civil Aircraft standards. The MQME-28E-T6 EMI filter is designed to handle all of the short duration voltage spike requirements of these standards (with certain assumptions regarding DEF-STAN 61-5). Some of the long duration voltage surge requirements remain within the 50V maximum transient rating of a SynQor MQFL-28 DC/DC converter. The others require the transient suppression circuitry of the MQME-28E-T6 EMI filter to protect the converter from an over-voltage condition. If MQFL-28E or MQFL-28VE converters are used, voltage surges as high as 80V can be tolerated without the need for this transient suppression circuitry. The MQME-28E-T6 EMI filter is also designed to pass the waveform types and applications specified in RTCA/DO-160E Section 22 (Lightning Induced Transient Susceptibility) to Level 4. The Section 22 Compliance Matrix Table lists these waveforms and applications and describes the setup used to pass them. REVERSE POLARITY PROTECTION: The MQME-28E-T6 EMI filter has a series-connected MOSFET that is controlled to function as a diode, but with a very small forward voltage drop (≤ 4 mW x Iout). This “Synchronous Rectifier” blocks reverse current flow if the filter’s input voltage is mistakenly connected with the wrong polarity. The anti-parallel diode, working with the synchronous rectifier, ensures that the filter’s output voltage goes only slightly negative during this time, and therefore satisfying the minimum input voltage specifications of SynQor’s MQFL converters. The synchronous rectifier also performs a useful function during negative polarity spikes and surges, and during brief power interrupts. Since it stops current from flowing negatively through the EMI filter back toward the source, the synchronous rectifier allows the total bulk capacitor (located both within and external to the filter) to better hold up the output voltage during these transients. ENABLE: The MQME-28E-T6 filter has enable pass-through circuitry that bridges an enable signal across the filter’s common- mode impedance. The ENABLE INPUT pin (pin 4) is referenced with respect to the filter’s INPUT RETURN (pins 5 and 6). The ENABLE OUTPUT pin (pin 9) is referenced with respect to the filter’s OUTPUT RETURN (pin 7). The INPUT RETURN and OUTPUT RETURN may have a different voltage due to common- mode noise and transients. NOTE: During the time that the MQME-28E-T6 filter is in its Soft- Start mode the ENABLE OUTPUT will be held at a logic low. This is done so that all of the filter’s loads can be disabled by this signal during the Soft-Start period. Once the Soft-Start is completed, ENABLE OUTPUT will follow ENABLE INPUT. Figure A shows the equivalent circuit looking into ENABLE INPUT. The ENABLE INPUT pin must be pulled low to turn an MQFL converter off. It may be left open-circuit to turn the converter on. Figure B shows the equivalent circuit looking into ENABLE OUTPUT. The n-channel MOSFET in this circuit turns on when power is applied to the filter and ENABLE INPUT is low. Otherwise, the MOSFET is off. ENABLE OUTPUT is capable of driving the ENABLE INPUTs of up to 15 MQFL converters. If the enable pass-through circuit is not being used, the ENABLE INPUT pin may be left open or connected to the INPUT RETURN pins. The ENABLE OUTPUT pin may be left open or connected to the OUTPUT RETURN pins. SOFT-START: The MQME-28E-T6 filter incorporates Soft-Start circuitry to limit the amount of current drawn from the power source by the charging of large bulk capacitors at the filter’s output. 2N3904 1N4148 250K 125K 82K 5.6V TO ENABLE CIRCUITRY PIN 4 (ENABLE INPUT) PINS 5 AND 6 (INPUT RETURN) 33nF Figure A: Equivalent circuit looking into the ENABLE INPUT pin with respect to the INPUT RETURN pin. Once the input voltage exceeds the turn-on threshold value, the Soft-Start circuitry controls the filter’s output current to be approximately 1.6A. This mode of operation continues until the filter’s output voltage reaches the input voltage, at which time the filter is able to deliver its rated output current. If after the Soft- Start duration period the filter’s output has not risen to the input voltage, then the filter will disconnect the output from the input, wait for a time equal to the Soft-Start recycle period, and initiate a new Soft-Start. Since, during Soft-Start, the filter will deliver only 1.6A to its output, it is important to limit the load current so that the total bulk capacitance can be fully charged before the Soft-Start duration period is over. To facilitate this, the filter’s ENABLE OUTPUT pin is held low during the Soft-Start mode. This signal can therefore be used to disable the filter’s loads during this time. Once the Soft- Start mode is completed, ENABLE OUTPUT will follow ENABLE INPUT. OUTPUT POWER LIMIT: The MQME-28E-T6 filter has an output power limit feature to protect against a short circuit at its output pins. This limit is disabled whenever the output voltage is rising so that it will not be encountered when charging output capacitance. When the output power exceeds ~450W and its output voltage is decreasing however, this feature will turn the filter off and reinstitute a soft-start cycle in 500ms. Figure C shows the output power limit threshold as a function of output voltage. STANDBY: The MQME-28E-T6 filter has standby circuitry that minimizes the power drawn from the filter’s input power source when the standby feature is activated. It does this in two ways. First, the output of the filter is disconnected from the input so that there will be no power drawn by downstream converters or other loads. Second, the active circuitry within the filter is placed into a reduced power consumption mode. The net result is a current draw of only about 2mA from a 28V input power source. Figure D shows the equivalent circuit looking into the STANDBY pin (pin 8). This pin is referenced with respect to the filter’s OUTPUT RETURN pin (pin 7). It should be pulled low to have the filter operate in its normal mode. If the pin is instead left open-circuit and pulled high by its internal circuitry, the standby feature will be activated. Application Note: A typical application would place the MQME filter close to the input of the DC/DC converter, with the cases of the filter and the converter connected together through a ground plane. Both cases are electrically conductive, so connection to the cases can be made with the fasteners used to secure the device. Do not connect the outputs of multiple MQME-28E-T6 filters in parallel. Connecting filters in this manner may result in slightly unequal currents to flow in the positive and return paths of each filter. These unequal currents may cause the internal common- mode chokes to saturate and thus cause degraded common-mode rejection performance. PIN 9 (ENABLE OUTPUT) PIN 7 (OUTPUT RETURN) 0.01 µF Figure B: Equivalent circuit looking into the ENABLE OUTPUT pin with respect to the OUTPUT RETURN pin. 5V 50k 0.01 µF To Standby Circuitry PIN 8 (Standby) PIN 7 (Output Return) Figure D: Equivalent circuit looking into the STANDBY pin with respect to the OUTPUT RETURN pin. Figure C: Output Power Limit. 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70 Output Voltage (V) 0 100 200 300 400 500 600 700 800 Current Power |
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