Product # MQME-270-R

Phone 1-888-567-9596

www.synqor.com

Doc.# 005-0006166 Rev. E

05/31/2016

Page 6

MQME-270-R

Technical Specification

BASIC OPERATION AND FEATURES

The MQME-270-R 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-270-R 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-270-R

EMI filter is designed to pass all of 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.

The filter is also designed to pass the waveform types and applications

specified in RTCA/DO-160E/F/G Section 22 (Lightning Induced

Transient Susceptibility) to Level 4 (some waveforms / applications

require external transient suppression circuitry). The Section 22

Compliance Matrix Table lists these waveforms and applications

and describes the setup used to pass them.

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-270-R 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.

REVERSE POLARITY PROTECTION: The MQME-270-R EMI filter

has a series-connected diode. This diode blocks reverse current

flow if the filter's input voltage is mistakenly connected with the

wrong polarity. The anti-parallel diode, working with the reverse

polarity diode, 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 reverse polarity diode also preforms 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, thediode allows the total bulk

capacitor (located both within and external to the filter) to better

hold up the output voltage during these transients.