Product # MQME-270-P

Phone 1-888-567-9596

www.synqor.com

Doc.# 005-2ME027P Rev. 2

03/16/09

Page 6

MQME-270-P

Technical Specification

BASICOPERATIONANDFEATURES

TheMQME-270-Pisamulti-stagedifferential-modeandcommon-

mode passive EMI filter designed to interface a power source with

one or more SynQor DC/DC converters (or other loads that create

EMI).Eachstageofthisfilteriswelldampedtoavoidresonances

andoscillations,andonlyX7Rmulti-layerceramiccapacitorsare

used.Figure 1 shows the typical differential and common-mode

attenuation provided by this filter when the source impedance is

50Ω to chassis ground on each input line.

TheMQME-270-PEMIfilterincludesalargebulkcapacitor(also

X7R)withaseriesdampingresistortocorrectfortheunstabilizing

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

Instabilityapplicationnote).Figure2showsthemagnitudeofthe

filter’s output impedance when the filter input is connected to a stiff

voltage source.

The input voltage surge and spike compliance matrix shown on

Page 8 displays the worst case requirements listed in various

270VMilitary(VehicleandAircraft)andCivilAircraftstandards.

TheMQME-270-PEMIfilterisdesignedtohandlealloftheshort

durationvoltagespikerequirementsofthesestandards(withcertain

assumptionsregardingDEF-STAN61-5).Someofthelongduration

voltage surge requirements remain within the 50V maximum

transient rating of a SynQor MQFL-270 DC/DC converter. The

othersrequirethetransientsuppressioncircuitryofanMQME-270-T

EMI filter to protect the converter from an over-voltage condition. If

MQFL-270E or MQFL-270VE converters are used, voltage surges

ashighas80Vcanbetoleratedwithouttheneedforthistransient

suppression circuitry.

When used with SynQor’s DC/DC converters, the MQME-270-P

EMIfilterisdesignedtopassalloftherelevantMIL-STD-461C/D/E

requirements to their most stringent limits.The MIL-STD-461

ComplianceMatrixTableonPage7liststheserequirementsand

describesthesetupusedtopassthem.Figures3-6showresults

from selected conductive and radiated emissions tests.

The 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 (some waveforms/

applications require the MQME-270-T filter and/or external

transientsuppressioncircuitry).TheSection22ComplianceMatrix

Table on Page 9 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

converterconnectedtogetherthroughagroundplane.Bothcases

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-P filters in

parallel. Connecting filters in this manner may result in slightly

unequalcurrentstoflowinthepositiveandreturnpathsofeach

filter. These unequal currents may cause the internal common-

mode chokes to saturate and thus cause degraded common-mode

rejection performance.