MQME-28-P
Current:
20 A
Technical Specification
BASIC OPERATION AND FEATURES
The MQME-28-P 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 res-
onances 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-28-P EMI filter includes a large bulk capacitor (also
X7R) with a series damping resistor to correct for the unstabiliz-
ing 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.
The input voltage surge and spike compliance matrix shown on
Page 8 displays the worst case requirements listed in various 28V
Military (Vehicle and Aircraft) and Civil Aircraft standards. The
MQME-28-P EMI filter is designed to handle all of the short dura-
tion voltage spike requirements of these standards (with certain
assumptions regarding DEF-STAN 61-5). Some of the long dura-
tion voltage surge requirements remain within the 50V maximum
transient rating of a SynQor MQFL-28 DC/DC converter. The oth-
ers require the transient suppression circuitry of an MQME-28-T
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 tran-
sient suppression circuitry.
When used with SynQor’s DC/DC converters, the MQME-28-P
EMI filter is designed to pass all of the relevant MIL-STD-
461C/D/E requirements to their most stringent limits. The MIL-
STD-461 Compliance Matrix Table on Page 7 lists these require-
ments 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 appli-
cations specified in RTCA/DO-160E Section 22 (Lightning
Induced Transient Susceptibility) to Level 4 (some
waveforms/applications require the MQME-28-T filter and/or
external transient suppression circuitry). The Section 22
Compliance Matrix 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
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-28-P filters in par-
allel. 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.
Product # MQME-28-P
Phone 1-888-567-9596
Doc.# 005-2ME028P Rev. A
5/1/08
Page 6
SYNQOR [ SYNQOR WORLDWIDE HEADQUARTERS ]
