MQME-28-P
Current:
20 A
Technical Specification
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.
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 50Ω to chassis ground on each input line.
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.
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
waveforms/applications require the MQME-28-T filter and/or
external transient suppression circuitry). The Section 22
4
(some
Compliance Matrix Table on Page 9 lists these waveforms and
applications and describes the setup used to pass them.
Product # MQME-28-P
Phone 1-888-567-9596
www.synqor.com
Doc.# 005-2ME028P Rev. A
5/1/08
Page 6
SYNQOR [ SYNQOR WORLDWIDE HEADQUARTERS ]
