FMSA SerieS™ eMi Filter

The Interpoint® FMSA-461 EMI filter modules have been

designed as a companion for Interpoint MSA Series™ flyback

dc -dc power converters. Multiple MSA power converters can be

operated from a single filter provided the total power line current

does not exceed the maximum current rating of the filter. The

FMSA filter will reduce the MSA’s power line reflected ripple

current to within the limit of MIL-STD-461C, Method CE03, as

shown in the example of Figure 8 on page 9.

The FMSA is fabricated using thick film hybrid technology and

is sealed in a metal package for military, aerospace and other

applications requiring EMI suppression. See case A1, Figure 15

on page 11 for dimensions. The filter uses only ceramic

capacitors for reliable high temperature operation.

The MSA power converter has an internal 2 µF capacitor across

its input power terminals. See Figure 1 on page 2. When the

MSA and FMSA filters are used together, this capacitor becomes

part of the filter and forms its final LC output section. When 2 or

3 MSAs are used with a single filter, this capacitor becomes 4 µF

or 6 µF respectively, rather than 2 µF, improving the rejection vs.

frequency.

The FMSA filter can also be used with other types of Interpoint

power converters (MHF Series™, MHF+ Series™ and MHE

Series™) to comply with CE03. For MHF, MHF+ and MHE

models, the converter has an LC type line filter such that an

inductor is seen looking into its positive input terminal. For

these converters, it is necessary to terminate the filter with a

capacitor to insure unconditionally stable operation. A capacitor

across the filter output terminals of greater than 4 µF or the

optional damping circuit shown on the connection diagram will

be adequate for stable operation. No capacitor is required for the

MSA Series models.

The optional damping circuit (Figure 2 on page 2) can be

used to prevent filter overshoot caused by MIL-STD-704A 80

volt, or other, transients having rise times of less than 200

microseconds. This damping can be alternately provided with a

1.50 Ω resistor in series with the filter’s positive input where the

additional line loss can be tolerated. For transients with rise times

of greater than 200 microseconds, there is no overshoot and the

damping circuit is not required.

The case of the filter must be connected to the case of the

converter through a low impedance connection to minimize EMI.

FeAtureS

• Attenuation

50 dB (FMSA) at 500 kHz

55 dB (FMGA) at 500 kHz

• Small footprint

• Operating temperature -55° to +125°C

• Nominal 28 volts input, 0 to 50 volts operation

• up to 0.8 amps throughput current

• Compliant to Mil-StD-461C Ce-03

• Compatible with Mil-StD-704 A-e 28 VDC power bus

MODelS

FMSA-461

0.8

FMGA-461

0.8

Crane Aerospace & Electronics Power Solutions

FMSA/FMGA eMi input Filters

Crane Aerospace & Electronics

Power Solutions – Interpoint Products

10301 Willows Rd. NE, Redmond, WA 98052

+1 425-882-3100 • power@crane-eg.com

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FMSA/FMGA Rev AA - 2015.12.15