Description

The Interpoint™ FM-704A™ EMI Filter and Transient

Suppression Module combines EMI filtering and transient

protection to handle the demanding requirements of military,

aerospace and industrial applications. As an EMI filter the

FM-704A filter reduces the reflected ripple current from DC/DC

switching converters. As a protection module, it suppresses input

transients on the power bus to protect the converter and other

downstream components.

When used in conjunction with Interpoint converters, the

FM-704A EMI filter reduces reflected input ripple current by a

minimum of 60 dB at 500 kHz and 55 dB at 1 MHz (see Electrical

Characteristics table on page 5 and Figures on page 6). This

attenuation gives the converter/filter combination performance

exceeding MIL-STD-461C’s CE03 test. Although the FM-704A

filter effectively attenuates the ripple generated by switching

converters, it will not suppress RF applied to its input terminals.

FM-704A filters are rated to operate from -55°C to +125°C

baseplate temperature. To meet MIL-STD-1275A and MIL-STD-

704A requirements, derate output power linearly from 40 watts at

105°C to 20 watts at 125°C. See Figure 9.

To provide protection for itself and converters, the FM-704A filter

blocks transients as required by the following standards:

MIL-STD-704A

Panavia SP-P-90001

MIL-STD-461A through F British Standard BS3G100

MIL-STD-1275

Civil Aircraft D0160B

Refer to the Electrical Characteristics table on page 5 for more

information.

Reverse polarity spikes of up to 100 V will not damage the filter,

however the spikes will not be blocked by the filter.

To keep internal power dissipation to safe operating levels, the

input current should never exceed 2.5 amps at 16 Vin or 1.0 amp

at 40 Vin. When the FM-704A filter is used with PWM (Pulse

Width Modulated) converters, Iline will vary as Power / Vline

and 2.5 amps maximum at 16 Vin will reduce to approximately 1

amp maximum at 40 Vin. The maximum value allowed may be

less than 1 amp as determined by line transients and the safe

operating area of Figure 9.

Figure 9 illustrates the maximum allowed internal dissipation for

the FM-704A filter. To calculate watts dissipated, subtract 40

volts from the transient (VT) to determine the maximum voltage

across the filter and multiply the result by the current (the filter’s

output power, Pout divided by 40):

W = (VT - 40) x Pout /40

For example, with 20 watts output and a transient of 400 volts:

W = (400 - 40) x 20/40 = 180

The curve of Figure 9 shows that 180 W can be dissipated for up

to 4 milliseconds.

The inhibit function allows the FM-704A filter to be used as a

high-side switch. When the inhibit terminal (pin 6) is left open or

pulled high, the FM-704A filter is enabled. When the terminal is

grounded, the filter shuts off output power.

A soft start function helps reduce inrush current and start-up

overshoot when the filter is initially powered or when it is

released from the inhibit mode.

An undervoltage lockout feature shuts off output power when

input voltage falls below a specified level. Refer to Figure 8 for

more information.

To minimize EMI, common mode noise, the case of the filter

must be connected to the case of the converter through a low

impedance connection.

MoDEL

FM-704A

40 WATT

Features

active transient suppression

undervoltage lockout

-55°C to +125°C operation

•

16 to 40 VDC input

•

Up to 60 dB attenuation at 500 kHz.

•

Inhibit function

•

Compliant to MIL-STD-461A-F

•

Crane Aerospace & Electronics Power Solutions

FM-704a eMi input Filter and transient suppression Module

Crane Aerospace & Electronics

Power Solutions - Interpoint Products

10301 Willows Road NE, Redmond, WA 98052

+1.425.882.3100•power@crane-eg.com

www.craneae.com/interpoint

Page 1 of 9

FM-704A Rev C - 2011.11.07

28 Volt input – 40 Watt