Crane Aerospace & Electronics Power Solutions
FM-704a Hp eMi input Filter and transient suppression Module
28 Volt input – 160 Watt
Features
active transient suppression
undervoltage lockout
• Up to 60 dB attenuation at 500 kHz
• operating temperature -55° to +125°C
• Inhibit function
• Nominal 28 V input, 16 V to 40 V operation
• Meets MIL-STD-461A-C CEo3
MoDEL
FM-704A HP
160 WATT
Description
The Interpoint™ FM-704A HP™ 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 HP 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.
I
NTerNaL
p
ower
D
ISSIpaTIoN
MIL-STD N
oISe
M
aNageMeNT
To keep internal power dissipation to safe operating levels, the
input current should never exceed 10 amps at 16 Vin or 4 amps
at 40 Vin. When the FM-704A HP filter is used with PWM (Pulse
Width Modulated) converters,
Iline
will vary as Power / Vline
and 10 amps maximum at 16 Vin will reduce to approximately 4
amps maximum at 40 Vin. The maximum value allowed may be
less than 4 amps 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 HP 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 300 W can be dissipated for up
to 60 milliseconds.
When used in conjunction with Interpoint converters, the
FM-704A HP 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
HP filter effectively attenuates the ripple generated by switching
converters, it will not suppress RF applied to its input terminals.
T
eMperaTure
o
peraTIoN
FM-704A HP 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 160 watts
at 105°C to 80 watts at 125°C. See Figure 9.
F
eaTureS
p
roTecTIoN
To provide protection for itself and converters, the FM-704A HP
filter blocks transients as required by the following standards:
‣
MIL-STD-704A
‣
MIL-STD-461 A-F
‣
MIL-STD-1275
Refer to the Electrical Characteristics table on the 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.
The inhibit function allows the FM-704A HP filter to be used as a
high-side switch. When the inhibit terminal (pin 6) is left open or
pulled high, the FM-704A HP 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.
L
ayouT
r
equIreMeNTS
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.
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
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FM-704A HP Rev C - 2011.12.06
INTERPOINT [ INTERPOINT CORPORATION COMPANY ]
