Crane Aerospace & Electronics Power Solutions
STF28-461 EMI Input Filters
28 VOlT INPuT – 0.8 aMP
FEaTuRES
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Fully qualified to Class H or K
Passive components used for maximum tolerance in
space environments
-55°C to +125°C operation
Nominal 28 V input, 0 V to 50 V operation
Up to 0.8 A throughput current
55 dB attenuation typical at 500KHz
Compliant to MIL-STD-461C CE-03
Compatible with MIL-STD-704 A-E 28 VDC power bus
i
nput
V
Oltage
anD
C
urrent
Input (V)
28
Current (A)
0.8
DESCRIPTION
The STF28-461™ EMI filter module has been designed as
a companion for Interpoint SMSA flyback power converters.
Multiple SMSA power converters can be operated from a single
filter provided the total power line current does not exceed the
filter maximum rating. The STF filter will reduce the SMSA’s
power line reflected ripple current to within the limit of MIL-STD-
461C, Method CE03. The STF filter is fabricated using thick film
hybrid technology and is sealed in a metal package for space,
military, aerospace and other applications requiring EMI suppres-
sion.
For SMHF and SLH converters a 4 µF (or greater) ceramic cap
is needed between the filter and converter to complete the last
inductive stage of this STF filter. This will ensure unconditional
stability when used with the SMHF or SLH. The SMSA does not
require this.
O
ptiOnal
D
amping
C
irCuit
O
peratiOn
The SMSA power converter has an internal 2 µF ceramic
capacitor across its input power terminals. When the SMSA
and STF filters are used together, this capacitor becomes part
of the filter and forms its final LC output section. The STF filter
provides both differential and common mode rejection bringing
DC/DC converters into compliance with MIL-STD-461C CE03. It
is designed to be used with the SMSA, SMHF, and SLH Series
of converters. The STF filter can be used with multiple converters
up to the rated current of the filter. For more information, contact
your Interpoint representative.
The optional damping circuit (Figure 2) can be used to prevent
filter overshoot caused by MIL-STD-704A 80 V, or other, tran-
sients having rise times of less than 200 µSec. This damping can
be alternately provided with a 1.50
V
resistor in series with the
filter positive input where the additional line loss can be tolerated.
For transients with rise times of greater than 200 µSec, there is
no overshoot and the damping circuit is not required.
S
Creening
The STF28-461 filter offers three screening options: Space
Prototype (O), Class H, or Class K. Radiation tolerant to
Radiation Hardness Assurance (RHA) levels of “-” (O) or “H”,
per MIL-STD-38534. Interpoint model numbers use an “O” in
the RHA designator position to indicate the “-” (dash) Radiation
Hardness Assurance level of MIL-PRF-38534, which is defined
as “no RHA”. See “Class H and K, MIL-PRF-38534 Screening”
tables, for descriptions.
Crane Aerospace & Electronics
Electronics Group (Interpoint Brand)
PO Box 97005 • Redmond WA 98073-9705
425.882.3100 • electronics@craneae.com
www.craneae.com
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