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.

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.

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.

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.

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.

FEaTuRES

• FullyqualifiedtoClassHorK

• Passivecomponentsusedformaximumtolerancein

space environments

• -55°Cto+125°Coperation

• Nominal28Vinput,0Vto50Voperation

• Upto0.8Athroughputcurrent

• 55dBattenuationtypicalat500KHz

• ComplianttoMIL-STD-461CCE-03

• CompatiblewithMIL-STD-704A-E28VDCpowerbus

anD

Input (V)

28

Current (A)

0.8

Crane Aerospace & Electronics Power Solutions

STF28-461 EMI Input Filters

Crane Aerospace & Electronics

ElectronicsGroup(InterpointBrand)

POBox97005•RedmondWA98073-9705

425.882.3100•electronics@craneae.com

www.craneae.com

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