–14–

ADDC02812DA/ADDC02815DA

REV. A

It should be noted that there are several areas of ambiguity with

respect to CE102 measurements that may concern the systems

engineer. One area of ambiguity in this measurement is the

nature of the load. If it is constant, then the ripple voltage on

the converter’s input leads is due only to the operation of the

converter. If, on the other hand, the load is changing over time,

this variation causes an additional input current and voltage

ripple to be drawn at the same frequency. If the frequency is

high enough, the converter’s filter will help attenuate this sec-

ond source of ripple, but if it is below approximately 100 kHz, it

will not. The system may then not meet the CE102 require-

ment, even though the converter is not the source of the EMI.

If this is the case, additional capacitance may be needed across

the load or across the input to the converter.

Another ambiguity in the CE102 measurement concerns

common-mode voltage. If the load is left unconnected from the

ground plane (even though the case is grounded), the common-

mode ripple voltages will be smaller than if the load is grounded.

The test specifications do not state which procedure should be

used. However, in neither case (load grounded or floating) will

the typical EMI test setup described below be exactly represen-

tative of the final system configuration EMI test. For the follow-

ing reasons, the same is true if separately packaged EMI filters

are used.

In almost all systems the output ground of the converter is ulti-

mately connected to the input ground of the system. The para-

sitic capacitances and inductances in this connection will affect

the common-mode voltage and the CE102 measurement. In

addition, the inductive impedance of this ground connection

can cause resonances, thereby affecting the performance of the

common-mode filter in the power supply.

In response to these ambiguities, the Analog Devices converter

has been tested for CE102 under a constant load and with the

output ground floating. While these measurements are a good

indication of how the converter will operate in the final system

configuration, the user should confirm CE102 testing in the

final system configuration.

CE101: This test measures emissions on the input leads in the

frequency range between 30 Hz and 10 kHz. The intent of this

requirement is to ensure that the dc/dc converter does not corrupt

the power quality (allowable voltage distortion) on the power

buses present on the platform. There are several CE101 limit

curves in MIL-STD-461D. The most stringent one applicable for

the converter is the one for submarine applications. Figure 13

shows that the converter easily meets this requirement (the return

line measurement is similar). The components at 60 Hz and its

harmonics are a result of ripple in the output of the power

source used to supply the converter.

NAVMAT Junction Temperatures: The two types of power

deratings (current and temperature) can be independent of one

another. For instance, a switching diode can meet its derating of

70% of its maximum current, but its junction temperature can

be higher than 110

°C if the case temperature of the converter,

which is not controlled by the manufacturer, is allowed to go

higher. Since some users may choose to operate the power sup-

ply at a case temperature higher than 90

°C, it then becomes

important to know the temperature rise of the hottest semicon-

ductors. This is covered in the specification table in the section

entitled “Thermal Characteristics.”

EMI CONSIDERATIONS

The ADDC02812DA and ADDC02815DA have an integral

differential- and common-mode EMI filter that is designed to

meet all applicable requirements in MIL-STD-461D when the

power converter is installed in a typical system setup (described

below). The converter also contains transient protection cir-

cuitry that permits the unit to survive short, high voltage tran-

sients across its input power leads. The purpose of this section is

to describe the various MIL-STD-461D tests and the converter’s

corresponding performance. Consult factory for additional

information.

The figures and tests referenced herein were obtained from

measurements on the ADDC02805SA, a single 5 V dc output

converter. Since the construction and topology of the dual out-

put converters are almost identical to the single output con-

verter, and the component values of the EMI differential and

common filter in the dual output converters are identical to the

single output converter, the text references these figures and

tests as typical of the ADDC02812DA and ADDC02815DA

converters.

Electromagnetic interference (EMI) is governed by MIL-STD-

461D, which establishes design requirements, and MIL-STD-

462D, which defines test methods. EMI requirements are

categorized as follows (xxx designates a three digit number):

• CExxx: conducted emissions (EMI produced internal to the

power supply which is conducted externally through its input

power leads)

• CSxxx: conducted susceptibility (EMI produced external

to the power supply which is conducted internally through

the input power leads and may interfere with the supply’s

operation)

• RExxx: radiated emissions (EMI produced internal to the

power supply which is radiated into the surrounding space)

• RSxxx: radiated susceptibility (EMI produced external to the

power supply which radiates into or through the power supply

and may interfere with its proper operation)