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ADDC02803SCTV

28 V/66 W/100 W DC/DC Converters with Integral EMI Filter

Analog Devices 

ADDC02803SC/ADDC02805SA

CE102: This test measures emissions in the frequency range

between 10 kHz and 10 MHz. The measurements are made on

both of the input leads of the converter, which are connected to

the power source through LISNs. The intent of this requirement,

in the lower frequency portion of the 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. At higher frequencies, the intent is to serve as a sepa-

rate control from RE102 on potential radiation from power

leads that may couple into sensitive electronic equipment.

Figure 20 shows the CE102 limit and the measurement taken

from the +VIN line. While the measurement taken from the

input return line is slightly different, both comfortably meet the

MIL-STD-461D, CE102 limit. (Reference the last section of

EMI Considerations for how to adjust the external components

in the test setup circuit to increase the margin between the

specification limit and the measured results.)

CS101: This test measures the ability of the converter to reject

low frequency differential signals, 30 Hz to 50 kHz, injected on

the dc inputs. The measurement is taken on the output power

leads. The intent is to ensure that equipment performance is

not degraded from ripple voltages associated with allowable

distortion of power source voltage waveforms. Figures 11 and

12 show typical audio susceptibility graphs. Note that according

to the MIL-STD-461D test requirements, the injected signal

between 30 Hz and 5 kHz has an amplitude of 2 V rms and

from 5 kHz to 50 kHz the amplitude decreases inversely with

frequency to 0.2 V rms. The curve of the injected signal should

be multiplied by the audio susceptibility curve to determine the

output ripple at any frequency. When this is done, the worst

case output ripple at the frequency of the input ripple occurs at

5 kHz, at which point there is typically a 25 mV peak-to-peak

output ripple.

It should be noted that MIL-STD-704 has a more relaxed

requirement for rejection of low frequency differential signals

injected on the dc inputs than MIL-STD-461D. MIL-STD-704

calls for a lower amplitude ripple to be injected on the input in a

narrower frequency band, 10 Hz to 20 kHz.

CS114: This test measures the ability of the converter to oper-

ate correctly during and after being subjected to currents in-

jected into bulk cables in the 10 kHz to 400 MHz range. Its

purpose is to simulate currents that would be developed in these

cables due to electromagnetic fields generated by antenna trans-

missions. The converter is designed to meet the requirements

of this test when the current is injected on the input power leads

cable. Consult factory for more information.

CS115: This test measures the ability of the converter to oper-

ate correctly during and after being subjected to 30 ns long

pulses of current injected into bulk cables. Its purpose is to

simulate transients caused by lightning or electromagnetic

pulses. The converter is designed to meet this requirement

when applied to its input power leads cable. Consult factory for

more information.

CS116: This test measures the ability of the converter to oper-

ate correctly during and after being subjected to damped sinu-

soid transients in the 10 kHz to 100 MHz range. Its purpose is

to simulate current and voltage waveforms that would occur

when natural resonances in the system are excited. The con-

verter is designed to meet this requirement when applied to its

input power leads cable. Consult factory for more information.

RE101: This requirement limits the strength of the magnetic

field created by the converter in order to avoid interference with

sensitive equipment located nearby. The measurement is made

from 30 Hz to 100 kHz. The most stringent requirement is for

the Navy. Figure 21 shows the test results when the pickup coil

is held 7 cm above the converter. As can be seen, the converter

easily meets this requirement.

RE102: This requirements limits the strength of the electric

field emissions from the power converter to protect sensitive

receivers from interference. The measurement is made from

10 kHz to 18 GHz with the antenna oriented in the vertical

plane. For the 30 MHz and above range, the standard calls for

the measurement to be made with the antenna oriented in the

horizontal plane as well.

In a typical power converter system setup, the radiated emis-

sions can come from two sources: 1) the input power leads as

they extend over the two meter distance between the LISNs and

the converter, as required for this test, and 2) the converter

output leads and load. The latter is likely to create significant

emissions if left uncovered, since minimal EMI filtering is

provided at the converter’s output. It is typical, however,

that the power supply and its load would be contained in a

conductive enclosure in applications where this test is applicable.

For this test a metal screen was therefore used to cover the

converter and its load.

Figure 22 shows test results for the vertical measurement and

compares them against the most stringent RE102 requirement;

the horizontal measurement (30 MHz and above) was similar.

As can be seen, the emissions just meet the standard in the

18 MHz–28 MHz range. This component of the emissions is

due to common-mode currents flowing through the input power

leads. As mentioned in the section on CE102 above, the level

of common-mode current that flows is dependent on how the

load is connected. This measurement is therefore a good indi-

cation of how well the converter will perform in the final con-

figuration; the user should confirm RE102 testing in the final

system. (Reference the last section of EMI Considerations for

how to adjust the external components in the test setup circuit

to increase the margin between the specification limit and the

measured results.)

RS101: This requirement is specialized and intended to check

for sensitivity to low frequency magnetic fields in the 30 Hz to

50 kHz range. The converter is designed to meet this require-

ment. Consult factory for more information.

RS103: This test calls for correct operation during and after the

unit under test is subjected to radiated electric fields in the 10 kHz

to 40 GHz range. The intent is to simulate electromagnetic

fields generated by antenna transmissions. The converter is

designed to meet this requirement. Consult factory for more

information.

–14–

REV. A

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