ADDC02808PB

REV. A

–16–

In almost all systems the output ground of the converter is

ultimately connected to the input ground of the system. The

parasitic capacitances and inductances in this connection will

affect the common-mode voltage and the CE102 measure-

ment. In addition, the inductive impedance of this ground

connection can cause resonances, thereby affecting the perfor-

mance of the common-mode filter in the power supply.

In response to these ambiguities, the Analog Devices’ con-

verter 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 busses present on the platform. There are several

CE101 limit curves in MIL-STD-461D. The most stringent

one app-licable for the converter is the one for submarine

applications. Figure 11 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.

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 con-

nected 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

busses present on the platform. At higher frequencies, the

intent is to serve as a separate control from RE102 on potential

radiation from power leads which may couple into sensitive

electronic equipment.

Figure 12 shows the CE102 limit and the measurement taken

input return line is slightly different, both comfortably meet

the MIL-STD-461D, CE102 limit.

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.

Figure 7 shows a typical audio susceptibility graph. Note that

according to the MIL-STD-461D test requirements, the in-

jected 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 in-

jected 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 typi-

cally 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 13 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.

A metal screen enclosure was therefore used to cover the con-

verter and its load for this test.

Figure 14 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, but the user should confirm RE102 testing in the

final system.