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9

ARM28XXT Series

Additional Filtering

Figure V. ARF461 Input EMI Filter

An external filter may also be added to the output where

circuit requirements dictate extremely low output ripple

noise. The output filter described by Figure VI has been

characterized with the ARM2815T using the values shown

in the associated material list.

It is important to be aware that when filtering high frequency

noise, parasitic circuit elements can easily dominate filter

performance. Therefore, it is incumbent onthe designer to

exercise care when preparing a circuit layout for such

devices. Wire runs and lengths should be minimized, high

frequency loops should be avoided and careful attention

paid to the construction details of magnetic circuit elements.

Tight magnetic coupling will improve overall magnetic

performance and reduce stray magnetic fields.

Figure VI. External Output Filter

Measurement techniques can impose a significant influence

on results. All noise measurements should be measured

with test leads as close to the device output pins and as

short as physically possible. Probe ground leads should

be kept to a minimum length.

Although internal filtering is provided at both the input and

output terminals of the ARM2800 series, additional filtering

may be desirable in some applications to accommodate

more stringent system requirements.

While the internal input filter of Figure IV keeps input ripple

current below 100 mA

p-p

, an external filter is available that

will further attenuate this ripple content to a level below the

CE03 limits imposed by MIL-STD-461B. Figure V is a

general diagram of the Advanced Analog ARF461 filter

module designed to operate in conjunction with the

ARM2800 series converters to provide that attenuation.

This circuit as shown in Figure V is constructed using the

same quality materials and processes as those employed

in the ARM2800 series converters and is intended for use

in the same environments. This filter is fabricated in a

complementary package style whose output pin configuration

allows pin to pin connection between the filter and the

converter. More complete information on this filter can be

obtained from the ARF461 data sheet.

+5 V

5V

Return

+15V

15V

Return

-15V

+5V Out

+5V

Return

+15V

Out

15V

Return

-15V

Out

C1

C2

C3

C4

C5

C6

C7

C8

L1

L2

L4

L3

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