ADM488/ADM489

–10–

REV. 0

The ADM488/ADM489 comfortably meets Classification 1 at

the most stringent (Level 3) requirement. In fact, field strengths

up to 30 V/m showed no performance degradation and error-

free data transmission continued even during irradiation.

Table IV.

Level

V/m

Field Strength

11

23

310

EMI EMISSIONS

The ADM488/ADM489 contains internal slew rate limiting in

order to minimize the level of electromagnetic interference

generated. Figure 22 shows an FFT plot when transmitting a

150 kHz data stream.

10

0%

100

90

10dB/DIV

500kHz/DIV

0

5MHz

Figure 22. Driver Output Waveform and FFT Plot Trans-

mitting @ 150 kHz

As may be seen, the slew limiting attenuates the high frequency

components. EMI is therefore reduced, as are reflections due to

improperly terminated cables.

EN55022, CISPR22 defines the permitted limits of radiated

and conducted interference from Information Technology

Equipment (ITE).

The objective is to control the level of emissions, both con-

ducted and radiated.

For ease of measurement and analysis, conducted emissions are

assumed to predominate below 30 MHz, while radiated emis-

sions predominate above this frequency.

CONDUCTED EMISSIONS

This is a measure of noise that is conducted onto the mains

power supply. The noise is measured using a LISN (Linc Im-

pedance Stabilizing Network) and a spectrum analyzer. The test

setup is illustrated in Figure 23. The spectrum analyzer is set to

scan the spectrum from 0 MHz to 30 MHz. Figure 24 shows

that the level of conducted emissions from the ADM488/

ADM489 are well below the allowable limits.

SPECTRUM

ANALYZER

DUT

LISN

PSU

Figure 23. Conducted Emissions Test Setup

LOG FREQUENCY (0.15–30) – MHz

0.3

0.6

13

6

10

30

80

0

70

40

30

20

10

60

50

LIMIT

Figure 24. Conducted Emissions