ASM202E/ASM±±8±A
CONDUCTED EMISSIONS
IEC1000-4-3 RADIATED IMMUNITY
Conducted emissions is a measure of noise conducted onto the
mains power supply. Switching transients from the charge pump
that are 20 V in magnitude and that contain significant energy
can lead to conducted emissions. Another source of conducted
emissions is the overlap in switch-on times in the charge-pump
voltage converter. In the voltage doubler shown in Figure 23, if
S2 is not fully turned off before S4 turns on, a transient current
glitch occurs between VCC and GND that results in conducted
emissions. Therefore, it is important that the switches in the
charge pump guarantee break-before-make switching under all
conditions to prevent instantaneous short-circuit conditions.
IEC1000-4-3 (previously IEC801-3) describes the measure-
ment method and defines the levels of immunity to radiated
electromagnetic fields. It was originally intended to simulate the
electromagnetic fields generated by portable radio transceivers
and other devices that generate continuous wave-radiated
electromagnetic energy. Its scope has since been broadened to
include spurious EM energy, which can be radiated from
fluorescent lights, thyristor drives, inductive loads, and
other sources.
Testing for immunity involves irradiating the device with an
EM field. There are various methods of achieving this, including
use of anechoic chamber, stripline cell, TEM cell, and GTEM
cell. A stripline cell consists of two parallel plates with an electric
field developed between them. The device being tested is placed
within the cell and exposed to the electric field. There are three
severity levels that have field strengths ranging from 1 V to
10 V/m. Results are classified in a similar fashion to those for
IEC1000-4-2.
The ADM202E is designed to minimize the switching transients
and ensure break-before-make switching, thereby minimizing
conducted emissions. This results in emission levels well below
the specified limits. No additional filtering or decoupling, other
than the recommended 0.1 µF capacitor, is required.
Conducted emissions are measured by monitoring the mains
line. The equipment used consists of a spectrum analyzer and a
LISN (line impedance stabilizing network) that essentially
presents a fixed impedance at RF. The spectrum analyzer scans
for emissions of up to 30 MHz; a plot for the ADM202E is
shown in Figure 25.
•
•
Classification 1: Normal operation
Classification 2: Temporary degradation or loss of
function that is self-recoverable when the interfering
signal is removed
•
•
Classification 3: Temporary degradation or loss of function
that requires operator intervention or system reset when
the interfering signal is removed
S3
S4
S1
S2
V
V+ = 2V
CC
CC
C1
C3
GND
V
CC
Classification 4: Degradation or loss of function that is not
recoverable due to damage
INTERNAL
OSCILLATOR
The ADM202E/ADM1181A products easily meet Classification 1
at the most stringent (Level 3) requirement. In fact, field strengths
of up to 30 V/m showed no performance degradation, and error-
free data transmission continued even during irradiation.
Figure 23. Charge-Pump Voltage Doubler
∅1
∅2
Table 6. Test Severity Levels (IEC1000-4-3)
Level
Field Strength ꢀ/m
1
2
3
1
3
10
SWITCHING GLITCHES
EMISSIONS/INTERFERENCE
Figure 24. Switching Glitches
EN55 022 and CISPR22 define the permitted limits of radiated
and conducted interference from information technology (IT)
equipment. The objective of the standard is to minimize the
level of emissions, both conducted and radiated. For ease of
measurement and analysis, conducted emissions are assumed to
predominate below 30 MHz, and radiated emissions are
assumed to predominate above 30 MHz.
Rev. C | Page 12 of 16
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