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dc1794afa
DEMO MANUAL DC1794A
operAting principles
EMI mitigation techniques used include the following:
1. Board/ground plane size has been minimized. This
reduces the dipole antenna formed between the logic
side and isolated side ground planes.
2. Top signal routing and ground floods have been opti-
mized to reduce signal loops, minimizing differential
mode radiation.
3. A high ESR tantalum capacitor is included to minimize
board resonances and prevent voltage spikes due to
hot plugging of the input supply voltage.
4. Optional discrete bridge capacitors (C3, C4) can be
mounted between GND2 and GND. The discrete ca-
pacitors provide additional attenuation at frequencies
below 300MHz as shown in Figure 1. Capacitors are
safety rated type Y1, manufactured by Vishay, part #
VY115K31Y5SQ63V0.
EMI performance is shown in Figure 1, measured using
a Gigahertz Transverse Electromagnetic (GTEM) cell and
method detailed in IEC 61000-4-20, “Testing and Mea-
surement Techniques—Emission and Immunity Testing
in Transverse Electromagnetic Waveguides”.
CISPR 22 CLASS B LIMIT
DETECTOR = QuasiPeak
RBW = 120kHz
VBW = 300kHz
SWEEP TIME = 17s
# OF POINTS = 501
FREQUENCY (MHz)
0 100 200 300 400 500 600 700 800 900 1000
–30
–20
–10
0
10
20
30
40
50
60
AMPLITUDE (dBµ
V/m)
DC1794A F01
Figure 1. DC1794A Radiated Emissions
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