Si8410/20/21
4.4. RF Immunity and Common Mode Transient Immunity
The Si841x and Si842x families have very high common mode transient immunity while transmitting data. This is
typically measured by applying a square pulse with very fast rise/fall times between the isolated grounds.
Measurements show no failures up to 30 kV/µs. During a high surge event, the output may glitch low for up to
20–30 ns, but the output corrects immediately after the surge event.
The Si841x and Si842x families pass the industrial requirements of CISPR24 for RF immunity of 3 V/m using an
unshielded evaluation board. As shown in Figure 14, the isolated ground planes form a parasitic dipole antenna,
while Figure 15 shows the RMS common mode voltage versus frequency above which the Si841x becomes
susceptible to data corruption. To avoid compromising data, care must be taken to keep RF common-mode voltage
below the envelope specified in Figure 15. The PCB should be laid-out to not act as an efficient antenna for the RF
frequency of interest. RF susceptibility is also significantly reduced when the end system is housed in a metal
enclosure, or otherwise shielded.
GND1
GND2
Isolator
Dipole
Antenna
Figure 14. Dipole Antenna
5
4
3
2
1
0
500
1000
Frequency (MHz)
1500
2000
Figure 15. RMS Common Mode Voltage vs. Frequency
22
Preliminary Rev. 0.1
SILICON [ SILICON ]
