TA0321 Datasheet, PDF (6/12 Pages) STMicroelectronics – TECHNICAL ARTICLE

4 The Need for Lightning Protection
4 The Need for Lightning Protection
TA0321
The LNB is remotely powered from the satellite receiver. The same coaxial cable that carries
the IF signal from the LNB to the receiver carries power from the receiver to the LNB. The 13V
to 18V DC is generated by a dedicated IC, a LNB Voltage Regulator.
This device can be damaged by any lightning strike on the coaxial cable or the antenna that can
generate high current - high voltage surge at the voltage regulator.
This surge can be simulated according to the IEC61000-4-5 standard:
● t_r/t_f = 8/20 µs
● V_pp = 3 kV to 6 kV
● R = 12 Ω
● I_pp = 250 A to 500 A
Figure 5. IEC61000-4-5 current waveform
I
I
I/2
t
8 µs 20 µs
In case of lightning events, the current surge at the LNB voltage regulator (IC) inputs ranges
from 250 A (when 3 kV is applied) to 500 A (when 6 kV is applied). This IC can not withstand
such high value energy.
To comply with this IEC regulation and to protect the LNB Voltage Regulator IC against any
damage from lightning events, a dedicated and optimized protection device is required in front
of the voltage regulator.
6/12