Application information LNBTVS
6/13 DocID17882 Rev 4
Figure 8. Application schematic with LNBH25/26 and LNBTVSx
LNBHxx output is usually connected to the antenna cable of digital satellite receivers.
Atmospheric phenomenon can cause high voltage discharges on the antenna cable causing
damages to the attached devices.
In applications where it is required to be protected against lightning surges, transient voltage
suppressor (TVS) devices like LNBTVSx-22xx can be used to protect LNBHxx and the other
devices electrically connected to the antenna cable.
The LNBTVSx-22xx diodes are dedicated lightning and electrical overstress surge
protection for LNBHxx voltage regulators. These protection diodes were designed to comply
with the stringent IEC 61000-4-5 standard with surges up to 500 A with a whole range of
products.
TVS diodes have intrinsic capacitance that attenuates the RF signal. For this reason, the
LNBTVSx-22xx cannot be directly connected to the IF (RX/TX) cable connector that carries
the RF signals coming from the LNB. To suppress the effect of the intrinsic capacitance, an
inductance must be placed in series with the TVS diode (see Figure 9). The goal of the L
series and LNBTVC inductance is to be transparent at 22 kHz and to reject frequencies
higher than 900 MHz.
The value of the series inductance is usually > 13 nH, with a current capability higher than
the I
pp
(peak pulse current) expected during the surge.
L1
C3
Vin
12V
to LNB IF connector
LX
Vup
Vout
ADDR
C4
LNBH25
(or LNBH26 sec - A/B)
{
I
2
C Bus
SDA
SCL
P-GND A-GND
D1
C5
ISEL
R1 (RSEL)
Byp
C7
DSQIN
C2
C1
Vcc
D2
FLT
DiSEqC
Envelope TTL
or
DiSEqC
22KHz TTL
D3
Lseries > 13 nH
D4
LNBTVSxx
