Component selection guidelines

AN3352

16/26

Doc ID 018526 Rev 3

damage to the attached devices. In applications where it is required to protect against

lightning surges, transient voltage suppressor (TVS) devices like the LNBTVSx-22xx can be

used to protect the LNBH24L and the other devices electrically connected to the antenna

cable.The LNBTVSx-22xx diodes, developed by STMicroelectronics, are dedicated to

lightning and electrical overstress surge protection for LNBHxx voltage regulators. These

protection diodes were designed to comply with the stringent IEC61000-4-5 standard with

surges up to 500 A in a whole range of products.

Note:

TVS diodes have intrinsic capacitance that attenuates the RF signal. For this reason, the

the RF signals coming from the LNB. To suppress effects of the intrinsic capacitance, an

inductance must be placed in series with the TVS diode (see Figure 6 example). The goal of

the L series inductance added to the CLNBTVS 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

The selection of the TVS diode must be based on the maximum peak power dissipation that

the diode is capable of supporting.

Select the TVS diode which is capable of supporting the required Ipp (A) value indicated in

Table 7

.

Figure 8.

Example of LNBTVS diode connection

D2

VoRX

EXTM

LNBH24L

C10

VoTX

C15

R9

D3

1N4007

D6

LNBTVSx -22xx

IF Connector

Lseries >13nH

D2

C10

R9

Table 7.

Recommended LNBTVS

Vendor

Part number

Ipp (A) 8/20 µs

STMicroelectronics

LNBTVS4-220S

23.1

334

LNBTVS4-221S

23.1

334

LNBTVS4-222S

23.1

334

LNBTVS6-221S

23.1

500