Component selection guidelines

AN3115

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Doc ID 16830 Rev 3

can be calculated using Equation 1.

Equation 3

2.4

TVS diode (D6)

The LNBH23L device is directly connected to the antenna cable in a set-top box.

Atmospheric phenomenon can cause high voltage discharges on the antenna cable causing

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

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

used to protect the LNBH23L 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 a current capability higher than

Vin

Vout

Iout

Id

×

=

Table 7.

Recommended Schottky diode

Vendor

Part number

STMicroelectronics

1N5818

1 A

0.50 V

1N5819

1 A

0.55 V

STPS130A

1 A

0.46 V

STPS1L30A

1 A

0.30 V

STPS2L30A

2 A

0.45 V

1N5822

3 A

0.52 V

STPS340

3 A

0.63 V

STPS3L40A

3 A

0.5 V