LNBH23PPR datasheet(5/32 Pages) STMICROELECTRONICS

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LNBH23

Application information

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Application information

This IC has a built-in DC-DC step-up converter with integrated NMOS that, from a single

source from 8 V to 15 V, generates the voltages (VUP) that let the linear post-regulator to

work at a minimum dissipated power of 0.375 W Typ. @ 500 mA load (the linear post-

regulator drop voltage is internally kept at VUP-VORX=0.75 V typ.). An under voltage lockout

circuit will disable the whole circuit when the supplied VCC drops below a fixed threshold (6.7

V typically).

Note:

In this document the output voltage (VO) is intended as the voltage present at the linear

post-regulator output (VORX pin).

2.1

DiSEqCTM data encoding and decoding

The new internal 22 kHz tone generator (patent pending) is factory trimmed in accordance

to the standards, and can be selected by I²C interface TTX bit (or TTX pin) and activated by

a dedicated pin (DSQIN) that allows immediate DiSEqCTM data encoding, or through TEN

I²C bit in case the 22 kHz presence is requested in continuous mode. In stand-by condition

(EN bit LOW) The TTX function must be disabled setting TTX to LOW.

2.2

DiSEqCTM 2.0 implementation

The built-in 22 kHz tone detector completes the fully bi-directional DiSEqCTM 2.0 interfacing

(see Note: 1). It’s input pin (DETIN) must be AC coupled to the DiSEqCTM BUS, and

extracted PWK data are available on the DSQOUT pin. To comply to the bi-directional

DiSEqCTM 2.0 bus hardware requirements an output R-L filter is needed. The LNBH23 is

provided with two output pins, one for the dc voltage output (VoRX) and one for the 22 kHz

tone transmission (VoTX). The VoTX must be activated only during the tone transmission

while the VoRX provides the 13/18 V output voltage. This allows the 22 kHz Tone to pass

without any losses due to the R-L filter impedance (see Figure 4 typ. application circuit).

During the 22 kHz transmission, in DiSEqCTM 2.0 applications, activated by DSQIN pin or

by the TEN bit, the VoTX pin must be preventively set ON by the TTX function. This can be

controlled both through the TTX pin and by I²C bit. As soon as the tone transmission is

expired, the VoTX must be disabled by setting the TTX to LOW to set the device in the 22

kHz receiving mode. The 13/18 V power supply is always provided to the LNB from the VoRX

pin through the R-L filter.

2.3

DiSEqCTM 1.X implementation

When the LNBH23 is used in DiSEqCTM 1.x applications the R-L filter is always needed for

the proper operation of the new 22 kHz tone generator (patent pending. See application

circuit). Also in this case, the TTX function must be preventively enabled before to start the

22 kHz data transmission and disabled as soon as the data transmission has been expired.

The tone can be activated both with the DSQIN pin or the TEN I²C bit. The DSQIN internal

circuit activates the 22 kHz tone on the VoTX output with 0.5 cycles ±25 µs delay from the

TTL signal presence on the DSQIN pin, and it stops with 1 cycles ±25 µs delay after the TTL

signal is expired.

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