LNBH24L datasheet(5/25 Pages) STMICROELECTRONICS

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LNBH24L

Introduction

Doc ID 16857 Rev 2

5/25

Introduction

The LNBH24L includes two completely independent sections. Unless for the VCC and I²C

inputs, each circuit can be separately controlled and have its independent external

components. All the below specification must be considered equal for both sections (A/B).

2.1

Application information (valid for each section A/B)

This IC has a built-in DC-DC step-up converter 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 0.55 W typ. @ 500 mA load per channel (the linear post-regulator drop

voltage is internally kept at VUP - VOUT = 1.1 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 VOUT is intended as the voltage present at the linear post-regulator

output (VoRX pin).

2.2

DiSEqC™ data encoding

The new internal 22 kHz tone generator 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 DiSEqC™ 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.

2.3

DiSEqC™ 1.X implementation by EXTM pin

In order to improve design flexibility and reduce the total application cost, an analogic

modulation input pin is available (EXTM) to generate the 22 kHz tone superimposed to the

VoRX DC output voltage. An appropriate DC blocking capacitor must be used to couple the

modulating signal source to the EXTM pin. If the EXTM solution is used the output R-L filter

can be removed (see Section 5: Application circuits) saving the external components

cost.The pin EXTM modulates the VoRX voltage through the series decoupling capacitor, so

that:

Where VoRX(AC) and VEXTM(AC) are, respectively, the peak to peak voltage on the VoRX

and EXTM pins while GEXTM is the voltage gain from EXTM to VoRX.

2.4

DISEQC™ 1.X implementation with VoTX and EXTM pin

connection

If an external 22 kHz tone source is not available, it is possible to use the internal 22 kHz

tone generator signal available through the VoTX pin to drive the EXTM pin. By this way the

EXTM

)

(

EXTM

)

(

oRX

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