Introduction

LNBH24L

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Doc ID 16857 Rev 2

22 kHz tone (see Figure 3: LNBH24L with internal tone for DiSEqC 1.X applications). The

22 kHz transmission by DSQIN pin or by the TEN bit.The DSQIN internal circuit activates

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

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

2.5

PDC optional circuit for DISEQC™ 1.X applications using

In some applications, at light output current (< 50 mA) and in case of heavy output

capacitive load, the 22 kHz tone can be distorted. In this case it is possible to add the

"Optional" external components shown in the typical application circuit (see Figure 4:

DiSEqC 1.x using external 22 kHz tone generator source through EXTM pin

) connected

output capacitance only when the internal 22 kHz tone is activated.

2.6

I²C interface

The main functions of the IC are controlled via I²C bus by writing 6 bits on the system

register (SR 8 bits in write mode). On the same register there are 5 bits that can be read

back (SR 8 bits in read mode) to provide the diagnostic flags of two internal monitoring

functions (OTF, OLF) and three output voltage register status (EN, VSEL, LLC) received by

the IC (see Section 2.8: Diagnostic and protection functions). In read mode there are 3 test

bits (TEST1-2-3) that must be disregarded from the MCU. While, in write mode, there 2 Test

bits (TEST4-5) that must be always set LOW. Each section (A/B) has two selectable I²C

addresses selectable respectively, by the ADDR-A and ADDR-B pins (see Table 11:

Address pins characteristics

).

2.7

Output voltage selection

When the IC sections are in stand-by mode (EN bit LOW), the power blocks are disabled.

When the regulator blocks are active (EN bit HIGH), the output can be logic controlled to be

13 or 18 V by mean of the VSEL bit (voltage SELect) for remote controlling of non-DiSEqC

LNBs. Additionally, the LNBH24L is provided with the LLC I²C bit that increase the selected

voltage value to compensate possible voltage drop along the output line. In stand-by

condition (EN bit LOW) all the I²C bits and the TTX pin must be set LOW (if the TTX pin is

not used it can be left floating but the TTX bit must be set LOW during the stand-by

condition).

2.8

Diagnostic and protection functions

The LNBH24L has two diagnostic internal functions provided via I²C bus by reading 2 bits on

the system register (SR bits in read mode). The diagnostic bits are, in normal operation (no