Application information

LNBH23

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2.4

Data encoding by external tone generator (EXTM)

In order to improve design flexibility an external tone input pin is available (EXTM). The

the LNBH23 integrated tone generator (similarly to the DSQIN pin function). As a matter of

fact, the output tone waveform characteristics will be always internally controlled by the

LNBH23 tone generator and the EXTM signal will be used just as a timing control of the

for the proper control of the EXTM pin function. Before to send the TTL signal on the EXTM

or TTX bit set HIGH). As soon as the EXTM internal circuit detects the 22 kHz TTL signal

TTL signal presence on the EXTM pin, and it stops with 2 cycles ±25 µs delay after the TTL

signal is expired. Refer to the below Figure 2

2.5

I²C interface

The main functions of the IC are controlled via I²C bus by writing 8 bits on the system

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

back (SR 8 bits in read mode) to provide 8 diagnostic functions: five bits will report the

diagnostic status of five internal monitoring functions (IMON, VMON, TMON, OTF, OLF)

while, three will report the last output voltage register status (EN, VSEL, LLC) received by

the IC (see below diagnostic functions section).

2.6

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

LNBs. Additionally, the LNBH23 is provided with the LLC I²C bit that increases the selected

voltage value by +1 V to compensate the excess of voltage drop along the coaxial cable.

The LNBH23 is also compliant to the USA LNB power supply standards. In order to allow

fast transition of the output voltage from 18 V to 13 V and vice versa, the LNBH23 is

provided with the VCTRL TTL pin which keeps the output to 13 V when it is set LOW and to

controlled only through the VSEL and LLC I²C bits, that is: Even if VCTRL=0 (keeping

Figure 2.

EXTM waveform