LNBH23L

Application information

Doc ID 15335 Rev 4

5/25

2

Application information

This IC has a built-in DC-DC step-up converter that, from a single source from 8 V to 15 V,

dissipated power of 0.55 W typ. @ 500 mA load (the linear post-regulator drop voltage is

Note:

2.1

DiSEqC™ data encoding

The 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. Besides the internal 22 kHz tone

generator, the auxiliary modulation pin (EXTM) can be driven by an external 22 kHz source

and in this case TTX must be set to low.

2.2

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

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

can be removed (see Figure 5) saving the external components cost. If this configuration is

used keep TTX set to low.

2.3

connection

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

internal circuit must be preventively set ON by setting the TTX function to High. This can be

Figure 3). After TTX is set to High the internal 22 kHz tone generator available through the

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. As soon as the tone transmission is expired, the