LNBH26L

Application information (valid for each section A/B)

Doc ID 022876 Rev 1

5/28

2

Application information (valid for each section A/B)

This IC has a built-in DC-DC step-up converter that, from a single source (8 V to 16 V),

/ 18 V LNB output voltages plus the 22 kHz DiSEqC tone) to work with a minimum

dissipated power of 0.5 W typ. @ 500 mA load (the LDO drop voltage is internally kept at

typically). The step-up converter soft-start function reduces the inrush current during

startup. The SS time is internally fixed at 4 ms typ. to switch from 0 to 13 V and 6 ms typ. to

switch from 0 to 18 V.

2.1

DISEQC data encoding (DSQIN pin)

The internal 22 kHz tone generator is factory trimmed in accordance with the DiSEqC

standards, and can be activated in 3 different ways:

1) by an external 22 kHz source DiSEqC data connected to the DSQIN logic pin (TTL

compatible). In this case the I²C tone control bits must be set: EXTM=TEN=1.

2) by an external DiSEqC data envelope source connected to the DSQIN logic pin. In this

case the I²C tone control bits must be set: EXTM=0 and TEN=1.

3) through the TEN I²C bit if the 22 kHz presence is requested in continuous mode. In this

case the DSQIN TTL pin must be pulled high and the EXTM bit set to “0”.

2.2

Data encoding by external 22 kHz tone TTL signal

In order to improve design flexibility, an external tone signal can be input to the DSQIN pin

by setting the EXTM bit to “1”.

LNBH26L integrated tone generator.

The output tone waveforms are internally controlled by the LNBH26L tone generator in

terms of rise/fall time and tone amplitude, while, the external 22 kHz signal on the DSQIN

pin is used to define the frequency and the duty cycle of the output tone. A TTL compatible

22 kHz signal is required for the proper control of the DSQIN pin function. Before sending

the TTL signal on the DSQIN pin, the EXTM and TEN bits must be previously set to “1”. As

soon as the DSQIN internal circuit detects the 22 kHz TTL external signal code, the

signal activation, and it stops with about 60 µs delay after the 22 kHz TTL signal on DSQIN

has expired. Refer to

Figure 2.

Figure 2.

Tone enable and disable timing (using external waveform)

AM10426v1

~ 1 µs

~ 60 µs

DSQIN

Tone

Output