AN3115

Block diagram and pin function description

Doc ID 16830 Rev 3

7/28

1.5

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

must be activated during the 22 kHz transmission by the DSQIN pin or by the TEN bit. The

delay from the TTL signal present on the DSQIN pin, and it stops with 1 cycle ± 25 µs delay

the TTX function. This can be controlled both through the TTX pin and the I²C bit. As soon

1.6

signal on to EXTM pin and 22 kHz tone controlled by DSQIN

pin

In some applications, at light output current (< 50 mA) having a heavy LNB output capacitive

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

external components described on Section 2.7.

1.7

22 kHz oscillator

The internal 22 kHz tone generator is factory-trimmed in accordance with current standards

and can be selected by the I²C interface TTX bit (or TTX pin) and controlled by the DSQIN

pin (TTL compatible), which allows immediate DiSEqC data encoding. If the 22 kHz tone

presence is requested in continuous mode, the internal oscillator can be activated by the I²C

Figure 3.

DiSEqC 1.X tone burst with 22 kHz IC controller

VoRx OUTPUT

Vtone signal

High-Z

STATE

High-Z

STATE

High-Z

STATE

Push -pull

Action

Push -pull

Action

VoRx OUTPUT

Vtone signal

High-Z

STATE

High-Z

STATE

High-Z

STATE

Push -pull

Action

Push -pull

Action