Datasheet

Application information LNBH25L
6/28 Doc ID 022634 Rev 2
2.3 Data encoding by external DiSEqC™ envelope control
through the DSQIN pin
If an external DiSEqC envelope source is available, it is possible to use the internal 22 kHz
generator activated during the tone transmission by connecting the DiSEqC envelope
source to the DSQIN pin. In this case the I²C tone control bits must be set: EXTM = 0 and
TEN = 1. In this way, the internal 22 kHz signal is superimposed to the V
OUT
DC voltage to
generate the LNB output 22 kHz tone. During the period in which the DSQIN is kept HIGH,
the internal control circuit activates the 22 kHz tone output.
The 22 kHz tone on the V
OUT
pin is activated with about 6 µs delay from the DSQIN TTL
signal rising edge, and it stops with a delay time in the range from 15 µs to 60 µs after the 22
kHz TTL signal on DSQIN has expired (refer to
Figure 3 ).
Figure 3. Tone enable and disable timing (using envelope signal)
2.4 Output current limit selection
The linear regulator current limit threshold can be set by an external resistor connected to
the ISEL pin. The resistor value defines the output current limit by the equation:
Equation 1
where RSEL is the resistor connected between ISEL and GND expressed in kΩ and
I
MAX
(typ.) is the typical current limit threshold expressed in mA. I
MAX
can be set up to
750 mA.
2.5 Output voltage selection
The linear regulator output voltage level can be easily programmed in order to accomplish
application specific requirements, using 4 bits of an internal DATA1 register (see
Section 7.3
and
Ta bl e 13 for exact programmable values). Register writing is accessible via the I²C bus.
AM10427v1
~ 6 µs
15 µs ~ 60 µs
DSQIN
Tone
Output
111.1
MAX
RSEL
13915
.)typ(I
=