LNBH26PQR datasheet(6/38 Pages) STMICROELECTRONICS

6 / 38 page

Application information (valid for each section A/B)

LNBH26

6/38

Doc ID 022771 Rev 1

Figure 2.

Tone enable and disable timing (using external waveform)

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 on the VOUT 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 VOUT pin is activated with a delay of about 6 µs from DSQIN TTL

signal rising edge, and it stops with a delay time in the range of 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

LPM (low power mode)

In order to reduce total power loss, each section of the LNBH26 is provided with the LPM I²C

bit that can be activated (LPM=1) in applications where the 22 kHz tone can be disabled for

long time periods. The LPM bit can be set to “1” when the DiSEqC™ data transmission is

not requested (no 22 kHz tone output is present); in this condition the drop voltage across

the integrated LDO regulator (VUP - VOUT) is reduced to 0.6 V typ. and, consequently, the

power loss inside the relative LNBH26 channel regulator is reduced too. For example, at 500

mA load, LPM=1, allowing a minimum LDO dissipated power of 0.3 W typ. It is

recommended to set the LPM bit to “0” before starting the 22 kHz DiSEqC™ data

transmission; in this condition the drop voltage across the LDO is kept to 1 V typ. Keep

LPM=0 at all times in case the LPM function is not used.

2.5

DISEQC™ 2.0 implementation

The built-in 22 kHz tone detector completes the fully bi-directional DiSEqC™ 2.0 interfacing.

Each LNBH26 section DETIN pin must be AC coupled to the DiSEqC™ bus, and extracted

PWK data is available on the corresponding DSQOUT pin. To comply with the bi-directional

DiSEqC™ 2.0 bus hardware requirements, an output R-L filter is needed (per each voltage

AM10426v1

~ 1 µs

~ 60 µs

DSQIN

Tone

Output

AM10427v1

~ 6 µs

15 µs ~ 60 µs

DSQIN

Tone

Output

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