2

Application information (valid for each section A/B)

can be separately controlled and have their independent external components. All the specifications below must

be considered equal for both sections (A/B).

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

DiSEqC™ tone) work with a minimum dissipated power of 0.5 W typ. @ 500 mA load (the LDO drop voltage is

output is disabled by setting the LPM bit to “1” (see LPM function description). The IC is also provided with an

(4.7 V typ.). The step-up converter soft-start function reduces the in-rush 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”.

Each of the above solutions requires that during the 22 kHz tone activation and/or DiSEqC™ data transmission,

the LPM bit must be set to “0” see Section 2.4 LPM (low power mode).

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”.

tone generator.

The output tone waveforms are internally controlled by the LNBH26S 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 LNBH26S activates the 22

after the 22 kHz TTL signal on DSQIN has expired, refer to Figure 2. Tone enable and disable timing (using

external waveform).

~ 1 µs

~ 60 µs

DSQIN

Tone

output

GIPG2601151219LM

LNBH26S

Application information (valid for each section A/B)

DS8975 - Rev 5

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