LNBH2 STMicroelectronics, LNBH2 Datasheet - Page 9

• Manufacturer Part Number: LNBH2
• Description: LNB SUPPLY AND CONTROL IC WITH STEP-UP CONVERTER AND I2C INTERFACE
• Manufacturer: STMicroelectronics

LNBH21
DiSEqCTM IMPLEMENTATION
The LNBH21 helps the system designer to implement the bi-directional (2.0) DiSEqC protocol by allowing
an easy PWK modulation/demodulation of the 22KHz carrier. The PWK data are exchanged between the
LNBH21 and the main µP using logic levels that are compatible with both 3.3 and 5V microcontrollers.
This data exchange is made through two dedicated pins, DSQIN and DSQOUT, in order to maintain the
timing relationships between the PWK data and the PWK modulation as accurate as possible. These two
pins should be directly connected to two I/O pins of the µP, thus leaving to the resident firmware the task
of encoding and decoding the PWK data in accordance to the DiSEqC protocol. Full compliance of the
system to the specification is thus not implied by the bare use of the LNBH21. The system designer should
also take in consideration the bus hardware requirements; that can be simply accomplished by the R-L
termination connected on the V
pins of the LNBH21, as shown in the Typical Application Circuit on page
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4. To avoid any losses due to the R-L impedance during the tone transmission, the LNBH21 has
dedicated output (V
TX) that, in a DiSEqC 2.0 application, is connected after the filter and must be
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enabled by setting the TTX SR bit HIGH only during the tone transmission (see DiSEqC 2.O operation
description on page 2).
Unidirectional (1.x) DiSEqC and non-DiSEqC systems normally don't need this termination, and the V
TX
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pin can be directly connected to the LNB supply port of the Tuner (see DiSeqC 1.x application circuit on
pag.4). There is also no need of Tone Decoding, thus DETIN and DSQOUT pins can be left unconnected
and the Tone is provided by the V
TX.
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