LNBH221 datasheet(15/27 Pages) STMICROELECTRONICS

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LD39150

LNBH221 software description (same for both section)

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6.5

Power-On I2C interface reset

The I2C interface built in the LNBH221 is automatically reset at power-on. As long as the

VCC stays below the UnderVoltage Lockout threshold (6.7V typ.), the interface will not

respond to any I2C command and the System Register (SR) is initialized to all zeroes, thus

keeping the power blocks disabled. Once the VCC rises above 7.3V typ, the I

2C interface

becomes operative and the SR can be configured by the main µP. This is due to 500mV of

hysteresis provided in the UVL threshold to avoid false retriggering of the Power-On reset

circuit.

6.6

Address Pin

Connecting this pin to GND the Chip I2C interface address is 0001000, but, it is possible to

choice among 4 different addresses simply setting this pin at 4 fixed voltage levels (see

Table 7. on page 17).

6.7

DiSEqCTM Implementation

The LNBH221 helps the system designer to implement the bi-directional DiSEqC 2.0

protocol by allowing an easy PWK modulation/demodulation of the 22KHz carrier. The PWK

data are exchanged between the LNBH221 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

LNBH221. 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

VOUT pins of the LNBH221, as shown in the Typical Application Circuit on page 7, 8. To

avoid any losses due to the R-L impedance during the tone transmission, the LNBH221 has

dedicated output (VOTX) that, in a DiSEqC 2.0 application, is connected after the filter and

must be enabled by setting the TTX SR bit HIGH only during the tone transmission (see

DiSEqC 2.O operation description on page 9).

Unidirectional (1.x) DiSEqC and non-DiSEqC systems normally don't need this termination,

and the VOTX pin can be directly connected to the LNB supply port of the Tuner (see

DiSeqC 1.x application circuit on pag. 7, 8). There is also no need of Tone Decoding, thus

DETIN and DSQOUT pins can be left unconnected and the Tone is provided by the VOTX.

LNBH221 Datasheet(PDF) 15 Page - STMicroelectronics