lnbh221 STMicroelectronics, lnbh221 Datasheet - Page 15

• Manufacturer Part Number: lnbh221
• Description: Dual Lnb Supply And Control Ic With Step-up Converter And I2c Interface
• Manufacturer: STMicroelectronics

LD39150
6.5
6.6
6.7
Power-On I
The I
V
respond to any I
keeping the power blocks disabled. Once the V
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.
Address Pin
Connecting this pin to GND the Chip I
choice among 4 different addresses simply setting this pin at 4 fixed voltage levels (see
Table 7.
DiSEqC
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
V
avoid any losses due to the R-L impedance during the tone transmission, the LNBH221 has
dedicated output (V
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 V
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 V
CC
OUT
stays below the UnderVoltage Lockout threshold (6.7V typ.), the interface will not
2
pins of the LNBH221, as shown in the Typical Application Circuit on page 7, 8. To
C interface built in the LNBH221 is automatically reset at power-on. As long as the
on page 17).
O
TM
TX pin can be directly connected to the LNB supply port of the Tuner (see
Implementation
2
2
C command and the System Register (SR) is initialized to all zeroes, thus
C interface reset
O
TX) that, in a DiSEqC 2.0 application, is connected after the filter and
LNBH221 software description (same for both section)
2
C interface address is 0001000, but, it is possible to
CC
rises above 7.3V typ, the I
2
C interface
O
15/27
TX.