lnbh221 STMicroelectronics, lnbh221 Datasheet - Page 9

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

LD39150
5
Application information
Basically, the LNBH221 includes two circuits that are completely independent. Each circuit
can be separately controlled and must have its independent external components. All the
below specification must be considered equal for each section.
This IC has a built in DC/DC step-up controller that, from a single supply source ranging
from 8 to 15V, generates the voltages (V
minimum dissipated power of 1W typ. @ 500mA load (the linear regulator drop voltage is
internally kept at: V
whole circuit when the supplied V
internal 22KHz tone generator is factory trimmed in accordance to the standards, and can
be controlled either by the I
immediate DiSEqC
HIGH, a continuous 22KHz tone is generated on the output regardless of the DSQIN pin
logic status.
The TEN bit must be set LOW when the DSQIN pin is used for DiSEqC
fully bi-directional DiSEqC
detector. Its input pin (DETIN) must be AC coupled to the DiSEqC
PWK data are available on the DSQOUT pin (*). To comply to the bi-directional DiSEqC
2.0 bus hardware requirements an output R-L filter is needed. The LNBH221 is provided
with two output pins: the V
used when the tone is received. This allows the 22KHz Tone to pass without any losses due
to the R-L filter impedance (see DiSeqC 2.0 application circuit on page 4). In DiSeqC 2.0
applications during the 22KHz transmission activated by DSQIN pin (or TEN I
V
supply and the 22KHz tone, are provided by mean of V
transmission is expired, the V
the 13/18V power supply is provided to the LNB by the V
When the LNBH221 is used in DiSeqC 1.x applications the R-L filter is not required (see
DiSeqC 1.x application circuit on pag. 4), the TTX I
that, the V
enabled by DSQIN pin or by TEN I
bus by writing 6 bits on the System Register (SR, 8 bits). The same register can be read
back, and two bits will report the diagnostic status. When the IC is put in Stand-by (EN bit
LOW), the power blocks are disabled.
When the regulator blocks are active (EN bit HIGH), the output can be logic controlled to be
13 or 18V by mean of the VSEL bit (Voltage SELect) for remote controlling of non-DiSEqC
LNBs. Additionally, the LNBH221 is provided with the LLC I
voltage value (+1V when VSEL=0 and +1.5V when VSEL=1) to compensate for the excess
voltage drop along the coaxial cable (LLC bit HIGH). By mean of the LLC bit, the LNBH221
is also compliant to the American LNB power supply standards that require the higher
output voltage level to 19.5V (typ.) (instead of 18V), by simply setting the LLC=1 when
VSEL=1. In order to improve design flexibility and to allow implementation of newcoming
LNB remote control standards, an analogic modulation input pin is available (EXTM).
An appropriate DC blocking capacitor must be used to couple the modulating signal source
to the EXTM pin. Also in this case, the V
transmission by setting the TTX bit high. When external modulation is not used, the relevant
pin can be left open. The current limitation block is SOA type: if the output port is shorted to
ground, the SOA current limitation block limits the short circuit current (I
300mA or 200mA respectively for V
O
TX pin must be preventively set ON by the TTX I
O
TX output pin can provide both the 13/18V power supply and the 22KHz tone,
TM
UP
data encoding (*). When the TEN (Tone ENable) I
-V
OUT
O
TM
TX to be used during the tone transmission and the V
=2V typ.). An UnderVoltage Lockout circuit will disable the
O
2
C
TX must be set to OFF by setting the TTX I
2.0 interfacing is completed by the built-in 22KHz tone
TM
2
CC
C bit. All the functions of this IC are controlled via I
interface or by a dedicated pin (DSQIN) that allows
OUT
drops below a fixed threshold (6.7V typically). The
UP
13V or 18V, to reduce the power dissipation.
) that let the linear post-regulator to work at a
O
TX output must be set ON during the tone
2
C bit must be kept always to HIGH so
2
C bit and, both the 13/18V power
O
TX output. As soon as the tone
2
O
C bit that increase the selected
RX pin through the R-L filter.
TM
Application information
bus, and the extracted
TM
2
2
C bit to zero and
C bit it is set to
SC
encoding. The
) at typically
2
C bit), the
O
RX to be
2
C
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TM
TM