LNBH2 STMicroelectronics, LNBH2 Datasheet - Page 5

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

APPLICATION INFORMATION
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
1.65W typ. @ 750mA load (the linear regulator drop voltage is internally kept at: V
UnderVoltage Lockout circuit will disable the whole circuit when the supplied V
threshold (6.7V typically). The internal 22KHz tone generator is factory trimmed in accordance to the
standards, and can be controlled either by the I
immediate DiSEqC
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
bi-directional DiSEqC
(DETIN) must be AC coupled to the DiSEqC
DSQOUT pin (*).
To comply to the bi-directional DiSEqC
The LNBH21 is provided with two output pins: the V
V
to the R-L filter impedance (see DiSeqC 2.0 application circuit on page 5). In DiSeqC 2.0 applications
during the 22KHz transmission activated by DSQIN pin (or TEN I
preventively set ON by the TTX I
provided by mean of V
OFF by setting the TTX I
pin through the R-L filter. When the LNBH21 is used in DiSeqC 1.x applications the R-L filter is not
required (see DiSeqC 1.x application circuit on pag.5), the TTX I
that, the V
DSQIN pin or by TEN I
All the functions of this IC are controlled via I
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 18 V by mean of the V
remote controlling of non-DiSEqC LNBs.
Additionally, the LNBH21 is provided with the LLC I
when V
cable (LLC bit HIGH).
By mean of the LLC bit, the LNBH21 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
V
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
must be set ON during the tone 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 and it is possible to select two current limit thresholds, by the
dedicated I
connected a voltage > 3.3V. The lower threshold is in the range of 450mA to 700mA when the I
connected to ground. When the output port is shorted to ground, the SOA current limitation block limits the
short circuit current (I
dissipation. Moreover, it is possible to set the Short Circuit Current protection either statically (simple
current clamp) or dynamically by the PCL bit of the I
set to LOW, the overcurrent protection circuit works dynamically, as soon as an overload is detected, the
output is shut-down for a time T
is set to HIGH. After this time has elapsed, the output is resumed for a time T
end of T
the end of a full T
reset to LOW. Typical T
operation can greatly reduce the power dissipation in short circuit condition, still ensuring excellent
power-on start up in most conditions.
O
SEL
RX to be used when the tone is received. This allows the 22KHz Tone to pass without any losses due
=1.
SEL
ON
O
, if the overload is still detected, the protection circuit will cycle again through T
=0 and +1.5V when V
SEL
TX output pin can provide both the 13/18V power supply and the 22KHz tone, enabled by
pin. The higher threshold is in the range of 750mA to 1A if the I
ON
TM
SC
in which no overload is detected, normal operation is resumed and the OLF bit is
TM
O
2
data encoding (*). When the TEN (Tone ENable) I
) at typically 400mA or 200mA respectively for V
C bit.
TX output. As soon as the tone transmission is expired, the V
ON
2
2.0 interfacing is completed by the built-in 22KHz tone detector. Its input pin
C bit to zero and the 13/18V power supply is provided to the LNB by the V
UP
+T
) that let the linear post-regulator to work at a minimum dissipated power of
OFF
OFF
SEL
time is 990ms and it is determined by an internal timer. This dynamic
2
C bit and, both the 13/18V power supply and the 22KHz tone, are
, typically 900ms. Simultaneously the OLF bit of the System Register
=1) to compensate for the excess voltage drop along the coaxial
TM
2.0 bus hardware requirements an output R-L filter is needed.
2
TM
C TM bus by writing 6 bits on the System Register (SR, 8
2
C
bus, and the extracted PWK data are available on the
TM
O
2
2
C SR; when the PCL (Pulsed Current Limiting) bit is
TX to be used during the tone transmission and the
C bit that increase the selected voltage value (+1V
interface or by a dedicated pin (DSQIN) that allows
2
C bit must be kept always to HIGH so
O
2
C bit), the V
13V or 18V, to reduce the power
2
SEL
C bit it is set to HIGH, a
ON
TM
=1/10T
CC
bit (Voltage SELect) for
UP
SEL
drops below a fixed
encoding. The fully
O
-V
O
TX must be set to
TX pin must be
is left floating or
OFF
O
OFF
=2.2V typ.). An
(typ.). At the
and T
O
LNBH21
TX output
SEL
ON
pin is
O
5/20
. At
RX