LNBH23L STMicroelectronics, LNBH23L Datasheet - Page 5

• Manufacturer Part Number: LNBH23L
• Description: LNB supply and control IC with step-up and I2C interface
• Manufacturer: STMicroelectronics

LNBH23L
2
Note:
2.1
2.2
2.3
Application information
This IC has a built-in DC-DC step-up converter that, from a single source from 8 V to 15 V,
generates the voltages (V
dissipated power of 0.55 W typ. @ 500 mA load (the linear post-regulator drop voltage is
internally kept at V
whole circuit when the supplied V
In this document the V
output (V
DiSEqC™ data encoding
The internal 22 kHz tone generator is factory trimmed in accordance to the standards, and
can be selected by I²C interface TTX bit (or TTX pin) and activated by a dedicated pin
(DSQIN) that allows immediate DiSEqC™ data encoding, or through TEN I²C bit in case the
22 kHz presence is requested in continuous mode. In stand-by condition (EN bit LOW) The
TTX function must be disabled setting TTX to LOW. Besides the internal 22 kHz tone
generator, the auxiliary modulation pin (EXTM) can be driven by an external 22 kHz source
and in this case TTX must be set to low.
DiSEqC™ 1.X implementation by EXTM pin
In order to improve design flexibility and reduce the total application cost, an analogic
modulation input pin is available (EXTM) to generate the 22 kHz tone superimposed to the
V
modulating signal source to the EXTM pin. If the EXTM solution is used the output R-L filter
can be removed (see
used keep TTX set to low.
The pin EXTM modulates the V
V
Where V
EXTM pins while G
DiSEqC™ 1.X implementation with V
connection
If an external 22 kHz tone source is not available, it is possible to use the internal 22 kHz
tone generator signal available through the V
internal circuit must be preventively set ON by setting the TTX function to High. This can be
controlled both through the TTX pin or by I²C bit. By this way the V
superimposed to the V
Figure
V
bit.The DSQIN internal circuit activates the 22 kHz tone on the V
25 µs delay from the TTL signal presence on the DSQIN pin, and it stops with 1 cycles ± 25
µs delay after the TTL signal is expired. As soon as the tone transmission is expired, the
oRX
oRX(AC)
oTX
pin can be activated during the 22 kHz transmission either by DSQIN pin or by the TEN
DC output voltage. An appropriate DC blocking capacitor must be used to couple the
3). After TTX is set to High the internal 22 kHz tone generator available through the
oRX(AC)
oRX
= V
EXTM(AC)
pin).
and V
UP
EXTM
- V
Figure
x G
EXTM(AC)
OUT
oRX
OUT
is the voltage gain from EXTM to V
EXTM
UP
DC voltage to generate the LNB output 22 kHz tone (see
is intended as the voltage present at the linear post-regulator
) that let the linear post-regulator to work at a minimum
= 1.1 V typ.). An under voltage lockout circuit will disable the
5) saving the external components cost. If this configuration is
Doc ID 15335 Rev 4
oRX
are, respectively, the peak to peak voltage on the V
CC
voltage through the series decoupling capacitor, so that:
drops below a fixed threshold (6.7 V typically).
oTX
pin to drive the EXTM pin. The V
OTX
oRX
and EXTM pin
.
oTX
Application information
oTX
output with 0.5 cycles ±
22 kHz signal will be
oTX
oRX
pin
and
5/25