LNBH23L STMicroelectronics, LNBH23L Datasheet - Page 6

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

Application information
2.4
2.5
2.6
2.7
2.8
6/25
V
supply will be always provided to the LNB from the V
PDC optional circuit for DiSEQC™ 1.X applications using
V
In some applications, at light output current (< 50 mA) having heavy LNB output capacitive
load, the 22 kHz tone can be distorted. In this case it is possible to add the "Optional"
external components shown in the typical application circuits (see
between V
output capacitance only when the internal 22 kHz tone is activated. This optional circuit is
not needed in standard applications having I
I²C interface
The main functions of the IC are controlled via I²C bus by writing 6 bits on the system
register (SR 8 bits in write mode). On the same register there are 5 bits that can be read
back (SR 8 bits in read mode) to provide the diagnostic flags of two internal monitoring
functions (OTF, OLF) and three output voltage register status (EN, VSEL, LLC) received by
the IC (see below diagnostic functions section). In read mode there are 3 Test bits (test 1 - 2
- 3) that must be disregarded from the MCU. While, in write mode, 2 test bits (test 4 - 5) must
be always set LOW.
Output voltage selection
When the IC sections are in stand-by mode (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 means of the V
with the LLC I²C bit that increases the selected voltage value to compensate possible
voltage drop along the output line. The LNBH23L is also compliant to the USA LNB power
supply standards. In stand-by condition (EN bit LOW) all the I²C bits and the TTX pin must
be set LOW (if the TTX pin is not used it can be left floating or to GND but the TTX bit must
be set LOW during the stand-by condition).
Diagnostic and protection functions
The LNBH23L has two diagnostic internal functions provided via I²C bus by reading 2 bits on
the system register (SR bits in read mode). the diagnostic bits are, in normal operation (no
failure detected), set to LOW. The diagnostic bits are dedicated to the over-temperature and
over-load protections status (OTF and OLF).
Over-current and short circuit protection and diagnostic
In order to reduce the total power dissipation during an overload or a short circuit condition,
the device is provided with a dynamic short circuit protection. It is possible to set the short
circuit current protection either statically (simple current clamp) or dynamically by the PCL
bit of the I²C SR. When the PCL (pulsed current limiting) bit is set lo LOW, the over current
protection circuit works dynamically: as soon as an overload is detected, the output is shut-
oTX
OTX
internal circuits must be disabled by setting the TTX to LOW. The 13 / 18 V power
signal on to EXTM pin
oRX
and PDC pin. This optional circuit acts as an active pull-down discharging the
SEL
Doc ID 15335 Rev 4
bit (voltage SELect). Additionally, the LNBH23L is provided
OUT
> 50 mA and capacitive load up to 250 nF.
oRX
pin.
Figure
4) connected
LNBH23L