LNBH26 STMicroelectronics, LNBH26 Datasheet - Page 8

• Manufacturer Part Number: LNBH26
• Description: Dual LNB supply and control IC with step-up and I2C interface
• Manufacturer: STMicroelectronics

Application information (valid for each section A/B)
2.9
2.10
2.11
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protection status (OLF), to the output voltage level (VMON), to 22 kHz tone characteristics
(TMON), to the minimum load current (IMON), to external voltage source presence on the
V
the OTF or PNG) bit has been activated (set to “1”), it is latched to “1” until the relevant
cause is removed and a new register reading operation is done.
Surge protections and TVS diodes
Each LNBH26 device section is directly connected to the antenna cable in a set-top box.
Atmospheric phenomenon can cause high voltage discharges on the antenna cable causing
damage to the attached devices. Surge pulses occur due to direct or indirect lightning
strikes to an external (outdoor) circuit. This leads to currents or electromagnetic fields
causing high voltage or current transients. Transient voltage suppressor (TVS) devices are
usually used, as shown in the following schematic (
output circuits where the LNBH26 and other devices are electrically connected to the
antenna cable.
Figure 4.
For this purpose we recommend the use of LNBTVSxx surge protection diodes specifically
designed by ST. The selection of the LNBTVS diode should be made based on the
maximum peak power dissipation that the diode is capable of supporting (see the LNBTVS
datasheet for further details).
FLT: Fault FLAG
In order to get an immediate feedback on a diagnostic status, the LNBH26 is equipped with
a dedicated fault flag pin (FLT). In the case an overload (OLF bit=1), overheating (OTF bit=1)
or power not good (PNG bit=1) condition is detected, the FLT pin (open drain output) is set
to low and is kept low until the relevant activating diagnostic bit is cleared. Be aware that
diagnostic bits OLF, OTF and PNG, once activated, are kept latched to “1” until the origin
cause is removed and a new register reading operation is performed by the microprocessor.
The FLT pin must be connected to a positive voltage (5 V max.) by means of a pull-up
resistor.
VMON: output voltage diagnostic
When one device output voltage is activated (V
and, as long as the output voltage level is below the guaranteed limits, the relevant VMON
I²C bit is set to “1” (see
OUT
pin (PDO), and to 22 kHz tone presence on the DETIN pin (TDET). Once the OLF (or
Surge protection circuit
Table 17
Doc ID 022771 Rev 1
for more details).
OUT
Figure 4
pin), its value is internally monitored
), to protect each section of STB
LNBH26