Application information

LNBH23L

6/25

Doc ID 15335 Rev 4

2.4

PDC optional circuit for DiSEQC™ 1.X applications using

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 Figure 4) connected

output capacitance only when the internal 22 kHz tone is activated. This optional circuit is

2.5

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.

2.6

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

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).

2.7

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).

2.8

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-