LNBH25 datasheet(7/34 Pages) STMICROELECTRONICS

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LNBH25

Application information

Doc ID 022433 Rev 4

7/34

requirements an output RL filter is needed. In order to avoid 22 kHz waveform distortion

during tone transmission, LNBH25 is provided with the BPSW pin to be connected to an

external transistor, which allows to bypass the output RL filter in DiSEqC 2.x applications

while in transmission mode. Before starting tone transmission by means of the DSQIN pin,

make sure that the TEN bit is preventively set to “1” and after ending tone transmission,

make sure that the TEN bit is set to “0”.

2.6

Output current limit selection

The linear regulator current limit threshold can be set by an external resistor connected to

the ISEL pin. The resistor value defines the output current limit by the equation:

Equation 1

with ISET=0

Equation 2

with ISET=1

(Refer also to the ISET bit description in

Table 9).

where RSEL is the resistor connected between ISEL and GND expressed in k

Ω and

IMAX(typ.) is the typical current limit threshold expressed in mA. IMAX can be set up to 1 A.

2.7

Output voltage selection

The linear regulator output voltage level can be easily programmed in order to accomplish

application specific requirements, using 4 bits of an internal DATA 1 register (see

7.3: Data

registers and Table 14 for exact programmable values). Register writing is accessible via the

I²C bus.

2.8

Diagnostic and protection functions

LNBH25 has 8 diagnostic internal functions provided via the I²C bus, by reading 8 bits on

two STATUS registers (in read mode). All the diagnostic bits are, in normal operation (that is

no failure detected), set to LOW. Two diagnostic bits are dedicated to the overtemperature

and overload protection status (OTF and OLF) while the remaining 6 bits are dedicated 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 VOUT pin (PDO), to the

input voltage Power Not Good function (PNG) and to the 22 kHz tone presence on the

DETIN pin (TDET). Once the OLF (or OTF or PNG) bit has been activated (set to “1”), it is

latched to “1” until relevant cause is removed and a new register reading operation is done.

111

MAX

RSEL

13915

typ

(

068

MAX

RSEL

6808

typ

(

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