LNBH26 datasheet(7/38 Pages) STMICROELECTRONICS

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LNBH26

Application information (valid for each section A/B)

Doc ID 022771 Rev 1

7/38

output pin). In order to avoid 22 kHz waveform distortion during tone transmission, each

LNBH26 section is provided with a BPSW pin to be connected to an external transistor,

which allows the bypassing of the corresponding output RL filter in DiSEqC 2.x applications

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

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

that the TEN bit is set to “0”.

2.6

Output current limit selection

The linear regulators 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 for

each channel. However, it is recommended to not exceed, for a long period, a total amount

of current of 1 A from both sections (IOUT_A + IOUT_B < 1 A) in order to avoid the

overtemperature protection triggering and to thoroughly validate the PCB layout thermal

management in real application environment conditions.

2.7

Output voltage selection

Each linear regulator channel output voltage level can be easily programmed in order to

accomplish application specific requirements, using 4 + 4 bits of an internal DATA1 register

(see

Section 7.3: Data registers and Table 14: Output voltage selection table (Data1

I²C bus.

2.8

Diagnostic and protection functions

The LNBH26 has 14 diagnostic internal functions provided via the I²C bus, by reading 14

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

(that is, no failure detected), set to LOW. One diagnostic bit is dedicated to the

overtemperature status (OTF), one bit is dedicated to the input voltage power not good

function (PNG), while the remaining 12 bits (6 per channel) are dedicated to the overload

206

MAX

RSEL

16578

typ

(

159

MAX

RSEL

6452

typ

(

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