AN3115 datasheet(10/28 Pages) STMICROELECTRONICS

10 / 28 page

Block diagram and pin function description

AN3115

10/28

Doc ID 16830 Rev 3

Table 4.

LNBH23L pin description

QFN 5x5

pin n°

Symbol

Name

Pin function

VCC

Supply input

8 to 15 V IC DC-DC power supply

VCC–L

Supply input

8 to 15 V analog power supply

NMos drain

Integrated N-channel Power MOSFET Drain

VUP

Step-up voltage

Input of the linear post-regulator. The voltage on this pin is monitored

by the internal step-up controller to keep a minimum dropout across

the linear pass transistor.

VoRX

LDO output port

Output of the linear post-regulator

VoTX

Output port during

22 kHz tone TX

TX Output to the LNB

SDA

Serial data

Bi-directional data from/to the I²C bus

SCL

Serial clock

Clock from the I²C bus

DSQIN

DiSEqC input

This pin accepts the DiSEqC code from the main microcontroller. The

LNBH23L uses this code to modulate the internally-generated 22 kHz

carrier. Set this pin to ground if not used.

TTX

TTX enable

This pin, as well as the TTX I²C bit of the system register, is used to

control the TTX function enable before starting the 22 kHz tone

transmission. Set this pin floating or to GND if not used.

Reserved

To be connected to GND

PDC

Pull-down control

To be connected to the external NPN transistor base to reduce the 22

kHz tone distortion in case of heavy capacitive load at light output

current. If not used it can be left floating.

EXTM

External

modulation

External Modulation Input acts on VoRX linear regulator output to

superimpose an external 22 kHz signal. Needs DC decoupling to the

AC source. If not used it can be left floating.

P-GND

Power ground

DC-DC converter power ground to be connected directly below the

ePad of the PCB top GND layer.

ePad

On the bottom side of the QFN-32 package. It must be connected with

power ground and to the ground layer through vias to dissipate heat.

A-GND

Analog ground

Analog circuits ground

BYP

Bypass capacitor

Needed for internal preregulator filtering. The BYP pin is intended

only to connect an external ceramic capacitor. Any connection of this

pin to an external current or voltage sources may cause permanent

damage to the device.

ADDR

Address setting

Two I²C bus addresses available by setting the ADDR pin voltage

level.

ISEL

Current selection

The resistor RSEL connected between ISEL and GND defines the

linear regulator current limit threshold by the equation: IMAX

(typ.)=10000/ RSEL.

Reserved

To be left floating. Do not connect to GND

1, 2, 3, 7,

8, 16, 17,

23, 24, 25,

26, 31, 32

N.C.

Not connected

Not internally connected pins

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