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TEA7088AFP

LOW-RANGE PHONE DEDICATED CHIP

STMicroelectronics 

TEA7088A

SPEECH

The speech network includes :

- a low noise transmit channel suitable for any kind

of microphone transducer. Softclipping on trans-

mit line signal is provided by the chip.

- a low noise receive channel with symmetrical

outputs to be compatible with both piezoceramic

and electrodynamic earpiece. An additional 6dB

gain can be inserted in the receive channel

through software control.

- a line length gain control (AGC) with starting point

of gain regulation fixed at 25mAline current ; slope

of gain regulationis externallyadjustablewith one

resistor.AGC can be removedby hardware (maxi-

mum gain flat) or by software (-2dB flat).

The phone impedance and sidetone can be tuned

through external networks.

DTMF GENERATOR

The onboard DTMF generator fullfils the CEPT

requirements with an external single pole filter.

RINGER

Up to 8 different tones can be generated by the

TEA7088Aringer. The digital volume control of the

ringer can be performed through a specific com-

mand (4 steps). A ring indication signal is provided

to the microcontroller by the TEA7088A.If more

tones are requested the input RM/MSK allows to

inject tones generated by the microcontroller.

FURTHER ADVANTAGES

The microcontroller power supply is provided by the

TEA7088A.The power supply is specifically designed

to copewitha longflash or a long groundkey duration.

The TEA7088A is able to supply the necessary

current to an external speakerphone circuit

TEA7540 and loudspea ker amplifier TEA7532

without any additional circuitry.

Line current and reset indications are provided to

the microcontroller by the TEA7088A.

The microcontroller drives the TEA7088A through

a 2 wires serial interface.

PIN DESCRIPTION

Name

SOFT

RECIN

SN

AGC

MIC1

MIC2

GTR

VCC

GND

IVLS

VS

VL

VMC

GREC

EAR-

EAR+

BUZ

VRING

RES

PON

RI

OSC

MSK

DATA

DCL

VRMC

VREF

DTMF

Pin N°

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

2/17

Description

Transmit Softclipping Time Constant

Receiving Input

Sidetone Network Input

Line Current Regulation Stop Value

Microphone Input

Microphone Input

Transmit Gain Adjustment

Transmit and Receive Part Power Supply

Ground

Line Current Source Power Supply

Voltage Stabilizer

Positive Line

Unregulated Microcontroller Power Supply

Receive Gain Adjustment

Negative Earphone Output

Positive Earphone Output

Ringer Buzzer Output

Ring Power Supply

Reset

Power On

Ring Indicator

Oscillator Input

Mask, Ring Melody Input

Data Input

Data Clock Input

Microcontroller Stabilized Power Supply

Reference Voltage (VCC/2)

DTMF Filter

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