Data Sheet AS2540

Revision 3.1

Page 1 of 18

General Description

The AS2540 is a CMOS integrated circuit that

incorporates a speech circuit (line-adaptation, 2/4-wire

conversion, separate Rx- and Tx-amplifiers for handset

and modem), MF dialler, ring frequency detector, ring

melody generator and a two wire serial interface. It

shall act as an a/b-line-powered device in order to

interface a main-powered CPU to the analogue

telephone line.

AS2540 can operate in a so-called mainpower mode

and in a backup mode. During mainpower mode, a

watchdog timer is running on AS2540, which has to be

reset via the serial interface, which is connected to the

CPU through opto-couplers. During backup mode (=

The main-power failure or SW engine problem),

AS2540 can operate as an independent basic MF

dialler (digits 0-9*#)

Applications

-

Web Telephones

-

Answering Machines

-

Fax Machines

-

Base Station of Cordless Telephones

-

Hospital Communication Units

Key Features

-

Line Interface, Speech Circuit, MF Dialler and Tone Ringer

on a 28 pin CMOS chip

-

Programmable via 2-wire serial interface

(UART 9600 baud, 8N1)

-

Watch dog timer for Backup Mode

-

Additional input for modem transmit path

-

Additional output for modem receive path

-

CMOS for high EMC immunity

-

Low Noise (max. –72 dBm)

-

Operating range from 15mA to 100mA (down to 5mA with

reduced performance)

-

Soft clipping for handset operation to avoid harsh distortion

-

Line loss compensation selectable by pin option

-

Real and complex impedance selectable by external

components

-

Side tone adaption selectable by external components

-

Ring frequency discrimination

-

3-tone ring melody generator

Package

-

28 pin SOIC

-

Dice-on-Foil

Block Diagram

LS

ROH

ROT

M1

M2

TIT

AGND

Line

LI

RI

STB

CS

CI

DPn

C1

C2

C3

R1

R2

MODE

RFD

-2d B

+6dB

+2d B

Mask

DTMF-

generator

DIALLER

UART

MO

RxD

TxD

VDD

EHS

MHS

VSS

OSC

Main Power Mode

LS

ROH

ROT

M1

M2

TIT

AGND

Line

LI

RI

STB

CS

CI

DPn

C1

C2

C3

R1

R2

MODE

RFD

-2dB

+6dB

+2d B

Mask

DTMF-

generator

DIALLER

UART

MO

RxD

TxD

VDD

EHS

MHS

VSS

OSC

Backup Mode

Remote Controlled Single-Chip-Telephone

AS2540

DATA SHEET (PRELIMINARY)