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 analog telephone line.

AS2540 can operate in a so-called main power 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*#).

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)
• Watchdog timer for Backup Mode
• Additional input for modem transmit path
• Additional output for modem receive path
• CMOS for high EMC immunity
• Low Noise (maximum –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

Applications

• Web Telephones
• Answering Machines
• Fax Machines
• Base Station of Cordless Telephones
• Hospital Communication Units

Block diagram for AS2540 Analog Telephone