AS2523/4 Analog Telephone IC
Telephone Line Interface and Speaker Phone Circuit
Description
AS2523/24 is a flexible CMOS integrated circuit that incorporates DC and AC line adaptation (DC-mask and synthesized AC-impedance of 1000Ω) as well as a speech circuit with softclipping, line loss compensation and Rx volume control for handset and handsfree operation. It shall act as an a/b-line powered device, which is controlled by a CPU via a serial interface on AS2523 or a standard dialler via a parallel interface on AS2524 and AS2524B.
Key Features
- Line/Speakerphone circuit on a 28-pin CMOS-IC, simple inventory: same die for AS2523/24 and AS2523/24B
- Serial I/F on AS2523, parallel I/F on AS2524
- Enhanced voice switching
- Background noise monitoring
- Tx and Rx gain programmable on AS2523 only
- Digital volume control of Rx signals on AS2523 only
- DC characteristic programmable on AS2523 only
- Dual softclipping in handset mode on AS2523 only
- Dual softclipping in handsfree mode on AS2523 only
- Loudspeaker amplifier for loudhearing and handsfree
- Supply voltage generation for external circuitry
- Automatic line loss compensation on AS2523 / 24B only
- Real and complex impedance selectable by external components
- Side tone adaptation selectable by external components
- Unique EMC performance
- Operating range from 15mA to 100mA (down to 5mA with reduced performance)
- Few external components
- Package
- Available in 28-pin SOIC or die
Applications
The devices are ideal for enhanced handsfree feature phones with CallerID and extended displays. The AS2524 and AS2524B are developed to interface with common Taiwanese dialers.
Block diagram for AS2523/4 Analog Telephone IC
AS2523/24 Telephone Line Interface and Speakerphone Circuit Block Diagram