austriamicrosystems Telephone Line Interface and Speakerphone Circuit DATA SHEET AS2523, AS2524, AS2524B Key Features General Description - Line/Speakerphone circuit on a 28-pin CMOS-IC, simple AS2523/24 is a CMOS integrated circuit that incorporates inventory: same die for AS2523/24 and AS2523/24B DC and AC line adaptation (DC-mask and synthesized AC- - Serial I/F on AS2523, parallel I/F on AS2524 impedance of 1000 ) as well as a speech circuit with - Enhanced voice switching softclipping, line loss compensation and Rx-volume control - Background noise monitoring for handset and handsfree operation. It shall act as an a/b- - Tx- and Rx-gain programmable on AS2523 only line powered device, which is controlled by a CPU via a - Digital volume control of Rx signals on AS2523 only serial interface on AS2523 or a standard dialler via a - DC characteristic programmable on AS2523 only parallel interface on AS2524 and AS2524B. - Dual softclipping in handset mode on AS2523 only - Dual softclipping in handsfree mode on AS2523 only - Loudspeaker amplifier for loudhearing and handsfree Applications - Supply voltage generation for external circuitry Enhanced handsfree feature phones with CallerID and - Automatic line loss compensation on AS2523 / 24B only extended displays. The AS2524 and AS2524B are - Real and complex impedance selectable by external developed to interface with common Taiwanese dialers. components - Side tone adaptation selectable by external components - Unique EMC performance Package - Operating range from 15mA to 100mA (down to 5mA Available in 28-pin SOIC or die with reduced performance) - Few external components Block Diagram Revision 1.13 Page 1 of 19 Data Sheet AS2523, AS2524, AS2524B austriamicrosystems Pin description Pin Symbol Function 15 LS Line Current Sense Input Analog input for sensing the line current 12 LI Line Input Analog input used for power extraction and line current sensing 13 RI Receive Input Analog input for ac-separated receive signal 9 STB Side Tone Balance Input Analog input for side tone cancellation network 10 CS Current Shunt Control Output N-channel open drain output to control the external high power shunt transistor for synthesizing AC- and DC-impedance, modulation of line voltage and shorting the line during make periods of pulse dialing 16 CI Complex Impedance Input Analog input pin for the capacitor to program a complex impedance 14 SS Supply Source Control Output N-channel open drain output to control the external high power source transistor for supplying (Vpp) the loudspeaker amplifier in off-hook loudspeaking/handsfree mode 11 VSS Voltage Source Source Negative Analog Power Supply 18 VDD Voltage Drain Drain Positive Analog Power Supply 19 AGND Analog Ground Special ground for the internal amplifiers 8 M1 Microphone Input 1 Differential input for the handset microphone (electret) 6 M2 Microphone Input 2 Differential input for the handset microphone (electret) 7 M3 Microphone Input 3 Differential input for the handsfree microphone (electret) 5 M4 Microphone Input 4 Differential input for the handsfree microphone (electret) 17 RO Receive Output to Handset Output for driving a dynamic earpiece with an impedance from 150 to 300 Revision 1.13 Page 2 of 19