SAN2202a

sames SAN2202 APPLICATION NOTE SINGLE CHIP “SPEAKERPHONE” WITH 8 - OHM LOUDSPEAKER AMPLIFIER 1 Scope This application note describes a low-cost add-on circuit for driving an 8Ω-Loudspeaker to get a simple loudhearing (“Speakerphone”) Telephone. To possible ways of supplying the amplifier are shown: SAN2202a: SAN2202b: Amplifier supply in shunt transistor path Amplifier supply by power extraction circuit (SAN3020) It can be added to any SA253x application without interfering with PTT-relevant parameters, like AC-impedance, Sidetone cancellation or DC-mask. 2 Key Features Low cost additional circuit enables use of loudhearing function Full duplex “handsfree” operation via handset microphone and loudspeaker (at distances <2m between telephone and user) Can be added to any SA253x- application Enables use of low cost 8Ω - Loudspeaker High output power with low distortion Entirely powered from the telephone line No influence of loudspeaker amplifier in AC-impedance, sidetone cancellation or DC-mask Loudspeaker volume adjustable by potentiometer Excellent sidetone cancellation of SAS253x circuits enables high loudspeaker volume without howling between handset microphone and loudspeaker SAN2202 PDS038-SA2531/2-001 Rev. B 21-03-00 SAN2202 TABLE OF CONTENTS 1 SCOPE.......................................................................................................................................................................................................