DESCRIPTION
For driving a dynamic loudspeaker LS1240A can simply use a decoupling capacitor, thus eliminating the usual transformer. No current limitation is provided on the output stage of LS1240A, so a minimum load DC of 50 Ω is adviced, in series with a proper capacitor. The two tone frequencies generated are switched by an internal oscillator in a fast sequence and made audible across an output amplifier in the loudspeaker, both tone frequencies and the switching frequency can be externally adjusted. PIN CONNECTION (top view) SO8 ORDERING NUMBERS Minidip LS1240A SO8 LS1240AD1 The supply voltage is obtained from the AC ring signal and the circuit is designed so that noise on the line or variations of the ringing signal cannot affect correct operation of the device. July 1998 1/7 LS1240A BLOCK DIAGRAM Figure 1 : Test Circuit. R1 = 2.72 ⋅ 104 f1 ⋅ ( 1 − 0.04 ln ) 1943 f1 (Hz) f2 = 0.725 f1 fSWEEP = 750 C1 (nF) 2/7 LS1240A ABSOLUTE MAXIMUM RATINGS
Symbol VAB VAB DC Top Tstg Parameter C...
STMicroelectronics
