E-LS1240A Datasheet, PDF (2/9 Pages) STMicroelectronics – Low current consumption, in order to allow the parallel operation of 4 devices

Block diagram and test circuit
1
Block diagram and test circuit
Figure 1. LS1240 block diagram
Telephone
line
8
Rectifier
capacitor
7
N.C.
6
Rectifier
bridge
+
Threshold circuit
with hysteresis
-
Buzzer
5
Output
stage
LS1240
Switching
frequency
) _generator
ct(s ₁
du Telephone
ro ^line
2
GND
3
Sweep rate
control capacitor
te ^P _{Figure 2. Test circuit}
Tone frequency
generator
4
Output frequency
control resistor
Obsolete ^{Product(s) - Obsole} _R1
=
2.72 ⋅ 10⁴
f1 (Hz)
⋅
(1
−
0.04
ln
19f143⁾
f2 = 0.725 f1
f_SWEEP
=
750
C1 (nF)
2/9