MC34017AD 데이터 시트보기 (PDF) - Freescale Semiconductor
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MC34017AD Datasheet PDF : 16 Pages
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TYPICAL APPLICATIONS
INTRODUCTION
TYPICAL APPLICATIONS
INTRODUCTION
The 34017A Tone Ringer derives its power supply by
rectifying the AC ringing signal. It uses this power to activate
a tone generator and drive a piezo-ceramic transducer. The
tone generation circuitry includes a relaxation oscillator and
frequency dividers which produce high and low frequency
tones as well as the tone warble frequency. The relaxation
oscillator frequency fO is set by resistor R2 and capacitor C2
connected to Terminal RC. The oscillator will operate with fO
from 1.0 kHz to 10 kHz with the proper choice of external
components (see Figure 2).
The frequency of the tone ringer output signal at RO1 and
RO2 alternates between fO/4 to fO/5. The warble rate at which
the frequency changes is fO/320 for the 34017A-1, fO/640 for
the 34017A-2 and fO/160 for the 34017A-3. With a 4.0 kHz
oscillator frequency, the 34017A-1 produces 800 Hz and
1000 Hz tones with a 12.5 Hz warble rate. The 34017A-2
generates 1600 Hz and 2000 Hz tones with a similar 12.5 Hz
warble frequency from an 8.0 kHz oscillator frequency. The
34017A-3 will produce 400 Hz and 500 Hz tones with a
12.5 Hz warble rate from a 2.0 kHz oscillator frequency. The
tone ringer output circuit can source or sink 20 mA with an
output voltage swing of 37 V peak-to-peak. Volume control is
readily implemented by adding a variable resistance in series
with the piezo transducer.
Input signal detection circuitry activates the tone ringer
output when the AC line voltage exceeds programmed
threshold level. Resistor R3 determines the ringing signal
amplitude at which an output signal at RO1 and RO2 will be
generated. The AC ringing signal is rectified by the internal
diode bridge. The rectified input signal produces a voltage
across R3 which is referenced to RG. The voltage across
resistor R3 is filtered by capacitor C3 at the input to the
threshold circuit.
Figure 4. Oscillator Period (1/fO) versus Oscillator R2 C2
Product
When the voltage on capacitor C3 exceeds 1.2 V, the
threshold comparator enables the tone ringer output. Line
transients produced by pulse dialing telephones do not
charge capacitor C3 sufficiently to activate the tone ringer
output.
Capacitors C1 and C4 and resistor R1 determine the 10 V,
24 Hz signature test impedance. C4 also provides filtering for
the output stage power supply to prevent droop in the square
wave output signal. Six diodes in series with the rectifying
bridge provide the necessary non-linearity for the 2.5 V,
24 Hz signature tests.
An internal shunt voltage regulator between the RI and RG
terminals provides DC voltage to power the output stage,
oscillator, and frequency dividers. The DC voltage at RI is
limited to approximately 22 V in regulation. To protect the IC
from telephone line transients, an SCR is triggered when the
regulator current exceeds 50 mA. The SCR diverts current
from the shunt regulator and reduces the power dissipation
within the IC.
External Components
R1
Line Input
R1 affects the tone ringer input
Register
impedance. It also influences
ringing threshold voltage and
limits current from line transients.
Range: 2.0 to 10 kΩ.
C1
Line Input
C1 AC couples the tone ringer to
Capacitor
the telephone line and controls
ringer input impedance at low
frequencies.
Range: 0.4 to 2.0 µF.
R2
Oscillator Resistor Range: 150 to 300 kΩ.
C2
Oscillator
Range: 400 to 3000 pF.
Capacitor
R3
Input Current R3 controls the ringing threshold
Sense Resistor voltage. Increasing R3 decreases
the ring-start voltage.
Range: 5.0 to 18 kΩ.
C3
Ringing Threshold C3 filters the AC voltage across
Filter Capacitor R3 at the input of the ringing
threshold comparator. It also
provides dialer transient rejection.
Range: 0.5 to 5.0 µF.
C4
Ringer Supply C4 filters supply voltage for the
Capacitor
tone generating circuits. It also
provides an AC current path for
the 10 VRMS ringer signature
impedance.
(Range: 1.0 to 10 µF).
Analog Integrated Circuit Device Data
Freescale Semiconductor
34017A
7
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