NTE1690 データシートの表示（PDF） - NTE Electronics
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NTE1690 Datasheet PDF : 4 Pages
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Pin Descriptions (Cont’d):
Adjustment of the emitter load resistor results in variation of the mean DC current during tone genera-
tion, the sine–wave signal current through the output transistor, and the output distortion. Increasing
values of load resistances decreases both the signal current and distortion.
Functional Description:
With no key inputs to the device the oscillator is inhibited, the output transistor is pulled OFF and de-
vice current consumption is reduced to a minimum. Key closures are sensed statically to ensure no
modification of the line when tones are not being generated. Any key closure activates the MUTE
output, starts the oscillator and sets the high group and low group programmable counters to the ap-
propriate divide ratio. These counters sequence two ratioed–capacitor D/A converters through a se-
ries of 28 equal duration steps per sine–wave cycle. The two tones are summed by a mixer amplifier,
with pre–emphasis applied to the high group tone. The output is an NPN emitter–follower requiring
the addition of an external load resistor to VSS. This resistor facilitates adjustment of the signal current
flowing from VDD through the output transistors.
The amplitude of the output tones is directly proportional to the device supply voltage.
Tone
Group
Low
Group
fL
High
Group
fH
Table I. Output Frequency Accuracy
Valid
Input
Standard
DTMF (Hz)
Tone Output % Deviation
Frequency from Standard
R1
697
694.8
–0.32
R2
770
770.1
+0.02
R3
852
852.4
+0.03
R4
941
940.0
–0.11
C1
1209
1206.0
–0.24
C2
1336
1331.7
–0.32
C3
1477
1486.5
+0.64
C4
16334
1639.0
+0.37
SINGLE TONE
INHIBIT
X
X
X
1
1
1
0
0
0
Table II. Functional Truth Table
TONE
DISABLE
ROW
COLUMN
Tones
Low
High
O
X
X
0V
0V
X
O/C
O/C
0V
0V
1
One
One
fL
fH
1
2 or More
One
–
fH
1
One
2 or More
fL
–
1
2 or More
2 or More
VOS
VOS
1
2 or More
One
VOS
VOS
1
One
2 or More
VOS
VOS
1
2 or More
2 or More
VOS
VOS
Note 2. X is don’t care state.
Note 3. VOS is the output offset voltage.
MUTE
0
0
1
1
1
1
1
1
1
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