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參數(shù)資料
| 型號： | NT95089 |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | Tone Dialer |
| 中文描述： | 撥號音 |
| 文件頁數(shù)： | 6/11頁 |
| 文件大?。?/td> | 309K |
| 代理商： | NT95089 |
NT95089
6
Pin Descriptions (continued)
Pin No.
Designation
Description
16
TONE
DTMF signal output
The NT95089 uses a Johnson counter and resistor ladder network (see
block diagram) to synthesize the two desired frequencies in sinewaves.
The ladder network is then used to mix the two. The NT95089 uses a
bipolar NPN transistor, connected as emitter follower, to allow proper
impedance transformation and at the same time preserve signal level
Functional Description
Crystal Specification
Standard TV color burst crystals have a much tighter
tolerance specification than is necessary for tone
generation applications. Because the required tolerance
specification for this type of application is more relaxed,
lower-cost crystals can be used. Crystals with the
following specifications are suggested for use with the
NT95089:
Frequency: 3.58MHz
±
0.02%.
R
S
≤
100
, L
M
= 96 mH, C
M
= 0.02pF, C
H
= 5pF, C
L
=
12pF.
AKD
Output Structure
N-CHANNEL OPEN DRAIN OUTPUT
DTMF Generator
The NT95089 has a well designed, digitally-synthesized
sinewave with an 8-level, 16-segment structure. (See
Figure 2.)
Reference Voltage
The structure of the reference voltage employed in the
NT95089 is shown in Figure 3. It has the following
characteristics:
a) V is proportional to the supply voltage. Output tone
amplitude, which is a function of (VDD - V
REF
),
increases with supply voltage. (Figure 4).
b) The temperature coefficient of V
REF
is low due to a
single V
BE
drop. Use of a resistor divider also
contributes to providing an accuracy of better than
10%. As a result, tone amplitude variations over
temperature and unit to unit differences are held to
less than
±
1.0dB.
c) Resistor values in the divider network are chosen so
that V
REF
is above the V
BE
drop of the tone output
transistor even at the low end of the supply voltage
range. This eliminates tone output clipping at low
supply voltage and improves distortion performance.
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