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參數(shù)資料
| 型號： | MT8870 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | () |
| 中文描述： | （） |
| 文件頁數(shù)： | 8/23頁 |
| 文件大小： | 177K |
| 代理商： | MT8870 |
MSAN-108
Application Note
A-52
Figure 7 - Modular Approach to DTMF Receiver Systems
SOURCE OF
DTMF SIGNALS
TRANSMISSION
MEDIUM
INTERFACE
DTMF
RECEIVER
CONTROL
LOGIC
FUNCTIONAL
INTERFACE
MT8870
The design of a DTMF receiving system can
generally be broken down into three functional
blocks (Fig. 7). The first consideration is the
interface to the transmission medium. This may be
as simple as a few passive components to
adequately configure the MT8870’s input stage or as
complex as some form of demodulation, multiplexing
or analog switching system. The second functional
block is the DTMF receiver itself. This is where the
receiving system’s parameters can be optimized for
the specific signal conditions delivered from the
"
front end
"
interface. The third, and perhaps most
widely varying function, is the output control logic.
This may be as simple as a 4 to 16 line decoder,
controlling a specific function for each DTMF code,
or as complex as a full blown computer handling
system protocols and adaptively varying the tone
receiver’s parameters to adjust for changing signal
conditions.
Several
conceptually designed applications are described
subsequently but first let’s consider the design of a
typical input stage.
currently
applied
and
The input arrangement of the MT8870 provides a
differential input op amp as well as a bias source
(V
REF
) which is used to bias the inputs at mid-rail.
The output of this op amp is available to provide
feedback for gain adjustment.
A typical single ended input configuration having
unity gain is shown in Figure 8.
For balanced line applications good common mode
rejection is offered by the differential configuration
(Fig. 9). In both cases, the inputs are biased to 1/2
V
DD
by V
Ref
. Consider an input stage which will
interface to a 600
balanced line. To reject common
mode noise signals, a balanced differential amplifier
input provides the solution.
With the input configured for unity gain the MT8870
will accept maximum signal levels of +1 dBm (into
600
).
The lowest DTMF frequency that must be
detected is approximately 685Hz. Allowing 0.1dB of
Figure 8 - Single Ended Input Configuration
AV =Vo
Vi
Rf
R
S
S + 1/RC
Z(
ω
) = R
1 + (1/
ω
RC)
2
1
2
f
c
=
1
2
π
RC
V
i
R
f
(3)
(2)
(1)
(4)
GS
IN-
IN+
V
Ref
+
-
V
o
MT8870
C
R
Voltage Gain;
Input Impedance;
3dB Cutoff Frequency;
=-
相關PDF資料 |
PDF描述 |
|---|---|
| MT8880C | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CE-1 | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CC | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CE | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CN | ISO2-CMOS Integrated DTMFTransceiver |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MT8870BE | 制造商:Panasonic Industrial Company 功能描述:RECEIVER |
| MT8870D | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DC | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DC-1 | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DE | 制造商:Microsemi Corporation 功能描述: |
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