- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄383641 > MT8870 (Mitel Networks Corporation) () PDF資料下載
參數(shù)資料
| 型號(hào)： | MT8870 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | () |
| 中文描述： | （） |
| 文件頁數(shù)： | 6/23頁 |
| 文件大?。?/td> | 177K |
| 代理商： | MT8870 |
MSAN-108
Application Note
A-50
Figure 5 - MT8870 Steering And GuardTime Circuit Operation
If the same valid tone-pair does not reappear before
t
GTA
then the voltage at St/GT falls below V
TSt
which
resets the timing circuit via Q
2
and prepares the
device to receive another signal. If the same valid
tone-pair reappears before t
GTA
, ESt is raised turning
on Q
1
and discharging C which resets t
GTA
. In this
case StD remains high and the tone dropout is
disregarded as noise.
Valid tone present
indication from
DIGITAL DETECT
circuit.
To OUTPUT
LATCHES
COMP.
+
-
MT8870
V
TSt
V
SS
n
Q
2
V
DD
St/GT
ESt
(18)
(17)
(16)
StD (15)
V
DD
C
R
A logical HIGH indicates that a
valid signal is being receved.
p
Q
1
DELAY
STEERING TRUTH TABLE
0
0
1
1
<V
TSt
>V
TSt
<V
TSt
>V
TSt
0
Z
Z
1
0
1
0
1
ESt
St(/GT)
(St/)GT
StD
0 - LOGIC LOW
1 = LOGIC HIGH
Z = HIH IMPEDANCE
V
TSt
= Threshold Voltqae
(typically 1/2 V
DD
)
Simplified steering circuit. Initially ESt is low, C is fully charged applying 0V to St/GT and Q
2
is on. Upon reception of a valid tone
pair ESt is raised turning off Q
2
and allowing C to discharge through R which increases the voltae at St/GT. When VTSt is reached
the comparator output goes high indicating a valid signal, latches the outputs and turns on Q
which discharges C. When the tone
pair is lost ESt goes low Q
turns off and C charges through R decreasing the voltage at St/GT. When V
TSt
is reached StD goes low
and Q
2
turns on resetting the timing circuit.
Steering circuit truth table. Note that pin 17 (St/GT) acts as both an input and an output depending on the relative states of ESt
and the comparator output.
To provide good reliability in a typical telephony
environment, a DTMF receiver should be designed to
recognize a valid tone-pair greater than 40mS in
duration and, to accept as successive digits, tone-
pairs that are greater than 40mS apart. However in
other environments, such as two-way radio, the
optimum tone duration and intra-digit times may
differ due to noise considerations.
By adding an extra resistor and steering diode (Fig.
6b, 6c) t
GTP
and t
GTA
can be set to different values.
Guard time adjustment allows tailoring of noise
immunity and talk-off performance to meet specific
system needs.
Talk-off is a measure of errors that occur when the
receiver falsely detects a tone pair due to speech or
background noise simulating a DTMF signal.
Increasing t
GTP
improves talk off performance since
相關(guān)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(guān)代理商/技術(shù)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: |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。