- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄379309 > MC33215FB (MOTOROLA INC) Telephone Line Interface and Speakerphone Circuit PDF資料下載
參數(shù)資料
| 型號： | MC33215FB |
| 廠商： | MOTOROLA INC |
| 元件分類： | 無繩電話/電話 |
| 英文描述： | Telephone Line Interface and Speakerphone Circuit |
| 中文描述： | TELEPHONE SPEECH CKT, PQFP52 |
| 封裝： | PLASTIC, TQFP-52 |
| 文件頁數(shù)： | 15/20頁 |
| 文件大?。?/td> | 456K |
| 代理商： | MC33215FB |
MC33215
15
MOTOROLA ANALOG IC DEVICE DATA
A
SWD
= Switching depth as performed in the
attenuators
To avoid howling, the maximum possible loop gain should
be below 0 dB and preferably below –10 dB for comfort. In a
practical telephone design, both the A
BMRX(max)
and the
A
RXBM(max)
will be less than 20 dB thus a switching depth of
50 dB will give a loop gain of less than –10 dB. An optimized
sidetone network is of high importance for handsfree
operation. The better the network matches with the
telephone line the less local feedback and the smaller the
switching range can be.
The amount of gain reduction A
SWD
obtained by the
duplex controller is set via resistor R
SWD
according:
ASWD
20log
3.6 x RSWD
RREF
2
(dB)
In the typical application the gain reduction will be 50 dB.
To compare the transmit and receive signals with each
other, they have to be monitored. This is done by making a
signal envelope and a background noise envelope via the
C
TSE
, C
TBN
capacitors for the transmit channel and via the
C
RSE
, C
RBN
capacitors for the receive channel. In Figure 14,
a schematic behavior of the envelopes is depicted which is
equal for both transmit and receive.
The voltage signal at the input is first transferred to a
current via the sensitivity adjust network. Then this current is
led through a diode which gives a logarithmic compression in
voltage. It is this voltage from which the signal envelope is
created by means of asymmetric charge and discharge of the
signal envelope capacitor. The noise envelope voltage then
follows in a similar way. Based on the envelope levels, the
MC33215 will switch to transmit, receive or idle mode
following Table 3. The fact that in receive mode the signal on
the base microphone is greater than it is in case of transmit
mode, due to the coupling of the high loudspeaker signal, is
automatically taken into account.
In the table, two particulars can be found. At first, the set
will go to idle mode if the signals are not at least 4.5 dB
greater then the noise floor, which calculates as a 13 mV
voltage difference in envelopes. This avoids continuous
switching over between the modes under slight variations of
the background noise due to, for instance, typing on a
keyboard. Second, a dial tone detector threshold is
implemented to avoid that the set goes to idle mode in
presence of a continuous strong receive signal like a dial
tone. The dial tone detector threshold is proportional to the
R
RSA
resistor. In the typical application with R
RSA
= 3.3 k
,
the threshold is at 1.26 mVrms at the input RXI or 20 mVrms
at the line. Line length AGC is of influence on the dial tone
detector threshold, increasing the level depending on the line
current with a maximum of 6.0 dB.
In order to perform a correct comparison between the
signal strengths, the sensitivity of the envelope detectors can
be adjusted via the resistors connected to TSA and RSA.
Based on the above, and on the fact that there is an effective
gain of 20 dB in the transmit monitor, it can be derived that for
stable operation the following two relations are valid:
20log RTSA
20log RRSA
– ABMRX(max)
20 (dB)
20log RTSA
20log RRSA
– ASW
– ARXBM(max)
20 (dB)
By measuring the gains and choosing the R
RSA
, the limits
for R
TSA
follow. The choice for the sensitivity resistors is not
completely free. The logarithmic compressors and the
amplifier stages have a certain range of operation and, on the
receive side, the choice for R
RSA
is given by the desired dial
tone detector threshold. Figure 15 indicates the available
dynamic range for the selected value of the sensitivity
resistors.
Figure 14. Signal and Noise Envelopes
Microphone
Input Signal
1.8 V
Internal
TSA
R
TSA
C
TSA
TSE
C
TSE
C
TBN
TBN
VHF
VHF
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MC33219ADW | VOICE SWITCHED SPEAKERPHONE CIRCUIT |
| MC33219AP | VOICE SWITCHED SPEAKERPHONE CIRCUIT |
| MC33290D | ISO SERIAL LINK INTERFACE |
| MC33290 | ISO SERIAL LINK INTERFACE |
| MC33290DR2 | ISO SERIAL LINK INTERFACE |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MC33218AP | 制造商:Rochester Electronics LLC 功能描述: 制造商:Motorola Inc 功能描述: 制造商:MOTOROLA 功能描述: |
| MC33232D | 功能描述:功率因數(shù)校正 IC Critical Mode PFC RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| MC33232DG | 功能描述:功率因數(shù)校正 IC Critical Mode PFC RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| MC33232DR2 | 功能描述:功率因數(shù)校正 IC Critical Mode PFC RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| MC33232DR2G | 功能描述:功率因數(shù)校正 IC Critical Mode PFC RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。