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參數資料
| 型號： | U4090B-P |
| 英文描述： | Low power dual voltage comparators |
| 中文描述： | U4090B磷[更新9 / 03。 34頁] |
| 文件頁數： | 8/34頁 |
| 文件大?。?/td> | 622K |
| 代理商： | U4090B-P |
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8
U4090B-N
4740A–CORD–09/03
1.
In speech condition the system is supplied by the line current. If the LIDET-block
detects a line voltage above the fixed threshold (1.9 V), the internal signal VLON
is activated, thus switching off RFD and RPC and switching on all other blocks of
the chip.
At line voltages below 1.9 V, the switches remain in their quiescent state as shown
in Figure 7.
OFFSACOMP disables the group listening feature (SAI, SA, SACL, AFS) below line
currents of approximately 10 mA.
When the chip is in power-down mode (PD = high), e.g., during pulse dialing, the
internal switch QS shorts the line and all amplifiers are switched off. In this condi-
tion, LIDET, voltage regulators and IMPED CONTR are the only active blocks.
During ringing, the supply for the system is fed into V
B
via the ringing power con-
verter (RPC). The only functional amplifiers are in the speaker amplifier section
(SAI, SA, SACL).
In an answering machine, the chip is powered by an external supply via pin V
B
.
This application allows the possibility to activate all amplifiers (except the trans-
mit line interface TXA). Selecting IMPSEL = high impedance activates all
switches at the ES line.
2.
3.
4.
Acoustic Feedback
Suppression
Acoustical feedback from the loudspeaker to the handset microphone may cause insta-
bility in the system. The U4090B-N offers a very efficient feedback suppression circuit,
which uses a modified voice switch topology. Figure 7 shows the basic system
configuration.
Two attenuators (TX ATT and RX ATT) reduce the critical loop gain by introducing an
externally adjustable amount of loss either in the transmit or in the receive path. The
sliding control in block ATT CONTR determines, whether the TX or the RX signal has to
be attenuated. The overall loop gain remains constant under all operating conditions.
Selection of the active channel is made by comparison of the logarithmically com-
pressed TX- and RX- envelope curve.
The system configuration for group listening, which is realized in the U4090B-N, is illus-
trated in Figure 9. TXA and SAI represent the two attenuators, the logarithmic envelope
detectors are shown in a simplified way (operational amplifiers with two diodes).
Figure 7.
Basic Voice Switch System
Log
TX
Att
Att
contr
Log
RX
Att
Handset
microphone
Loudspeaker
Hybrid
Line
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相關代理商/技術參數 |
參數描述 |
|---|---|
| U4090B-PFNG3Y | 功能描述:電信語音調制 IC COM.CORDED - FEATURE RoHS:否 制造商:Epson Electronics America 產品: 應用:Voice Guidance product 封裝 / 箱體:PQFP-52 電源電壓-最大:3.6 V, 5.5 V 最大工作溫度: 最小工作溫度: 封裝: |
| U4090B-PFNY | 功能描述:電信語音調制 IC COM.CORDED - FEATURE RoHS:否 制造商:Epson Electronics America 產品: 應用:Voice Guidance product 封裝 / 箱體:PQFP-52 電源電壓-最大:3.6 V, 5.5 V 最大工作溫度: 最小工作溫度: 封裝: |
| U4091B | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Programmable Telephone Audio Processor |
| U4091BM | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Programmable Telephone Audio Processor |
| U4091BM-AFN | 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Programmable Telephone Audio Processor |
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