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參數(shù)資料
| 型號： | AS2521T |
| 廠商： | AUSTRIAMICROSYSTEMS AG |
| 元件分類： | 無繩電話/電話 |
| 英文描述： | Telephone Speech Circuit with Loudhearing and Handsfree |
| 中文描述： | TELEPHONE SPEECH CKT, PDSO28 |
| 封裝： | SOP-28 |
| 文件頁數(shù)： | 4/14頁 |
| 文件大?。?/td> | 96K |
| 代理商： | AS2521T |
Preliminary
AS2520/21/20B/21B
Rev. 5.1
Page 4
May 1999
Functional Description
The AS252x contains all the voice circuits needed in
a high feature telephone instrument, i .e.:
line adaptation (ac impedance, dc characteristics,
2/4-wire conversion, power extraction)
handset speech circuit
loudhearing with enhanced anti-Larsen
handsfree with dynamic loop gain control
switching converter
The line adaptation includes line driver, ac
impedance (return loss), 2 to 4 wire converter, dc
mask and power extraction circuit for extracting the
maximum dc power from the line to supply the whole
device and peripheral circuits.
The handset speech circuit consists of a transmit and
a receive path with mute, dual soft clipping and line
regulation (pin option). A volume control is provided
with squelch and loop gain compensation to improve
signal-to-noise ratio and to assure acoustic stability.
Loudhearing and handsfree functions are also
provided. The loudhearing function includes an anti-
Larsen circuit to prevent acoustic howling.
The handsfree circuit has a novel voice control
system which is virtually independent of any
background noise and works in a dynamic half
duplex mode as close to full duplex as the acoustic
loop gain allows.
The switching converter is used to extract the
available power from the ring signal and provides a
4V supply voltage. This allows the same loudspeaker
to be used for loudhearing/handsfree and tone
ringing.
LINE DRIVER
IMPEDANCE
SYNTESIZER
POWER
EXTRACTION
DC
CONTROL
VOICE
&
POWER
CONTROL
V
DD
TX-AGC
RX-AGC
V
DD
LE
HS
TI
LO
RO
A
GND
RTH
M2
M1
CI
LI
CS
LS
V
DD
Vss
RI
STB
A
GND
MT
MT or PD
30
L +
Z
B
AS2520/21/20B/21B
MT
V
PP
V
PP
PD
PD
LEVEL
DETECTOR
300
SS
SWITCHING
CONVERTER
CM
Vss
P
LSI
VOL
LOGIC
INTERFACE
LLC
LEVEL
DETECTOR
ST-AMP
RO-AMP
LO-AMP
MI-AMP
M3
MI-AMP
HS
M4
A
PDM
INPUT
RING
Figure 2: Block Diagramme
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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