TEA7540FP [STMICROELECTRONICS]
HANDSFREE CONTROLLER; HANDSFREE控制器
| 型号： | TEA7540FP |
| 厂家： | 
ST |
| 描述： | HANDSFREE CONTROLLER |
| 文件： | 总12页 (文件大小：134K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TEA7540
HANDSFREE CONTROLLER
NOISE/SPEECH DISCRIMINATION IN EMIS-
SION AND RECEPTION
INTEGRATED SIGNAL GAIN COMPRESSOR
IN BOTH MODES
PROGRAMMABLE ATTENUATORS IN BOTH
MODES
ADAPTED TO ACOUSTIC PARAMETERS OF
ALL CABINETS
LOW OPERATING VOLTAGE2.5V
LOW OPERATING CURRENT 2.1mA
CHIP SELECT BETWEEN HANDSFREE AND
MONITORING MODES
SO28
ORDERING NUMBERS:
TEA7540FP
DESCRIPTION
This 28 pins IC is an innovative approach to quality
handsfreetelephonesets.It results froman extensive
research onspeechsignal.
PIN CONNECTION
(top view)
GND
1
28
V+
CS
OUTE
ATTE
HYST1
HYST2
TIM
2
27
26
25
24
23
22
21
20
19
18
17
16
15
IREF
OUTR
ATTR
ATR
3
4
5
6
VOL
7
AMP SUP
AMP IN
CCR
CCE
8
CE3
9
CE2
10
11
12
13
14
CR3
CE1
CR2
MICOUT
INE
CR1
RECOUT
INR
VREF
D93TL005
July 1998
1/12
T
is advanced information on a new product now in development or undergoing evaluation. Details are subject to change without
TEA7540
BLOCK DIAGRAM
2/12
TEA7540
PIN FUNCTION
N°
1
Name
GND
CS
Function
Ground
2
Chip Select
3
OUTE
ATTE
HYST1
HYST2
TIM
Transmit Attenuator Output
Transmit Attenuator Input
Transmit Channel Hysteresis
Receive Channel Hysteresis
RC Timer
4
5
6
7
8
CCE
Time Constant of the Transmit Signal Compressor
Transmit Background Noise Memorization Output
Transmit Peak Detector Output
Transmit Rectifier Input
9
CE3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
CE2
CE1
MICOUT
INE
Transmit Signal Compressor Output
Transmit Signal Compressor Input
V+/2 - Reference Voltage
Vref
INR
Receive Signal Compressor Input
Receive Signal Compressor Output
Receive Rectifier Input
RECOUT
CR1
CR2
Receive Peak Detector Output
Receive Background Noise Memorization Output
Time Constant of the Receive Signal Compressor
Handset Preamplifier Input
CR3
CCR
AMP IN
AMP SUP
VOL
Handset Preamplifier Power Supply
Volume Control
ATR
Attenuation Value
ATTR
OUTR
Iref
Receive Attenuator Input
Receive Attenuator Output
Reference Current Source
V+
the signal coming from each end has the same
level (100mV peak), the losses in each way (for
instance losses resulting from the line length in
receiving mode) are compensated and the signal
comparison is fully symetrical. The time constant
of each signal compressor decreases 80 times
more quickly than it increases to prevent from
noise increasing between words. The compress-
ing depth is 38dB.
FUNCTIONAL DESCRIPTION
SWITCHED ATTENUATORS
Fig.A represents a block diagram of a handsfree
subset with attenuators in signal mode. To pre-
vent the system from howling, the total loop gain,
including acoustic feedback through the housing
and sidetone coupling, must be less than 0dB.
For this purpose, two switched attenuators are in-
serted in each mode (emission and reception).
The attenuation is shifted from one mode to the
other, resulting from the speech level comparison
between each way.
To prevent the circuit to switch continuously in
one way, the operation of the IC must be fully
symetrical in both ways. This involves signal com-
parison, attenuationvalue.
BACKGROUND NOISE DISCRIMINATION
An additional feature provided in TEA7540 is
background noise level discrimination in each
way. The IC stores the background sound level
with a long time constant (3 to 5 seconds depend-
ing on an external RC) and compares it with the
incoming signal in order to distinguish a useful
signal (speech) from the background noise. This
background noise memorization is also used to
compensatethe noise in each mode before signal
comparison: the noise level in each mode is sub-
GAIN COMPRESSOR
In TEA7540, two signal compressors are inserted
in each mode before the signal comparison, so
3/12
TEA7540
stracted from the incoming signal before the com-
parison. So very high noise level in one mode
cannot troublethe comparison between the useful
signals.
The result of the comparison manages the attenu-
ators in the following way:
The time constant of the switch is fixed by
the timer via an external capacitor.
- When neither party is talking both attenu-
ators are set to a medium attenuation.
Thus each mode is in idle mode. The time
constant of the switch from active mode to
idle mode must be long enough to prevent
from switching to idle mode between two
words (see fig.B). This time constant is
fixed by an external RC.
- The maximum attenuation is switched on
the mode where the speech signal is the
lowest. The maximum attenuation is fixed
by two external resistor (maximum 52dB).
Figure A
Figure B
1
Em Rec
0
1
SPEECH/NOISE
0
0dB
IDLE (A max/2)
A max dB
D93TL009A
4/12
TEA7540
TEA7540 OPERATION
put the handsfree function in standby to use the
circuit in monitoring mode with the handset micro-
phone.
TEA7540 is designed to work with all kind of mi-
crophone, including Electret.
TEA7540 is powered through an external shunt
regulator (for instance the shunt regulator of the
monitor amplifier TEA7532) or an external zener
diode.
It can work at a very low voltage (2.5V) over the
circuit and it has a low current consumption
(2.1mA).
TEA7540 also handles the handset microphone
signal (AMP IN) when the system is set to normal
conversation mode.
It’s also possible via the chip select pin (CS) to
Figure C:
Application Diagram (Example of high range telephoneset using TEA7540).
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
12
Unit
V+
Supply Voltage
V
Top
Tstg
Operating Temperature
Storage Temperature Range
-20 to 70
-65 to 125
C
°
C
°
5/12
TEA7540
ELECTRICALCHARACTERISTICS (Referto testcircuits, Tamb = 25°C;V+ = 3V;f =1KHzunless otherwise
specified).
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
Fig.
SUPPLY SECTION
V+
Supply Voltage
2.5
7.0
V
1
IC
Current Consumption
Vcs = 0
Handsfree mode
Vcs= N.C.
Monitoring mode
2.1
1.1
3.0
1.5
mA
mA
1
TRANSMIT SECTION
COMPRESSOR
Rine
CR
Compressor input impedance PIN13
7.5
10.0
16.5
41.5
25.0
200
14.5
KΩ
dB
1
Compressor Range
Maximum Gain
Minimum Gain
G1max
G1min
VO
40.5
24.0
160
42.5
26.0
240
3.0
dB
2
3
4
4
5
6
2
3
dB
Output Voltage
PIN12 compressing range
mVpp
%
Tdh
Transmit Distortion
Icce1
Icce2
Vcce1
Vcce2
Compressor dacay timecurrent Increasing gain
Compressor rise time current Decreasing gain
1.0
65
1.25
85
1.5
A
A
µ
µ
105
20
Voltage drop PIN8
cce = Vref - Vpin8
G1max
G1min
0
mV
mV
V
175
225
275
PEAK DETECTOR
Rinpd Input impedance PIN11
Ice2 Rise time current
NOISE MEMORIZATION
7.5
16
10.0
20
14.5
24
K
1
7
Ω
A
µ
V1
Max voltage drop on pin 9
33
36
10
45
mV
8
ATTENUATOR
Rina
Input impedance PIN4
7.5
14.5
K
1
9
Ω
ATE-
Attenuation=
Rpin24 = 11K
Rpin24 = 15KΩ
46
58
dB
dB
Ω
20log(Voute/Vatte)
Mode: Inactive Tx, Rx
Comp. Max Gain
ATE-active Mode: Active
Rpin24 = 11K
Rpin24 = 11K
0
1.5
23
3
dB
dB
10
11
Ω
ATE-IDLE Mode: Noise Tx, Rx Comp.
Max Gain
Ω
RECEIVE SECTION
COMPRESSOR
Rinr
CR
Input impedance
PIN15
7.5
10.0
20.5
36.5
16.0
200
14.5
K
1
Ω
Compressor Range
Maximum Gain
dB
dB
G2max
G2min
Vmicout
Rdh
35.5
15.0
160
37.5
17.0
240
3.0
2
3
4
4
5
Minimum Gain
dB
Compressor output voltage
Receive Distortion
PIN16 compressing range
Increasing gain
mVpp
%
Iccr1
Compressor decay time
current
1.0
65
1.25
1.5
µA
Iccr2
Vccr1
Vccr2
Compressor rise time current Decreasing gain
85
0
105
20
A
6
2
3
µ
Voltage drop PIN20
Vccr = Vref - Vpin20
G2max
G2min
mV
mV
175
225
275
6/12
TEA7540
ELECTRICAL CHARACTERISTICS (continued)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
Fig.
PEAK DETECTOR
Rinpd
Icr2
Input impedance
Rise time current
PIN17
7.5
16
10
20
14.5
24
K
1
7
Ω
A
µ
NOISE MEMORIZATION
V1
Max voltage drop on PIN 19
33
36
10
45
mV
8
ATTENUATOR
Rina
Input impedance
PIN25
7.5
14.5
KΩ
1
9
ATR-
Attenuation= 20lg(Voutr/Vatte) Rpin24 = 11KΩ
Mode: Inactive RX, TX
Comp. Max Gain
46
58
dB
dB
Rpin24 = 15K
Ω
ATR-active Mode: Active
Rpin24 = 11K
Rpin24 = 11K
0
1.5
23
3
dB
dB
10
11
Ω
ATR-IDLE Mode: Noise RX, TX Comp.
Max Gain
Ω
ATTENUATION CONTROL SECTION
VTIME
ITIME
VTIMR
ITIMR
Tx Mode Att.Voltage
TX Mode Att.Current
RX Mode Att.Voltage
RX Mode Att.Current
190
40
250
50
325
70
mV
12
12
13
13
14
A
µ
-325
40
-250
50
-190
70
mV
A
µ
ATRVOL Volume Control
29
32
35
dB
MICROPHONE PREAMPLIFIER
Ramp
Gmic
G2off
Imput impedance
PIN21
35
19
50
20
70
21
K
Ω
Vmic = Voute-Vamp in
Vcs open
dB
Compressor Gain
Monitoring Mode
G2 = Vrecout/Vinr
Rext between PINs 2 - 28
Rext = open
Rext = 40K
36.5
16
dB
dB
Ω
Figure 2:
Test Configuration
Figure 1:
Basic Configuration
V+ = 3V
pin 7 is forced to transmit mode
pin 11 is forced to max gain
Input signal on pin 13 VINE= 1.5mVpp
output voltage VMICOUT measured on pin 12
G1max = 20log (VMICOUT / VINE)
7/12
TEA7540
Figure 3: Test Configuration
Figure 4: Test Configuration
V+ = 3V
V+ = 3V
pin 7 is forced to transmit mode
pin 11 is forced to minimum gain
Input signal on pin 13 VINE = 1.5mVpp
output voltage VMICOUT measured on pin 12
pin 7 is forced to transmit mode
Input signal on pin 13 VINE in the compressing range (5mVpp for
example)
output voltage VMICOUT measured on pin 12
G1min = 20log (VMICOUT / VINE)
Figure 5:
Test Configuration
Figure 6: Test Configuration
V+ = 3V
V+ = 3V
pin 7 is forced to transmit mode
pin 11 is forced to maximum gain
pin 7 is forced to transmit mode
pin 11 is forced to minimum gain
8/12
TEA7540
Figure 7: Test Configuration
Figure 8: Test Configuration
V+ = 3V
V+ = 3V
pin 7 is forced to transmit mode
pin 11 is forced to minimum gain
pin 7 is forced to transmit mode
pin 11 is forced to minimum gain
Figure 9: Test Configuration
Figure 10:
Test Configuration
V+ = 3V
V+ = 3V
pin 7 is forced to receive mode
pin 11 and pin 17 are forced to maximum gain
Input signal on pin 4 VATTE = 200mVpp
pin 7 is forced to transmit mode
Input signal on pin 4 VATTE = 200mVpp
ATE = 20log(VOUTE / VATTE)
ATE2 = 20log (VOUTE / VATTE) with Rpin24 = 11KΩ
9/12
TEA7540
Figure 11: TestConfiguration
Figure 12: Test Configuration
V+ = 3V
V+ = 3V
pin 7 is forced to idle mode after that the two compressor have been
forced at maximum gain by V11 and V17
Input signal on pin 4 VATTE = 200mVpp
pin 11 is forced to 100mV to force the transmit mode
VTIM_E voltage on pin 7
ITIM_E current through the mA
Rpin24 = 11K
Ω
ATE6 = 20log(VOUTE / VATTE)
Figure 13: TestConfiguration
Figure 14: Test Configuration
V+ = 3V
V+ = 3V
pin 17 is forced to 100mV to force the receive mode
pin 7 is forced to receive mode
Input signal pin 25: VATTR = 200mVpp
Rpin23 = 9KΩ
VTIM_R voltage on pin 7
ITIM_R current through the mA
ATRVOL = 20log(VOUTR / VATTR)
10/12
TEA7540
SO28 PACKAGE MECHANICAL DATA
mm
inch
TYP.
DIM.
MIN.
TYP.
MAX.
2.65
0.3
MIN.
MAX.
0.104
0.012
0.019
0.013
A
a1
b
0.1
0.004
0.014
0.009
0.35
0.23
0.49
0.32
b1
C
c1
D
E
0.5
0.020
45 (typ.)
°
17.7
10
18.1
0.697
0.394
0.713
0.419
10.65
e
1.27
0.050
0.65
e3
F
16.51
7.4
0.4
7.6
0.291
0.016
0.299
0.050
L
1.27
S
8 (max.)
°
0016572
11/12
TEA7540
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is
granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are
subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products
are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.
The ST logo is a registered trademark of STMicroelectronics
1998 STMicroelectronics – Printed in Italy – AllRights Reserved
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12/12
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