TEA7092 ST Microelectronics, Inc., TEA7092 Datasheet - Page 9

• Manufacturer Part Number: TEA7092
• Description: Telephone Analog Front End
• Manufacturer: ST Microelectronics, Inc.

LOUDSPEAKER AMPLIFIER PART (continued)
Antiacoustic Feedback (T
The antiacoustic feedback system is coupled to the microphone squelch. As soon as the level on the handset
microphone is higher than VT2, the transmit gain increases and the loudspeaker gain decreases. So the transmit
and loudspeaker gains are never simultaneously at maximum gain, which reduces larsen effect.
RING MODE
Loudspeaker Power Supply in Ring Mode (T
In ring mode, it is neccessary to convert the high voltage / low current power input to a low voltage / high
current power, output to be able to drive a 50 loudspeaker, the external switch mode power supply driven
by the TEA7092 realizes this feature.
The switch mode power supply, through external component values, fixes the impedance and the start up
threshold level.
The volume control in ring mode is the same than the one used in loudspeaking mode for the highest steps,
8 steps of 4dB, and 5 more steps of 4dB each have been added, by using the code 0111011, for the lowest
one, by this way the maximum depth in ring mode for the volume control is 48dB.
Ring Frequency
The frequencies of the ring are given by : Fring
Fi can take one of the following values : 19455Hz, 21308Hz, 23551Hz or 26321Hz, and n varies between
1 and 63. Fi and n correspond to 2 codes sent on the serial bus.
Figure 5 : Loudspeaker Gain GLS versus Voltage on Microphone
Symbol
V
V
V
V
I
I
Symbol
I
I
V
Dgls(0)
Dgls(1)
Dgls(2)
Dgls(3)
LEAK1
LEAK2
V
V
RON1
VRSU
V
V
RMC1
RMC2
RES1
RES2
OUT
LS1
LS2
RI1
RI2
Leackage Current
Input Current
Start up Current
LS Supply
Stabilized Microprocessor Supply
Ring Indicator Output
Reset Output
LS Supply
Stabilized Microprocessor Supply
Ring Indicator Output
Reset Output
LS Output Level
Antiacoustic Feedback Efficiency
Parameter
Parameter
amb
= 25°C, I
L
= 20mA, see Test 4)
V
V
V
I(VZP) = 140 A, I(VLS) = 40mA
No code sent, no signal on the
loudspeaker output
V
Gain = Gain Max.,
Codes sent :
- Group listening
- FI = 26321Hz & n = 60
- Ring start
RING
RING
RING
RING
Code 0111100
Code 0111101
Code 0111110
Code 0111111
amb
= 16V, I(VZP) = 0
= V
= 22V
= 22V, I(VZP) =250 A,
Fi
n
Test Conditions
= 25°C, R
.
Test Conditions
RSU
= 22V, I(VZP) = 20 A
LS
= 50 , see Test 5)
-21.5
-26.5
Min.
-12
-17
Min.
2.75
2.8
2.7
2.7
2.9
2.9
5
3
5
-14.5
-18.5
-22.5
Typ.
-9.5
Typ.
3.05
2.95
2.95
130
5.4
3.4
3.3
3.3
5.4
40
10
60
3
-15.5
-18.5
Max.
-12
Max.
-7
3.75
150
400
150
3.5
12
TEA7092
Unit
Unit
dB
dB
dB
dB
V
mA
V
V
V
V
V
V
V
V
PP
A
A
A
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