TEA7092 datasheet(29/57 Pages) STMICROELECTRONICS

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Table 2

Asymmetric

Symmetric

REAR = 150

Ω

REAR = 300

Ω

REAR = 600

Ω

REAR =1k

Ω

R17

33k

Ω

68kW

68k

Ω

120k

Ω

C17

680pF

330pF

220pF

The Table 3 gives the value of VEAR(RMS)(Max.), at IL = 20mA & IL = 60mA, for different values of,

R12 (68k

Ω, 82kΩ, 110kΩ), R10 (680Ω, 1200Ω to simulate a complex impedance), REAR (150Ω, 300Ω in

asymmetric mode ; 600

Ω,1kΩ in symmetric mode) and a distortion level at 2% and 10%.

Table 3

Earphone Output Level (VRMS)

R10

R12

D (%)

150

Ω (A)

300

Ω (A)

600

Ω (S)

20mA

680

Ω

68k

Ω

0.45

0.77

1.2

1.5

0.51

0.85

1.3

1.6

82k

Ω

0.45

0.9

1.4

1.8

0.51

0.96

1.52

1.92

110k

Ω

0.46

0.98

1.91

2.4

0.51

1.1

2.56

1200

Ω

68k

Ω

0.26

0.52

0.59

0.95

0.29

0.57

0.61

0.97

82k

Ω

0.39

0.64

0.87

1.25

0.42

0.69

0.89

1.33

110k

Ω

0.46

0.89

1.32

1.65

0.5

0.95

1.37

1.8

60mA

680

Ω

68k

Ω

0.28

0.6

1.2

2.3

0.32

0.69

1.4

2.5

82k

Ω

0.28

0.6

1.25

2.3

0.32

0.69

1.42

2.5

110k

Ω

0.29

0.62

1.27

2.3

0.32

0.7

1.44

2.6

1200

Ω

68k

Ω

0.28

0.6

1.23

1.9

0.32

0.69

1.4

1.98

82k

Ω

0.28

0.6

1.25

2.15

0.32

0.69

1.33

2.3

110k

Ω

0.29

0.62

1.28

2.3

0.33

0.7

1.45

2.6

The sidetone mixer stage has a limiter to avoid acoustic signal higher than 120 dBSPL on the earphone.

Example : Electrodynamic transducer : 150

Ω / 122 dBSPL/V

- R10 = 680

Ω ;

• At IL = 20mA : VEAR(Max.) = 0.51VRMS ⇒ 116.2 dBSPL

• At IL = 60mA : VEAR(Max.) = 0.33VRMS ⇒ 112.4 dBSPL

If this acoustic limitation is too low, it is possible to modify it by :

- Decreasing the gain of the sidetone attenuation = Decrease R11a & R11b.

(R13 & R27 should also be modified).

- Increasing the gain on Pin GREC (Pin 37), to maintain the same total receiving gain

⇒ Increase R17.

II - SPEECH FEATURES (continued)

II.5 - Receive Channel (continued)

TEA7092 - TELEPHONE SET INTEGRATED CIRCUIT

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