TEA7088AFP datasheet(5/17 Pages) STMICROELECTRONICS

5 / 17 page

ELECTRICAL SPECIFICATIONS (continued)

AC Characteristics (Tamb =25

°C; RL = 600Ω ; Logic in Default Mode unless otherwise noted)

Symbol

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

Return Loss

Test 2, IL = 22mA

f = 300/3400Hz, VAC = -10dBV

Transmit Characteristics

(Tamb =25

°C; RL = 600Ω ; f = 1kHz ; Logic in Default Mode unless otherwise noted)

Symbol

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

Gtx

Gtxl

Gtxs

Microphone Gain

Test 3, Vm = -55dBV

R8 = 1.3k

Ω, R25 = 3.9kΩ

IL = 22mA

IL = 90mA

Zmic

Microphone Input Impedance

between MIC1 & MIC2

Ω

Ntx

Noise

Test 3, 2k

Ω on microphone inputs,

IL = 22mA

-76

dBmp

Mmic

Microphone Mute

Test 3, Vm = -55dBV, IL = 22mA

Dtx

VL Max.

Soft Clipping

- Distortion

- Maximum Level on Line

Test 3, IL = 22mA, see Figure 2

Vm = -41dBV

Vm = -34dBV

1.5

The maximum gain Gtl is adjustable between 44

and 56dB with R8 :

Gtxl

= 20log







820

⋅

R10 // RL

+ R11

R8 // 50k

Ω







The AGC variation is programmed with one resistor

connected on Pin AGC. ISL is the line current at

which the gain must be decreased by 6dB.

R25

(Ω) =

300

ISL

− 5mA

(R25 > 2.6k

Ω)

For line current lower than ILL or higher than ISL,

The transmit and receive gains have a constant

value.

If no resistor or a resistor higher than 300k

Ω is

connected on Pin AGC, the gain is constant and

equal to Gtxl and Grxl.

±0.5dB.

AGC can be inhibited also through MCU code

”010100”. In this case Tx and Rx gains are fixed

2dB lower than the maximum gain.

The minimum saturation voltage of the TEA7088A

respect to ground is 2.2V. On long line, when the

voltage over TEA7088A is low, the softclipping

function automatically limits the AC dynamic to

avoid to reach the 2.2V limit on TEA7088A respect

to ground.

0.1

100

0.1

Thre s hold

Leve l

microph on e peak ( m V)

-2

-5

-10

-15

Figure 2 : Softclipping

4 06 08 0

10 0

AC p eak

L (mA)

AC p eak

Figure 3

TEA7088A

5/17

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