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TEA1111AT/C1

Speech circuit with dialler interface,regulated supply and earpiece volume control

Philips Electronics 

Philips Semiconductors

Speech circuit with dialler interface, regulated

supply and earpiece volume control

Product specification

TEA1111A

LED control (pin LEDC)

The TEA1111A gives an on-hook/off-hook status

indication. This is achieved by a current made available at

pin LEDC to drive an external LED circuit connected

between pins SLPE and LN (see Fig.7). In the low voltage

area, which corresponds to low line current conditions, no

current is available for this LED. For line currents higher

than a threshold, the LEDC current increases

proportionally to the line current (with a ratio of 1:150).

The LEDC current is internally limited to 470 µA

(see Fig.8).

For 12 mA < Iline < 82 mA: ILEDC = -I-l-i-n--1-e---5-–--0--1----2-

This LED circuit is referenced to SLPE. Consequently, all

the LED supply current will flow through the RSLPE resistor,

and does not affect the behaviour of the AGC.

Set impedance

In the audio frequency range, the dynamic impedance is

mainly determined by the RCC resistor. The equivalent

impedance of the circuit is illustrated in Fig.9.

LN

24

2.4

Ω

kΩ

BC858B

LEDC

SLPE

FCA056

Fig.7 LED circuit configuration.

handboo5k,0h0alfpage

I LEDC

(µA)

400

FCA057

300

200

100

0

0

20

40

60

80

100

Iline (mA)

Fig.8 LEDC current versus line current.

1999 Nov 22

LN

handbook, halfpage

LEQ

RP

RCC

619 Ω

Vref

SLPE

RSLPE

20 Ω

VEE

REG

CREG

4.7 µF

VCC

CVCC

100 µF

MBE788

LEQ = CREG × RSLPE × RP.

RP = internal resistance.

RP = 17.5 kΩ.

Fig.9 Equivalent impedance between LN and VEE.

8

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