TEA7063 datasheet(10/15 Pages) STMICROELECTRONICS

10 / 15 page

6. CURRENT SOURCE FOR SPEAKERPHONE

6.1 Current Source (pin 12)

Most of the DC current available from the line is

delivered by the speech circuit at the output Isource

(pin 12) through an internal current generator.

Typical values of this current, lLS with R9 = 100K,

are:

ILS = (0.3

• ILINE)

for ILINE < 16.5mA

ILS = (0.9

• ILINE -10mA) for ILINE > 16.5mA

(ex: ILINE = 16mA then ILS = 5mA

ILINE = 30mA then ILS = 17mA

ILINE = 60mA then ILS = 44mA).

The voltage level at pin 12 must be defined by an

external regulator (i.e.: zener) and, if necessary,

filtered with a capacitor (47 to 220

µF).

In case VLINE (at pin 16) approaches voltage at

pin 12, then the internal current source switches

off and its DC current is shunt to ground through

and internal

complementary generator, thus

avoiding any negative effect on the AC and DC

impedances of the telephone set application.

5. MICROPROCESSOR INTERFACE

5.1 Microprocessor Supply (pin 19)

At ”off-hook” the first priority of the circuit is to

make some current available at the Microproces-

sor Supply (pin 19) to charge quickly the external

capacitor C2.

This charging current is Icpm = 0.6

• ILINE

T-charge of about 10ms is necessary, with C2 =

47/

µF. to charge pin 19 at the specified value of

3.3V typical at ILINE = 25mA:

T-charge =

3.3V

• C2

0.6

• ILINE

typically

Vmp = 3.3V in normal operation and current in-

creases linearly from 0.5mA min, at ILINE = 6mA,

to1.5mA, at ILINE = 25mA, remaining stable for

higher values of ILINE. (with R9 = 100K)

In general:

Imp =

130Volt

+ 0.3mA at IL > 25mA

Imp =

11Volt

+ 0.3mA at IL > 6mA

A zener of 3.9V typical is generally suggested to

Figure 8

Figure 9

TEA7063

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