
2000 Mar 21
7
Philips Semiconductors
Product specication
Low voltage telephone transmission circuit with
dialler interface and regulated strong supply
TEA1114A
THE INTERNAL SUPPLY POINT (PIN VCC)
The internal circuitry of the TEA1114A is supplied from
pin VCC. This voltage supply is derived from the line
voltage by means of a resistor (RCC) and must be
decoupled by a capacitor CVCC. It may also be used to
supply some external circuits. The VCC voltage depends
on the current consumed by the IC and the peripheral
circuits as:
(see also Figs 4 and 5). Irec is the current consumed by the
output stage of the earpiece amplifier.
V
CC0
V
LN
R
CC
I
CC
×
–
=
V
CC
V
CC0
R
CC
I
P
I
rec
+
()
×
–
=
handbook, halfpage
MGK806
Irec
EXTERNAL
CIRCUITS
IP
VEE
VCC
VCC0
RCC
Fig.4
VCC used as supply voltage for external
circuits.
handbook, halfpage
0
3
2
1
0
12
4
3
MGL827
IP
(mA)
VCC (V)
(2)
(1)
1.9 mA
1.6 mA
Fig.5
Typical current IP available from VCC for
peripheral circuitry.
VCC ≥ 2.5 V; VLN = 4.35 V at Iline = 15 mA; RCC = 619 ;
RSLPE =20 .
Curve (1) is valid when the receiving amplifier is driven:
VQR(rms) = 150 mV; RL1 = 150 .
Curve (2) is valid when the receiving amplifier is not driven.
THE REGULATED SUPPLY POINT (PIN VDD)
The VDD regulator delivers a stabilized voltage for the
peripherals in transmission mode (nominal VLN) as well as
in ringer mode (VLN = 0 V). The regulator (see Fig.6)
consists of a sense input circuit, a current switch and a VDD
output stabilizer. The regulator operates as a current
source at the LN input in transmission mode; it takes a
constant current of 4.3 mA (at nominal conditions) from
pin LN. The current switch reduces the distortion on the
line at large signal swings. Output VDD follows the
DC voltage at pin LN (with typically 0.35 V difference) up
to VDD = 3.3 V. The input current of the regulator is
constant while the output (source) current is determined by
the consumption of the peripherals. The difference
between input and output current is shunted by the internal
VDD stabilizer.
In ringer mode, the stabilizer operates as a shunt stabilizer
to keep VDD at 3.3 V. In this mode, the input voltage
VLN = 0 V while the input current into pin VDD is delivered
by the ringing signal. VDD has to be decoupled by a
capacitor CVDD.