
March 1994
6
Philips Semiconductors
Product specification
Versatile telephone transmission circuit with
dialler interface
TEA1065
The DC current flowing into the set is determined by the
exchange supply voltage (V
exch
), the DC resistance of the
subscriber line (R
line
) and the DC voltage on the subscriber
set (see Fig.4).
If the line current exceeds I
CC
+
0.3 mA, required by the
circuit itself (I
CC
≈
1.14 mA), plus the current I
p
required by
the peripheral circuits connected to V
CC
then the voltage
regulator will divert the excess current via LN.
V
LN
= V
ref
+
I
SLPE
×
R9 =
V
ref
+
(I
line
I
CC
0.3
×
10
3
I
p
)
×
R9
where: V
ref
is an internally generated temperature
compensated reference voltage of 4.18 V and R9 is an
external resistor connected between SLPE and V
EE
.
The preferred value of R9 is 20
. Changing R9 will
influence the microphone gain, gain control
characteristics, sidetone and the maximum output swing
on LN. In this instance, the voltage on the line (excluding
the diode rectifier bridge; see Fig.4) is:
V
line
= V
LN
+
V
GS
+
R16
×
I
DOC
where: V
GS
is the voltage drop between the gate and
source terminal of the external line current control
transistor and I
DOC
is the current sunk by pin DOC
(I
DOC
= 0 in the voltage regulator mode and increases with
I
line
in the current regulator mode).
Under normal conditions I
SLPE
>> I
CC
+
0.3 mA
+
I
p
and
for the voltage regulator mode (I
line
<
I
knee
), the static
behaviour of the circuit is equal to a 4.18 V voltage
regulator diode with an internal resistance of R9 in series
with the V
GSon
of the external line current control
transistor. For the current regulator mode (I
line
>
I
knee
), the
static behaviour of the circuit is equal to a 4.18 V voltage
regulator diode with an internal resistance of R9 in series
with the V
GSon
of the external line current control transistor
and also in series with a DC voltage source R16
×
I
DOC
(the preferred value of R16 is 1 M
at this value the
current I
DOC
is negligible compared to I
line
).
In the audio frequency range the dynamic impedance
between LN and V
EE
is equal to R1 (see Fig.8). The
internal reference voltage V
ref
can be adjusted by means
of an external resistor R
VA
. This resistor, connected
between LN and REG, will decrease the internal reference
voltage. When R
VA
is connected between REG and SLPE
the internal reference voltage will increase.
The maximum allowed line current is given in Figs 5 and 6,
where the current is shown as a function of the required
reference voltage, ambient temperature and applied
package.
Fig.4 Supply arrangement.
handbook, full pagewidth
MBA550
SLPE
STAB
REG
VEE
Ip
LN
1
DOC
12
21
24
16
22
9
TEA1065
AC
DC
peripheral
circuits
C1
0.3 mA
ISLPE
+
0.5 mA
Rline
R16
Rexch
Vexch
Iline
Vline
R1
VCC
ICC
C3
R5
R9
IDOC