Philips Semiconductors
Product specification
Low voltage versatile telephone
transmission circuit with dialler interface
TEA1110A
handbook, full pagewidth
Rline
Iline
RCC
619
Ω
LN
1
from pre amp
VCC
14
IP
ICC
I
*
100
µF
CVCC
peripheral
circuits
Rexch
Ish
Vexch
Vd
TEA1110A
2
SLPE
ISLPE
RSLPE
20
Ω
3
REG
CREG
4.7
µF
MGG737
11
VEE
Fig.3 Supply configuration.
The internal circuitry of the TEA1110A is supplied from
pin V
CC
. This voltage supply is derived from the line
voltage by means of a resistor (R
CC
) and must be
decoupled by a capacitor C
VCC
. It may also be used to
supply peripheral circuits such as dialling or control
circuits. The V
CC
voltage depends on the current
consumed by the IC and the peripheral circuits as shown
by the formula:
V
CC
=
V
CC0
–
R
CCint
× (
I
P
–
I
rec
)
V
CC0
=
V
LN
–
R
CC
×
I
CC
(see also Figs 5 and 6).
R
CCint
is the internal equivalent resistance of the voltage
supply, and I
rec
is the current consumed by the output
stage of the earpiece amplifier.
The DC line current flowing into the set is determined by
the exchange supply voltage (V
exch
), the feeding bridge
resistance (R
exch
), the DC resistance of the telephone line
(R
line
) and the reference voltage (V
ref
). With line currents
below 7.5 mA, the internal reference voltage (generating
V
ref
) is automatically adjusted to a lower value. This means
that more sets can operate in parallel with DC line voltages
(excluding the polarity guard) down to an absolute
minimum voltage of 1.6 V. At currents below 7.5 mA, the
circuit has limited sending and receiving levels. This is
called the low voltage area.
MGD176
handbook, halfpage
6.0
Vref
(V)
5.0
4.0
(1)
(2)
3.0
10
4
10
5
10
6
RVA (Ω)
10
7
(1) Influence of R
VA
on V
ref
.
(2) V
ref
without influence of R
VA
.
Fig.4 Reference voltage adjustment by R
VA
.
1997 Apr 22
5
PHILIPS [ NXP SEMICONDUCTORS ]
