TEA1064A/C1 Philips Semiconductors (Acquired by NXP), TEA1064A/C1 Datasheet - Page 15

• Manufacturer Part Number: TEA1064A/C1
• Description: TEA1064A; Low Voltage Versatile Telephone Transmission Circuit With Dialler Interface And Transmit Level Dynamic Limiting
• Manufacturer: Philips Semiconductors (Acquired by NXP)

Philips Semiconductors
R2, R3, R8, R9 and Z
compensation is obtained when the following conditions
are fulfilled:
If fixed values are chosen for R1, R2, R3 and R9, then
condition a) is always fulfilled provided
To obtain optimum sidetone suppression, condition b) has
to be fulfilled, resulting in:
where k is a scale factor; k = (R8/R1).
The scale factor k (value of R8) is chosen to meet the
following criteria:
In practice Z
line type. Therefore the value chosen for Z
an average line length giving satisfactory sidetone
suppression with short and long lines. The suppression
also depends on the accuracy of the match between
Z
March 1994
bal
compatibility with a standard capacitor from the E6 or
E12 range for Z
correct anti-sidetone bridge operation;
Low voltage versatile telephone transmission circuit
with dialler interface and transmit level dynamic limiting
Z
Z
and the impedance of the average line.
bal
bal
a) R9
b) (Z
Z
bal
//R8 << R3 to fulfil condition a) and thus ensure
R8 >> R9 to avoid influencing the transmit gain.
= (R8/R1)
bal
/[Z
line
R2 = R1
bal
varies considerably with the line length and
bal
R8]) = (Z
;
bal
Z
line
(R3
(see Fig.18). Maximum
= k
line
[R8//Z
/[Z
Z
line
line
bal
])
R1])
R8//Z
bal
should be for
bal
<< R3.
15
Example
The line impedance for which optimum suppression is to
be obtained can be represented by
210
0.5 mm diameter copper twisted-pair cable matched with
600
With k = 0.64 this results in: R8 = 390 ;
Z
The anti-sidetone network for the TEA1060 family shown
in Fig.18 attenuates the signal received from the line by
32 dB before it enters the receiving amplifier. The
attenuation is almost constant over the whole
audio-frequency range.
Alternatively a conventional Wheatstone bridge can be
used as an anti-sidetone circuit (Fig.19). Both bridge types
can be used with either resistive or complex set
impedances. (More information on the balancing of
anti-sidetone bridges can be obtained in our publication
“Versatile speech transmission ICs for electronic
telephone sets” , order number 9398 341 10011).
Notes
1. The reference used for the MUTE, DTMF and PD
2. A LOW level for any of these pins is defined by
bal
inputs is SLPE.
connection to SLPE, a HIGH level is defined as a
voltage greater than V
V
= 130
CC1
(176 /km; 38 nF/km).
(1265
0.4 V.
(820
// 140 nF). This represents a 5 km line of
// 220 nF).
SLPE
1.5 V and smaller than
Product specification
TEA1064A