TEA1085 Philips Semiconductors, TEA1085 Datasheet - Page 8

• Manufacturer Part Number: TEA1085
• Description: Listening-in circuit for line-powered telephone sets
• Manufacturer: Philips Semiconductors

ndbook, halfpage
Philips Semiconductors
Supply amplifier stability (SDC) pin 3
To ensure stability of the TEA1085/TEA1085A, in
combination with a transmission IC of the TEA1060 family,
a 47 pF capacitor connected between SDC and SUP and
a 150 H coil connected between SUP and the positive
line terminal (Fig.16) is required.
Loudspeaker amplifier (LSI1/LSI2 and QLS1/QLS2)
pins 5/6, 21/22
The TEA1085/TEA1085A have symmetrical inputs at LSI1
and LSI2. The input signal is normally taken from the
earpiece output of the transmission circuit via a resistive
attenuator (see Fig.3). The amount of attenuation must be
chosen in accordance with the receive gain of the
transmission IC (which depends on the sensitivity of the
earpiece transducer). The maximum input signal level is
450 mV(RMS) at T
The outputs QLS1 and QLS2 can be used for single ended
drive (SE) or bridge tied load drive (BTL). The output
stages have been optimized for use with a 50
loudspeaker (e.g. Philips type AD2071).
The gain of the amplifier is fixed to 35 dB for the SE drive
and
control are left open-circuit or are connected to V
The volume control can be obtained by using a
potentiometer at the input and/or by the logic control
function.
March 1992
V BB
Listening-in circuit for line-powered
telephone sets
(V)
Fig.5
5.5
5.1
4.7
4.3
3.9
3.5
41 dB for the BTL drive (when the inputs for logic
10
Stabilized supply voltage as a function of
R38.
amb
= 25 C.
10
2
R38 (k )
MGR035
10
V BB = 3.60 V
3
SS
).
8
Logic gain control (GSC1 and GSC2) pins 7 and 8
The logic inputs GSC1 and GSC2 can be used to reduce
the gain of the loudspeaker amplifier by means of the logic
gain control function in 3 steps of 6 dB.
Table 1 Data for microcontroller drive of logic inputs
Where:
0 = connection to V
1 = applying a voltage
GSC2
0
0
1
1
GSC1
0
1
0
1
SS
or left open-circuit
TEA1085; TEA1085A
gain
(dB)
28.7
22.2
35
17
V
SS
1.5 V
Preliminary specification
gain reduction
(dB)
12.2
6.3
18
0