U4055B/U4055B1
Low-Voltage Electronic Speech Circuit with Dialer Interface
Description
The U4055B electronic speech circuit is a linear
integrated circuit for use in telephone and other line fed
terminal equipment. It replaces the common speech
circuit with carbon microphone, hybrid transformer,
sidetone equivalent and ear protection rectifiers. A
low-cost electrodynamic transducer is used as the
earphone. It contains all components necessary for
amplification of signals and adaption to the line.
Features
D
An electronic circuit replaces the microphone hybrid
transformer
D
Symmetrical input for dynamic or piezo microphone
D
High performance through the use of dynamic
transducers as the earphone (non-linear distortion
2 %)
D
D
D
D
DTMF interface with muting
Supply voltage for dialer
High range of line feeding current
Input resistance independent of line current and
sidetone suppression circuit.
x
D
Automatic line loss compensation
D
Built-in ear protection by earphone voltage limiter
D
Operation possible from 8 mA
U4055B1:
High level mute;
U4055B:
Low level mute
Figure 1. Block diagram and pin connection
TELEFUNKEN Semiconductors
Rev. A1, 06-May-96
1 (10)
Preliminary Information
U4055B/U4055B1
Pin Description
Pin
1, 2
Symbol
Function
H
1
and H
2
The push-pull complementary
outputs of the receive amplifier.
Dynamic transducers with a
minimum impedance of 100
W
can be directly driven by these
outputs.
GND
Ground.
ST
The output of the sidetone
cancellation signal, which
requires a balanced impedance
of 8–10 times the subscribers
line impedance to be connected
to Pin 13.
CK2
Input to the line output driver
amplifier. Transmit a.g.c. applied
to this stage.
CK1
The transmit pre-amp output
respective of the DTMF output
which is normally capacitively
coupled to Pin 5.
MIC 1, Inputs of symmetrical
MIC 2
microphone amplifier with high
common mode rejection ratio.
DTMF IN The DTMF input has an internal
resistor connected to ground. It
provides the load resistor for the
emitter of a CMOS DTMF
generator. This input is only
active when MUTE (Pin 10) is
pulled high or MUTE is pulled
low.
MUTE or The MUTE input must be pulled
MUTE at least at 1.5 V (MUTE) or at
less than 0.5 V (MUTE) to mute
the MIC Amp. and Audio Amp.
and enable DTMF IN.
Pin
11
Symbol
V+
Function
Regulated output voltage of
2.7 V for biasing a DTMF
generator activated by MUTE.
The receive amplifier input. The
receiving amplification is
regulated of an a.g.c.
Positive supply voltage input to
the device. This input should be
connected to the positive output
of the polarity guard. The current
through this pin is modulated by
the transmit signal.
An external resistor (2 W) is
required from this pin to GND to
control the dc input impedance
of the circuit. It has a nominal
value of 56
W
for low voltage
operation. Values up to 100
W
may be used to increase the
available transmit output voltage
swing at the expense of low-
voltage operation.
This internal voltage bias line
must be connected to V
L
via an
external resistor, R
B
, which
dominates the ac input imped-
ance of the circuit and should be
620
Ω
for an 600
W
input
impedance or 910
Ω
for a 900
Ω
input impedance.
The range of transmit and
receive gain variations between
short and long loops may be
adjusted by connecting a resistor
R
EX1
from this pin to Pin 3
(GND). This pin can be left open
to set a.g.c. out of action.
12
REC IN
3
4
13
V
L
14
R
DC
5
6
7, 8
15
V
I
9
16
R
AGC
10
2 (10)
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A1, 06-May-96
U4055B/U4055B1
Pin Connection
Figure 2.
Absolute Maximum Ratings
Reference point Pin 3, unless otherwise specified.
Parameters
Line current
DC line voltage, t
p
= 3 ms
Power dissipation, I
L
= 100 mA
Junction temperature
Ambient temperature range
Storage temperature range
Pin 13
Symbol
I
L
V
L
P
tot
T
j
T
amb
T
stg
Value
200
20
560
150
–28 to + 80
–55 to +150
Unit
mA
V
mW
°C
°C
°C
Thermal Resistance
Parameters
Junction ambient
Symbol
R
thJA
Value
85
Unit
K/W
TELEFUNKEN Semiconductors
Rev. A1, 06-May-96
3 (10)
Preliminary Information
U4055B/U4055B1
Electrical Characteristics
Reference point Pin 3, cable equivalent = I = 1 km,
∅
0.5 mm, R’ = 184
Ω,
C’ = 37 nF, f = 1300 Hz, 0 dBm = 775 mV
rms,
R
DC
= 56
Ω
/ 2 W, T
amb
= 25°C, unless otherwise specified.
Parameters
Line voltage
Test Conditions / Pins
I
L
= 8 mA
I
L
= 20 mA
I
L
= 30 mA
I
L
= 73 mA, see figure 4
see figure 5
Pin 7 - 8
I
L
= 30 mA
=
l = 5 km
adjustable with R
AGC
I
L
= 30 to 73 mA
≅
l
= 5
km to
0 km
I
L
= 73 mA
≅
l
= 0
km
V
MIC
= 0 V
I
L
20 mA
see figure 6
Pin 8 - 3
I
L
= 30 mA
≅
I = 5 km
R
ex1
= 0 adjustable with R
ex1
I
L
= 31 mA to 78 mA = l =
5 km to 0 km
Symbol
V
L
Min.
1.8
3.0
3.6
7.7
7
57
–7
Typ.
2.1
3.3
Max.
2.6
3.6
4.5
9.7
13
61
–9
Unit
V
V
V
V
kΩ
dB
dB
Transmit and sidetone
Input resistance
Gain
R
i
G
s
D
G
s
n
o
G
STA
R
D
G
D
D
G
D
V
0
10
59
Noise at line weighted
psophometrically
Sidetone reduction
DTMF-Amplifier
Input resistance
DTMF Gain
–70
10
8
9
–7
15
10
–68
20
13
13
–9
dBm
dB
kΩ
dB
dB
y
Volume range d 5%
Receiving amplifier
Input resistance
Gain
y
1
50
–3
–6
V
RMS
kΩ
dB
dB
see figure 4
Pin 12 - 3
R
HH
= 300
Ω,
I
L
= 30 mA
≅
l =
5 km
R
HH
= 300
Ω
adjustable with
R
AGC,
I
L
= 31 mA to 78 mA
l = 5 km to 0 km
I
L
= 78 mA = l = 0 km
S2 = 0
I
L
20 mA
I
L
20 mA
R
i
G
R
–1
–5
–5
–7
D
G
R
n
i
G
RM
V
0
I
M
V
Moff
V
M on
I
M
V
M off
V
M on
V+
Receiving noise at earphone
weighted psophometrially
Gain change when muted
Output saturation threshold
MUTE or MUTE-input
MUTE-input current
MUTE off input voltage
MUTE on input voltage
MUTE-input current
MUTE off input voltage
MUTE on input voltage
Supply voltage
Output voltage
–80
15
0.8
20
1.5
10
1.5
3
2.5
2.9
20
1
50
–71
24
1.5
80
0.3
30
0.3
dBm
dB
V
pp
µA
V
V
µA
V
V
V
V
µA
mA
y
y
Pin 9 = 0 V
Pin 9 = 1.5 V
20
Output current
see figure 4
I
L
20 mA MUTE or MUTE
switched off
switched on
Pin 10
I
L
20 mA MUTE or MUTE
switched off
switched on
Pin 10
y
6.1
3.1
30
y
I+
1
4 (10)
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A1, 06-May-96
U4055B/U4055B1
D
GRM = 20 lg VR
VR
GR = 20 lg
V
L
V
RM
Figure 3. Receiving amplifier
TELEFUNKEN Semiconductors
Rev. A1, 06-May-96
VRM : Receiving voltage when muted
G R : Receiving gain at 0 km
5 (10)
Preliminary Information
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