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PBL38570 Schematic ( PDF Datasheet ) - Ericsson

Teilenummer PBL38570
Beschreibung Universal Speech Circuit
Hersteller Ericsson
Logo Ericsson Logo 




Gesamt 12 Seiten
PBL38570 Datasheet, Funktion
September 1997
PBL 385 70
Universal Speech Circuit
Description.
Key features.
PBL 38570 is a monolithic integrated speech transmission circuit for use in electronic • Minimum number of external
telephones. It is designed to accomodate either a low impedance dynamic or an electret
components, 7 capacitors and 11
microphone. A separate input for DTMF dialling tones that is controlled by a mute signal,
resistors.
and a signal summing point at the transmitter input, are available.
• Easy adaption to various market
An internally preset line length compensation can be adjusted with external resistors
needs.
to fit into different current feed systems as for ex. 48 V, 2 x 200 ohms, 48 V, 2 x 400 ohms • Mute control input for operation with
and 48 V, 2 x 800 ohms. The line length compensation can be shut off in either high or
DTMF - generator.
low gain mode. Application dependent parameters such as line balance, side tone level, • A separate input for DTMF tones
transmitter and receiver gains and frequency responces are set independently by
controlled by mute.
external components which means an easy adaption to various market needs.
• Transmitter and receiver gain
The setting of the parameters if carried out in certain order will counteract the
regulation for automatic loop loss
interaction between the settings.
compensation.
A number of different DC - supplies are provided to feed microphones and diallers. • Extended current and voltage range
5 - 130 mA, down to 2 V.
• Differential microphone input for
good balance to ground.
• Balanced receiver output stage.
• Stabilized DC - supplies for low
current CMOS diallers and electret
microphones.
• 18 - pin DIP and 20 - pin SO packa-
ges.
• Short start up time.
• Excellent RFI performance.
DTMF
input
Mic.
Mute
(active low)
DC-output for
external devices
10
AD
12
13 AM
DC-supply
89 7
6
Sense input
1
PBL 385 70
AT AR
17
18
5 11 3
2
15 16 14 + 4
5 Gain
regulation
+
43
2
1
+
Telephone
line
1. Line impedance and radio interference suppression.
2. Transmit gain and frequency response network.
3. Receive gain and frequency response network.
4. Side tone balance network.
5. DC-supply components.
Figure 1. Functional diagram. DIP package.
20-pin plastic SO
18-pin plastic DIP
1






PBL38570 Datasheet, Funktion
PBL 385 70
DC - characteristic
The DC - characteristic that a telephone
set has to fulfill is mainly given by the
network administrator.Following para-
meters are useful to know when the DC
behaviour of the telephone is to be set:
The voltage of the feeding system.
The line feeding resistance 2x... ohms.
The maximum current from the line at
zero line length.
The min. current at which the telephone
has to work (basic function).
The lowest and highest voltage
permissible across the telephone set.
The highest voltage that the telephone
may have at different line currents is
normally set by the network owners
specification. The lowest voltage for the
telephone is normally set by the voltages
that are needed for the different parts of
the telephone to function. For ex. for trans-
mitter output amplifier, receiver output
amplifier, dialler, speech switching and
loudspeaker amplifier in a handsfree
telephone etc.
R6 will set the slope of the DC-char. and
the rest of the level is set by some constants
in the circuit as shown in the equation
below. The slope of the DC-char. will also
influence the line length regulation (when
used ) and thus the gain of both transmitter
and receiver. See the table under gain
regulation.
VLine 2 + 1. 5 R 6 Iline
Vtelephoneline 1. 5V + Vline
Microphone amplifier
The microphone amplifier in PBL38570
is divided into two stages. The first stage is
a true differential amplifier providing high
CMRR (-55 to -65 dB typical) with voltage
gain of 19 dB. This stage is followed by a
gain regulated amplifier with a regulation
range of 5 ± 2 dB. The input of the
microphone amplifier can be used for
dynamic or electret transducers.
See fig. 8.
An electret microphone with a built in
FET amplifier is to be seen from outside as
a high impedance constant current gene-
rator and is normally specified with a load
resistance of 2k. This is to be considered
as max. value and by using it will render the
max. gain from the microphone. This level
of input signal that is unnecessary high will
result in clipping in the microphone amplifier
and could in mute condition permeate
through the input to the circuits reference
V
16
14
12
10
8
6
4
2
20 40 60
Figure 7. DC-characteristics. (R6 = 75)
(a) PBL 385 70
11
12
M
13 +
Dynamic
microphone
R
C+
(c)
11
4
PBL 385 70
12
M
13 +
Balanced electret microphone.
An additional RC filterlink is
recommended if pin 4 is used
as a supply.
Figure 8. Microphone options.
6
V telephone line
V line
V pin 4
V pin 2
V pin 8 o. 9
(DC supply)
IL
80 100 120 mA
(b) 4 PBL 385 70
11
12
M
13 +
Unbalanced electret
mic. with balanced
signal, DC-supply from
pin 4.
DC
Pin 8 or 9.
(d)
11
12
PBL 385 70
M
13 +
Balanced electret
microphone

6 Page









PBL38570 pdf, datenblatt
PBL 385 70
Ordering Information
Package
Plastic DIP
Plastic SO
Plastic SO
Temp. Range
-40 to +70°C
-40 to +70°C
-40 to +70°C
Part No.
PBL 385 70/1N
PBL 385 70/1SO
PBL 385 70/1SO:T
Information given in this data sheet is believed to be
accurate and reliable. However no responsibility is
assumed for the consequences of its use nor for any
infringement of patents or other rights of third parties
which may result from its use. No license is granted
by implication or otherwise under any patent or patent
rights of Ericsson Components. These products are
sold only according to Ericsson Components' general
conditions of sale, unless otherwise confirmed in
writing.
Specifications subject to change without
notice.
1522-PBL 385 70/1
© Ericsson Components AB
September 1997
Ericsson Components AB
S-164 81 Kista-Stockholm, Sweden
Telephone: +46 8 757 50 00
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