|
|
PDF PBL38573 Data sheet ( Hoja de datos )
| Número de pieza | PBL38573 | |
| Descripción | Speech Circuit for constant current feeding systems | |
| Fabricantes | Ericsson | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de PBL38573 (archivo pdf) en la parte inferior de esta página. Total 15 Páginas | ||
|
No Preview Available !
PBJLun3e81597993
PBL 385 73
Speech Circuit for constant current
feeding systems
Description.
Key features.
PBL 38573 is a monolithic integrated speech transmission circuit for use in
electronic telephones. It is intended specially for telephone lines with constant current
feed. Maximum line current less than 130 mA in DIL package (100 mA in SO package).
It is designed to accomodate either a low impedance dynamic or an electret microphone.
A signal summing point at the transmitter input is available for DTMF dialler- and
possible monitor or handsfree signals. An available internally preset line length
compensation can be adjusted or shut off in low gain mode with external resistors.
Application dependent parameters such as line balance, side tone level, transmitter and
receiver gains and frequency responces are set independently by external components
which means an easy adaption to various market needs. The setting of the parameters
if carried out in certain order will counteract the interaction between the settings. A DC-
supply is provided to feed microphones and diallers.
1
9 PBL 385 73
MIC.
AM
10
AT
Mute
(active low)
DTMF - input
DC supply for
external devices
DC-supply
7
6
5
+
5 83
2
2
4
13
AR
12 11
14
+4
REC
3
+
1
Telephone
line
• Minimum number of external
components for function,with one filte-
red DC-supply. 6 capacitors and 10
resistors.
• Easy adaption to various market
needs.
• Mute control input for operation with
DTMF - generator.
• Transmitter and receiver gain
regulation for automatic loop loss
compensation. Disconnectable.
• Extended current and voltage range
5 - 130mA (DIP), down to 2 V.
• Differential microphone input for good
balance to ground.
• Balanced receiver output stage.
• Stabilized DC - supply for low current
CMOS diallers and electret
microphones.
• Short start up time.
• Excellent RFI performance.
• In 14- pin DIP and SO packages.
14-pin plastic SO
1. Impedance to the line and radio interference suppression
2. Transmitter gain and frequency responce network
3. Receiver gain and frequency responce network
4. Sidetone balance network
5. DC supply components
Figure 1. Functional diagram.
14-pin plastic DIP
1
1 page  
PBL 385 73
Functional description
Design procedure; ref. to fig.4.
+Line
The design is made easier through that all
settable parameters are returned to gro-
und (-line), this feature differs it from bridge
type solutions.To set the parameters in the
following order will result in that the
interaction between the same is minimized.
1. Set the circuit impedance to the line,
either resistive (600Ω) or complex. (R3
and C1). C1 should be big enough to give
low impedance compared with R3 in the
telephone speech frequency band.Too
large C1 will make the start-up slow. See
fig. 6.
2. Set the DC-characteristic that is
required in the PTT specification or in case
of a system telephone,in the PBX
specification (R6).There are also internal
circuit dependent requirements like supply
voltages etc.
3. Set the attac point where the line
length regulation is supposed to cut in
(R15 and R16). Note that in some countries
the line length regulation is not allowed. In
most cases the end result is better and
more readily achieved by using the line
length regulation (line loss compensation)
than without. See fig. 13.
4. Set the transmitter gain and
frequency response.
5. Set the receiver gain and frequency
response. See text how to limit the max.
swing to the earphone.
6. Adjust the side tone balancing
network.
7. Set the RFI suppression
components in case necessary. In two
piece telephones the often ”helically”
wound cord acts as an aerial. The
microphone input with its high gain is
especially sensitive.
8. Circuit protection. Apart from any
other protection devices used in the de-
sign a good practice is to connect a 15V
1W zener diode across the circuit , from
pin 1 to -Line.
PBL 38 573
1
4
3
C2
2
R6
Figure 6. AC-impedance.
Impedance to the line
The AC- impedance to the line is
set by R3, C1 and C2. Fig.4. The circuits
relatively high parallel impedance will not
influence it to any noticeable extent. At low
frequencies the influence of C1 can not be
neglected. Series resistance of C1 that is
dependent on the temperature and the
quality of the component will cause some
of the line signal to enter pin 4. This
generates a closed loop in the transmitter
amplifier that in it´s turn will create an
active impedance thus lowering the
impedance to the line. The impedance at
high frequencies is set by C2 that also
acts as a RFI suppressor.
In many specifications the
impedance towards the line is specified as
a complex network. See fig. 6. In case a).
the error signal entering pin 4 is set by the
ratio ≈Rs/R3 (910Ω), where in case b). the
ratio at high frequencies will be Rs/220Ω
because the 820Ω resistor is bypassed by
+ Line
1
+
AM 2 AT
Transmitter summing
input
Mute
Figure 7. Block connections.
4
3
AR
- Line
a) b)
R3
c)
220Ω
Cx
820Ω
Rs
≈1Ω
+
C1
Example:
How to connect a
complex network.
220Ω+820Ω//Cx
-Line
a capacitor. To help up this situation the
complex network capacitor is connected
directly to ground, case c). making the ratio
Rs/220Ω+820Ω and thus lessening the
error signal. Conclusion: Connect like in
case c) when complex impedance is
specified.
DC - characteristic
The DC - characteristic that a
telephone set has to fulfill is mainly given
by the network administrator. Following
parameters 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 2 x.......
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. 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
transmitter output amplifier, recei-
ver output amplifier, dialler, speech
switching.
5
5 Page 
PBL 385 73
Power supplies DCO and V+C.
(See fig.18)
PBL 385 73 generates its own DC
supply V+C dependent of line current with
an internal shunt regulator. This regulator
senses the line voltage VL via R3 and line
current via R6 in order to set the correct
V+C so the circuit can generate the required
DC characteristic for a given line resistance
RLine and the line feeding data of the
exchange. A decoupling capacitor is
needed between pins +C and -L. The V+C
supply changes its voltage linearly with the
line current. It can be used to feed an
electret microphone. Caution must be ta-
ken though not to drain too much current
out of this output because it will affect the
internal quick start circuit by locking itself
into active state. (max. permissible current
drain 700µA)
Care has to be taken when deci-
ding the resistance value of R3. See fig.6.
All resistances that are applied from +Line
to ground (-Line) will be in parallel, forming
the real impedance towards the line. This
will sometimes result in, that the ohmic
value of R3 is increased in order to comply
to the impedance specification towards the
line. The speech circuit sinks ≈ 1mA into
pin 4, which means that the working voltage
for the speech function V+ will decrease
with increasing R3, thus starving in the end
the circuit of its working voltage . This
dependency is often falsely taken as a sign
PBL 385 73
1.2V
+
-
15k
15k
Hook
switch
1
+Line
7 0-470Ω
DC0
6V
11
1-10M
+ 4.7-47
µF
VDC0
-Line
Figure 18. DC - supply for external load.
of that the circuit does not work down to the
low line current specified, but in fact it is the
working voltage at pin 4 that has become
too low. It is obvious that this problem is
also connected into what kind of DC-
characteristic is set. See fig. 8.
The circuit has further a temperature
and line current compensated DC supply
DC0 . DC0 is a voltage supply for supplying
diallers, can be used for memory back up
because it does not leak any current back
into the circuit. Typical voltage 2.4V down
to line voltage of 4.1V, in case the line
voltage is lower than 4.1V calculate ; actual
line voltage minus 1.9V. In order to pre-
vent noise entering the line, a series
resistor and a reservoir capaciotor is
recommended in for this output.The output
current given in the specification is 2 mA..
VDD
CMOS
DIALLER
MUTE
DTMF
GND
123
45 6
789
*0 #
R18
4-8M
1
R1
200Ω
MIC.
R2
200Ω
C8
1µF 9
1µF 10
C9
AM
+
DC-supply
7
65
8
PBL 385 73
AT AR
32
12 11
R17
100Ω
+ C7
47µF
R16
C4
100µF
+
R12
1k
R4
18k
R15
R5
22k
C3
100nF
R7
910Ω
R6
75Ω
C5
100nF
R11
6.2k
R8
560Ω
R9
11k
C6
47nF
R10
62k
R13
11k
13
14
+4
R3
910Ω
+ C1
47µF
Hook
switch
1N4007
1N4007
15V
C2
15nF
1N4007
1N4007
Telephone
line
R14
10Ω
Figure 19. Typical standard DTMF dialling telephone application.
11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet PBL38573.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| PBL38570 | Universal Speech Circuit | Ericsson |
| PBL385701N | Universal Speech Circuit | Ericsson |
| PBL385701SO | Universal Speech Circuit | Ericsson |
| PBL385701SOT | Universal Speech Circuit | Ericsson |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |