pbl38573 ETC-unknow, pbl38573 Datasheet - Page 11

• Manufacturer Part Number: pbl38573
• Description: Speech Circuit Constant Current Feeding Systems
• Manufacturer: ETC-unknow

Power supplies DCO and V +C.
(See fig.18)
supply V +C dependent of line current with
an internal shunt regulator. This regulator
senses the line voltage V L via R 3 and line
current via R 6 in order to set the correct
V +C so the circuit can generate the required
DC characteristic for a given line resistance
R Line 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 700 A)
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
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
Figure 19. Typical standard DTMF dialling telephone application.
Care has to be taken when deci-
PBL 385 73 generates its own DC
DIALLER
CMOS
1
*
4
7
2
5
0
8
3
6
9
#
MUTE
DTMF
VDD
GND
4-8M
R18
1mA into
MIC.
200
200
R1
R2
100 F
C4
C8
C9
1 F
1 F
+
10
100
9
R17
DC-supply
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.
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
R12
1k
+
7
47 F
C7
1.2V
The circuit has further a temperature
+
AM
PBL 385 73
R16
6
+
-
5
R15
18k
R4
8
R5
22k
3
15k
15k
100nF
C3
75
R6
AT
1
2
100nF
C5
PBL 385 73
910
R7
560
R9
11k
R8
R11
6.2k
6V
12
R13
11k
11
47nF
C6
7
R10
62k
1
AR
DC0
11
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
resistor and a reservoir capaciotor is
recommended in for this output.The output
current given in the specification is 2 mA..
0-470
Hook
switch
+
910
+
4
R3
13
14
47 F
C1
noise entering the line, a series
15nF
C2
+
15V
1-10M
4.7-47
1N4007
Hook
switch
1N4007
F
PBL 385 73
1N4007
1N4007
R14
10
V
+Line
DC0
-Line
Telephone
line
11