pbl388131sot ETC-unknow, pbl388131sot Datasheet - Page 11

• Manufacturer Part Number: pbl388131sot
• Description: Voice-switched Speakerphone Circuit With Built Loudspeaker Amplifier
• Manufacturer: ETC-unknow

the dc. set volume control on
the loudspeaker amplifier of
PBL 388 13.
wholly internal function to lower the gain at
low supply voltages. This is to avoid that
the power stage dies and causes breaks in
the output signal at long line lengths ie. low
currents in combination with high input
signals. This DC controlled volume is
externally accessible in the PBL 388 13
and can thus be utilized in several ways.
Figure 23. Loudspeaker amplifier current supply system.
Figure 24. DC - volume control options.
Some optional features using
PBL
388 13
PBL
388 13
b).
a).
Speech IC
The DC set volume control has an
V
Z
19
19
RE
R
I
= V ;
0
This resistor sets
the max. attenuation
R
2
T
1
X
R
I
B
V
+
R
V
R
+
C
= I
Weighted
resistors
This resistor sets
the min. attenuation
position on the pot.
+
I
R x
C
V c
V
Three bit
digital
signal
RE
R;
I
E
+
I
L
R
21
= I
19
18
22
17
with a DC- voltage from a potentiometer.
with a digital signal ( for ex. 8 - levels ).
volume control by connecting a resistor
from the DC - control pin 19 to the output of
the receiver detector at pin 9. Care has to
be taken not to disturb the speech switching
balance. If the resistor is made too low
ohmic the same value has to be applied on
the transmitter detector output at pin 6 as
well as that the capacitors at the detector
outputs have to be made bigger.
can be combined with the volume control.
A draw back with the fixed level is that
when setting it in to inhibit clipping distortion
at a long line ie. low level, the level will not
increase with short lines even if the supply
voltage would allow it. In the other case
when setting the level for a short line some
amplitude clipping on long line can be
expected.
the ”real” output level that means that the
"softclipping" will follow the line current
changes and will at all times give the opti-
mum distortion limiting performance.
E
R
V
a). To control the loudspeaker volume
b). To control the loudspeaker volume
c). An AGC can be combined with the
d). A ”softclipping” with a fixed level
e). A ”softclipping” that is controlled by
S
= I
+
-
= 0 then I
B
+ I
C
;
C
20
I
V
= 0
C
s
< 50 I = 50
2,6V Level shift
x
2V DC-
supply
E
I
+
-
L
PBL 388 13
x
Figure 25. DC - volume control options.
V
R
PBL
388 13
PBL
388 13
c).
R
PBL
388 13
E
d).
e).
= 50
19
19
18
9
11
20
17
19
16
23
x
10 F
R
R
+
E
+
10 F
+
x
pin 4
audio input
from Rx
channel
PBL 388 13
I
Resistor that is added
and which determines
the dynamics of the AGC
R
+ Line
- Line
Resistor that sets the
"softclipping" level
Sets the steepness
of the "softclipping"
Resistor that sets the
"softclipping" level
To volume
control
To volum
control
To volume
control
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