PBL 3853
Universal Speech Circuit
Description
The PBL 3853 is a biopolar integrated speech circuit with specific parameters making
it highly suitable to be used as a line interface and speech circuit in a telephone line
powered electronic payphone. Emphasis has been put on low current consumption in
the IC thus facilitating that a greater part of the available line current can be used to
power other electrical functions in the design. From a minimum line current of
16 mA, 12 mA at 4.5 V can be used to power auxiliary functions. The circuit can
optionally create an active impedance towards the telephone line, set by external
passive components, to reduce the current consumption for the transmitted signal.
The circuit is designed to be used with a low impedance dynamic microphone but can
be used with an electret type as well. The receiver drives a low ohm dynamic
transducer directly. External clamping diodes are required on the receiver output.
Both transmitter and receiver can be muted separately (receiver cut off). Line length
regulation of the gain is possible in both receiver and transmitter. It is also possible to
use the circuit without regulation. Payphone tones and confidence tone in the recei-
ver at DTMF dialling can be injected directly into the receiver amplifier where their
levels are not affected by line length regulation and without the signal going out on
the line. All pin numbers refer to DIP package unless otherwise noted.
Figure 1. Block diagram. Pin numbers in all figures refer to DIP package.
Key Features
Low own current consumption
Can operate both with active and
passive impedance towards the line
Derives a high current from the line
for auxiliary functions, 12 mA at
16 mA line current
Separate mute inputs for transmitter
and receiver (receiver cut off)
Line length regulation possible (line
loss compensation
Comes in 18 pin DIP and 20-pin SO
package
High line current operation, max.
130 mA
Especially suitable for payphone
applications
DTMF - confidence tone input
Excellent RFI performance
18-pin plastic DIP
20-pin plastic SO
PBL 3853
-
-
12
13
6
14
11
3
2
17
15
4
10
5
16
18
8
9
1
7
MA
Rx
Tx
+V
+
+
-
+
PBL3853
PBL3853
May 1996
PBL 3853
2
Figure 2. Test set up without rectifier
bridge.
Figure 3. Test set up with rectifier bridge.
R1 = 2.7 k
C1 = 150 nF
R2 = 22
C2 = 10 nF
R3 = 6.8 k
C3 = 47
F
R4 = 1.8 k
C4 = 220 nF
R5 = 75
C5 = 150 nF
R6 = 910
C6 = 47 nF
R7 = 6.2k
C7 = 100 nF
R8 = 560
C8 = 68 nF
R9 = 11 k
C9 = 4.7
F
R10 = 4.7k
C10 = 22
F
R11 = 120k
R12 = 56
D1 = Z 4.5 V
R13 = 68
D2 = 1N4148
R
C
= 30 k*
D3 = 1N4148
R
D
= 11k*
T1 = BC178B
T2 = BC178B
* values for the test set up only
Figure 4. Reference figure with line length regulation. DIP-package.
1
V
DC
IL
R 13
R12
R1
C1
R2
10
4
Mic
12
13
6
R
A
R
B
C3
+
R
C
R
D
DTMF
In
R
DTMF
R4
R3
C4
C5
R5
R6
R8
R9
Tone in
Cut-off
R7
C6
C7
R11
R10
C8
C2
-Line
D1
C10
D2 D3
C9
Rec
+
T1
+ Line
T2
5
PBL3853
AC-DC char. adjust
Transmitter mute
+ V
M
14
11
2
3
17
T
X
15
Receiver
R
x
16
8
18
7
9
-
-
-
+
+
+
+
R -0-4k
L
0 ohm when artificial
line is used
5H+5H
R = 400
+400
feed
+
E= 50V
1
2
600
V
L
I
DC
V
DC
L
I
+ LINE
MIC
REC
-
LINE
Recelver
cut-off
Transmitter
mute
Recevler
tone
input
PBL 3853
see fig 4
V
4
Z
Rec
=350
V
5
Z= 500
V
3
Z =150
Mic
V
V
+
C
C = 1
F when artificial line is used
470
F when not used
ARTIFICIAL
LINE
R -0-4k
L
0 ohm when artificial
line is used
5H+5H
U = 15-16V
z
R = 400
+400
feed
+
E= 50V
1
2
1
F
600
V
L
I
DC
V
DC
L
I
+ LINE
MIC
REC
-
LINE
Recelver
cut-off
Transmitter
mute
Recevler
tone
input
PBL 3853
see fig 4
V
4
Z
Rec
350
V
5
Z= 500
V
3
Z =150
Mic
V
V
PBL 3853
3
Absolute Maximum Ratings
Parameter
Symbol
Conditions
Min.
Max.
Unit
Line voltage
V
L
22
V
Continous operating line current, T
amb
=70
C
I
L
Dual In Line package
130
mA
Continous operating line current, T
amb
=70
C
I
L
Small Outline package
100
mA
Input voltage, all inputs
V
pinx
-0.5
Vpin4+0.5
V
Operation temperature
T
amb
-20
+70
C
Storage temperature
T
sto
-55
+125
C
Electrical Characteristics
T
amb
=+25
C. No cable and or line rectifier unless otherwise specified.
Parameter
Symbol
fig.
Conditions
Min.
Typ.
Max.
Unit
Terminal voltage
2
I
L
= 20 mA
6
V
Transmitter gain
2
20
10
log (V
2
/ V
3
),1 kHz
I
L
= 57 mA
41.6
43.0
44.4
dB
R
L
= 0
41.0
43.0
45.0
dB
R
L
= 900
- 2.2 k
46.0
48.0
50.0
dB
I
L
= 20 mA
47.0
48.0
49.0
dB
Transmitter gain temp
dependence
2
I
L
= 20 mA, 0-50
C
-1
+1
dB
Transmitter attenuation in
mute mode
2
60
dB
Transmitter frequencey response
2
200 Hz - 3.4 kHz
-1
+1
dB
Receiver gain
2
20
10
log(V
4
/ V
1
),1 kHz
I
L
= 57 mA
-17.9
-16.5
-15.1
dB
R
L
= 0
-18.5
-16.5
-14.5
dB
R
L
= 900
- 2.2 k
-13.5
-11.5
-9.5
dB
I
L
= 20 mA
-12.5
-11.5
-10.5
dB
Receiver gain temp dependence
2
I
L
= 20 mA, 0 - 50
C
-1
+1
dB
Receiver tone gain
2
20
10
log (V
4
/ V
5
), 1 kHz
I
L
= 25 mA
4.5
6
7.5
dB
Receiver frequency response
2
200 Hz - 3.4 kHz
-1
+1
dB
Microphone input impedance
2
1 kHz
1.3
1.7
2.1
k
(Differential)
Transmitter input impedance
Pin 3
4
1 kHz
13
17
21
k
Transmitter dynamic output
voltage
2
200 Hz - 3.4 kHz < 10% distortion
I
L
= 20 mA - 100 mA
1.8
Vp
I
L
= 16mA, V
DC
= 4.5V, I
DC
= 12mA
1.4
Vp
I
L
= 16mA, V
DC
= 4.0V, I
DC
= 10mA
1.8
Vp
Transmitter Max. output voltage
2
200 Hz - 3.4 kHz, V
3
= 0 - 1Vrms
I
L
= 0 mA - 100 mA
3
Vp
Receiver input impedance
Pin 15
4
1 kHz
28
35
42
k
Receiver tone input impedance
Pin 17
2
1 kHz, Not mute. Note 1
7.0
8.8
11
k
Receiver output impedance
2
1 kHz
6
Ref
PBL 3853
4
Parameter
Symbol
fig.
Conditions
Min.
Typ.
Max.
Unit
Receiver dynamic output
voltage
2
200 Hz - 3.4 kHz< 2% distortion
I
L
= 20 mA - 100 mA
0.6
Vp
Zrec = 150
0.25
Vp
Receiver Max. output voltage
3
Measured with rectifier
200 Hz - 3.4 kHz
I
L
= 0 mA - 100 mA
V
1
= 0 -50 Vrms
0.8
Vp
Transmitter output noise
2
Psoph - weighted rel. 1 V
R
L
= 900
-74
dB
Psoph
Receiver output noise
2
Psoph - weighted rel. 1 V, with cable:
-80
dB
Psoph
0 - 5 km, = 0.5 mm
0 - 3 km, = 0.4 mm
Mute input voltage at mute
(transmit)
V
M
2
2
V
Input voltage at cut off
(receive)
V
M
2
Note1
3
V
DC-supply current
2
I
L
= 16 mA, V
DC
= 4.5 V
12
mA
Note: 1. This input has three functions (see page 7). No input should be set on higher level than +V.
Ref
PBL 3853
5
Pin Description
DIP
SO
Symbol
1
1
+L
Output of the transmitter (+Line side)
2
2
TO
Output of the transmitter (side tone signal)
3
3
TI
Input of the transmitter amplifier
4
4
+C
The circuit supply (sinks ~ 0,3 mA)
5
5
DCAC
Adjustment for DC-char. and AC imp. to line
6
6
GR
Gain regulation starting point setting
7
7
T2
Output for transistor 2, active when voltage on the line is too low for VDC
8
8
T1
Output for transistor 1, active when charging current into VDC's reservoir capacitor
9
9
FE
Feedback
10
NC
No connection
11
NC
No connection
10
12
TM
Transmitter mute input
11
13
MO
Microphone amplifier output
12
14
MI
1
Microphone amplifier inverting input
13
15
MI
2
Microphone amplifier non inverting input
14
16
-L
Negative terminal of the circuit
15
17
RI
1
Receiver amplifier input (gain control)
16
18
RO
Receiver amplifier output
17
19
RI
2
Receiver amplifier input for cut-off, see page 7.
18
20
VDC
VDC supply terminal
Figure 5. Pin configuration.
18 pin-DIP
20 pin-SO
+L
TO
TI
+C
DCAC
GR
T2
T1
RO
RI 1
-L
MI 2
MI 1
MO
1
2
3
4
5
6
7
8
16
15
14
13
12
11
FE
TM
9
10
VDC
RI 2
18
17
1
2
3
4
5
6
7
8
20
19
18
17
16
15
14
13
+L
TO
TI
+C
DCAC
GR
T2
T1
VDC
RI2
RO
RI1
-L
MI 2
MI 1
MO
9
12
10
11
FE
NC
TM
NC
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