PBL 385 73
June 1999
PBL 385 73
Speech Circuit for constant current
feeding systems
Description.
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.
Key features.
•
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.
•
•
•
•
•
•
•
1
9
MIC.
10
DC-supply
•
•
•
13
AR
PBL 385 73
AM
AT
REC
14
6
5
8
3
2
12
11
+4
Telephone
line
7
Mute
(active low)
DTMF - input
4
5
DC supply for
external devices
2
+
3
+
1
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.
1
P
14-pin plastic DIP
B
L
38
5
73
14-pin plastic SO
PB
L
38
5
73
ERICSSON [ ERICSSON ]
