PBL 385 41
November 1998
PBL 385 41
Universal Speech Circuit
Description.
PBL 38541 is a monolithic integrated speech transmission circuit for use in
electronic telephones or in any other line interface application. High settable supply
current for auxiliary functions, up to 6.0 mA (at high line currents). The circuit is designed
to accomodate either a low impedance dynamic or an electret microphone. Microphone
can be muted separately. Payphone signaling and DTMF dialling tones have a separate
input that is controlled by a mute signal. A signal summing point is available at the
transmitter input. An internally preset line length compensation can be adjusted with
external resistors to fit into different current feed systems as for ex. 48 V, 2 x 200 ohms,
48 V, 2 x 400 ohms and 48 V, 2 x 800 ohms. The line length compensation can be shut
off in either high or low gain mode. 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. The circuit provides four different DC - supplies to feed
microphones,diallers and other more current consuming functions like handsfree systems.
Pin numbers in this datasheet refer to 18-pin DIP package unless otherwhise noted.
Key features.
•
Minimum number of external
components, with two filtered DC-
supplies, 7 capacitors and 11
resistors.
Easy adaption to various market
needs.
Mute control input for operation with
DTMF - generator.
A separate signaling input for
payphone and DTMF tones controlled
by mute.
Transmitter and receiver gain
regulation for automatic loop loss
compensation.
Extended current and voltage range
4 - 130 mA, down to 2 .2V.
Differential microphone input for good
balance to ground.
Balanced receiver output stage.
One stabilized DC - supply for low
current CMOS diallers and or electret
microphones. One settable current
limited supply with 6 mA max. current.
Short start up time.
Excellent RFI performance.
18 - pin DIP and 20 - pin SO packages.
•
•
•
•
•
•
•
•
1
DTMF
input
10
PBL 385 41
AD
AT
AR
17
12
Mic.
13
DC-supply
AM
18
•
•
•
Telephone
line
8
9
7
6
5
11
3
2
15
16
14
+
4
Mute
(active low)
DC2 - output for
external devices
+
+
Gain
regulation
2
+
20-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
P
B
L
5
4
3
1
38
DC1- output for
external devices
5
P
B
18-pin plastic DIP
Figure 1. Functional diagram DIP package.
1
L
38
5
41
41
ERICSSON [ ERICSSON ]
