1

PBL 385 41

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.

Figure 1. Functional diagram DIP package.

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.

17

14

2

3

11

12

13

18

16

AM

AT

5

AR

15

4

+

10

AD

1

PBL 385 41

7

9

DTMF

input

+

6

Mic.

8

DC-supply

+

Mute

(active low)

DC 2 - output for

external devices

Telephone

line

5

2

4

3

1

Gain

regulation

DC1- output for

external devices

+

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

November 1998

20-pin plastic SO

18-pin plastic DIP