TELEFUNKEN Semiconductors

U3810BM

Rev. A1: 19.01.1996

7 (31)

Pin description

Pin

Symbol

Function

1

RPI

Ringing power information. The RC combination smooths the drive current of the

loudspeaker amplifier.

2

VRI

Tone-ringer supply voltage. The rectified ringing voltage is delivered to VRI and then

converted into the lower supply voltage, VSA, by the converter.

3

IMPA

External adjustment of input ringing impedance. IMPA is adjusted with a resistance

between pin 2 and 3.

ZIN = RIN/100

4

COS

Control output switching supply. COS drives the base of the external switching transis-

tor of the converter.

5

IOS

Current output of switching supply. This output provides a constant current, which

supplies the external part of converter. The magnitude of the current depends on the

VRI voltage and the value of resistance RIN.

6

TAD

Adjustment of antidistortion time constant in loudhearing with external RC

combination.

7

TAL

Adjustment of antilarsen time constant in loudhearing with external RC combination.

8

VDD

External logic supply.

9

VCC

Power supply for peripherals. VCC and VDD are stabilized supply voltages buffered

with external capacitors. They are derived internally from the same voltage source, but

are separated from each other by electronic switches. VDD also supplies the digital

part of the circuit and is achieved in all three modes: speech mode, ringing mode and

operation with external supply. According to the application, peripherial modules are

connected to VDD which, in addition to speech mode, must be supplied at least in one

of the two other modes. The digital part of circuit and microprocessor must continue

operating during line breaks, as they occur during pulse dialing or during flash-signal

transmission. Since VDD in this time intervals is fed only from the buffer capacity, the

power consumption from VDD must not cause the total voltage dump. VCC supplies

no internal parts of circuit and is supplied exclusively in speech mode. External

components, which must operate only in this mode, can be connected here. The power

is drawn only from the relevant buffer capacitor in the supply intervals during pulse

dialing or flash-signal transmission.

10

VL

Line voltage.

11

SAI

Speaker amplifier input. The signal coming from the receive part, e.g. from REC01 or

RECO2, is fed in here.

12

SAIX

Speaker amplifier input for special application i.e. answering machine. SAIX is

selected via the serial bus. SAIX has to be selected for ringing. IF ringing, Antidistor-

tion and Antilarsen are disabled.

13

VSA

Supply voltage for the loudhearing amplifier. Stabilized supply voltage buffered with

an external capacitor for the loudhearing amplifier and zero crossing detector; aditional

connection point for an external supply. In speech mode, VSA is supplied by the

analog part of the circuit. In this case, the stabilization point is adjusted to the DC line

voltage VSA= VL/1.5. In ringing mode, and VSA is supplied directly from the con-

verter. The stabilization point is permanently set. The logic supply, VDD, is fed by a

switch from VSA. VSA=5.2V. In the case of an external supply, VSA serves as a point

for a current from a power supply. The stabilization point of VSA and supply for the

logic correspond to the operation conditions in ringing mode.

14

SO1

Loudspeaker output 1.

15

SO2

Loudspeaker output 2. Differential output of loudhearing amplifier. The loudspeaker

can also be connected asymmetrically to ground or to VSA via a capacitor at one of the

two outputs. As a result of this connection there is a bigger output power in reference

to low line currents and loudspeakers with low impedance, while the differential

connection method results in a higher power output and lower harmonic distortion with

medium or high line currents and/or loudspeaker impedances