U4074B

Preliminary Information

TELEFUNKEN Semiconductors

Rev. A1, 06-May-96

3 (6)

Tone ringing

Figure 1

2 kV

93 7575 e

a

b

10

mF

110

0.22

mF

15

25

W

W

W

Figure 2. Test circuit

The bridge push-pull outputs are used for direct

connection of a piezo electric sound transducer with a

typical value of 80 nF. The output stage transistors can

process up to 20 mA in both directions.

The output signal without load is 2

R

i

+

V

V

–1

R

load

W

Volume Adjustment A1, A0

Pin 5 (6), 6 (7)

The ringing volume is adjusted by means of a 2-bit D/A

converter. The maximum volume is achieved with the bit

combination A1 (MSB) = 1 and A0 (LSB) = 1. The

volume can be reduced by approximately 35 dB (A) if a

bit combination of A1 = 0, A0 = 0 is supplied. The volume

is programmed by supplying a ground potential to these

inputs.

Melody, Pin 7 (9)

The melody input inverts the activation phase of the

bridge push-pull output stage. The input is CMOS-

compatible

and

suitable

for

processing

ringing

frequencies.

An external load, such as a microcomputer, can be

and can block up to 6 V in call and idle states. The typical

value of the back-up capacitor is 47

mF.

Frequency Detection 2f, Pin 4 (5)

Frequency detection takes place in the microcomputer.

For this purpose, the output 2f supplies a square wave

signal

with

double

ringing

frequency

to

the

microcomputer. The output signal is CMOS-compatible.

This terminal is highly resistive in idle and call states.

Comparator Threshold Adjustment

TH Pin 3 (4)

The on/ off threshold of the 2f comparator can be adjusted

Bundespost specification this terminal should be open.

Decoupling diode for dc supply.