TELEFUNKEN Semiconductors

U3810BM

Rev. A1: 19.01.1996

8 (31)

Pin description

Pin

Symbol

Function

16

GND

Ground.

17

RREF

External reference resistor. Connection for external reference resistor to generate the

reference current. All basic currents of the circuit which must satisfy certain absolute

accuracy requirements depend on this current.

18

CEI

Capacitor for electronic inductance. Connection for capacitor of the electronic coil.

The circuit contains a first order RC-active low-pass filter. The capacitor is connected

externally between CEI and VL.

19

RDC

DC characteristic slope adjustment. A voltage across resistor RDC is proportional to

the dc line voltage. This means the current flow through RDC is also proportional to

the line voltage. This current drives the supply currents drawn from VL by the most

important loads, and therefore defines the total current consumption of the circuit.

Adjustment to the slope characteristic is realized by modification of RDC resistance.

20

AGA

Line length adjustment. Reference voltage level for AGA. The potential at this point

defines the start threshold for the AGA and the automatic balancing in the receive part

(both can be switched off by the serial bus). The potential is normally formed between

VCC and ground using a voltage divider. When the line voltage exceeds the threshold

level, the AGA or balancing becomes effective.

21

MICX

Asymmetrical microphone input for special applications. The input of the first stage of

the transmit amplifier, selected by the serial bus. Anticlipping is not effective at this

input.

22

MIC1

Inverting input of microphone amplifier.

23

MIC2

Noninverting input of microphone amplifier.

24

ZAC

AC impedance adjustment. Adjustment of the ac circuit impedance to the line by

changing of RZAC.

25

TO

Transmit amplifier output. Transmit amplifier output modulates the current flowing

into this output (typically 4.8 mA).

26

MICO

Microphone amplifier output. Output MICO; open-circuit potential = 2*Vbe

27

TIN

Transmit and DTMF input. Input of the second transmit stage.

28

TACL

Adjustment of anticlipping time constant with external RC combination. Anticlipping

controls the transmitter input level to prevent clipping with high signal levels. The

dynamic range of the transmit peak limiter is controlled by an internal circuit.

29

RECO2

Symmetrical output of receive amplifier.

30

RECO1

Symmetrical output of receive amplifier.

31

RECOX

Receive amplifier output for handsfree and answering machine applications.

32

STL

Long line sidetone network.

33

RECI

Receive amplifier input. It is driven by a signal from VL.

34

STS

Short line sidetone network.

35

MF

Multifrequency output. Output DTMF signal and confidence tone in pulse–density

modulated form. DTMF signal and confidence tone are generated by special generators

in the digital part of the circuit. The DTMF signal consists of two weighted and

superimposed pulse-density modulated signals, while in the case of confidence tone, a

pulse–density modulated signal is superimposed on a high frequency rectangular–pulse

signal with pulse duty factor 0.5. The superimposed signals are sent out to MF for

further processing.

36

D

Data input of serial bus (see Pin 37). Serial data input from microprocessor for

programming the circuit.