5

7

RO1

RO2

OUT1

2

OUT2

CS

CO1

CO2

CS

LINE FEEDER

L3235

GND

-VBAT

TIP

RING

LINE TERMINALS

A

B

VA

RINGING INJECTOR

L3234

643

1

CA

VA

C100

CVCC

VCC

GND

V100

+5V

GND

+100V

D94TL132

Figure 3: L3234/L3235 Circuit Configuration

When the ringing function is selected by the sub-

scriber card, a low level signal is continuously ap-

plied to pin 1 through a de coupling capacitor. Then

the logical ring drive signal CS provided by L3235 is

applied to pin 2 with a cadenced mode.

The ringing cycles are synchronised by the L3234

in such a way that the ringing starts and stops al-

ways when the analog input signal crosses zero.

When the ringing injection is enabled (CS = ”1”),

an AC ringing signal is injected in a balanced

mode into the telephone line.

When the ringing injection is disabled (CS = ”0”),

the output voltage on OUT2 raises to the high

power supply, whereas on OUT1, it falls down to

ground.

The L3234 has a low output impedance when

sending the signal, and high output impedance

when the ringing signal is disabled

In fig. 4 the dynamic features of L3234 are

shown.

OPERATION DESCRIPTION

The Fig. 3 show the simplified circuit configuration

of the L3234 Solid State Ringing injector when

used with the L3235 Line Feeder.

EXTERNAL COMPONENTS LIST

In the following table are shown the recommended external components values for L3234.

Ref.

Value

Involved Parameter or Functi on

R01, R02

82

Ω

Ringing Feeding Series Resistors

C01, C02

10

µF - 160V

Ringing Feeding De coupling Capacitors

CA

4.7

µF - 10V

Low Level Ringing Signal De coupling Capacitor

C100

100nF - 100V

Positive Battery Filter

100nF

+5V Supply Filter

L3234 - L3235

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