* This specification are subject to be changed without notice.

AG8889

CALL WAITING DECODER

2

8.8.2000

V.

FUNCTIONAL BLOCK DIAGRAM

VI. PIN DESCRIPTIONS

Pin

I/O

Description

TIP

I

Tip in should be connected with twisted pair

RING

I

Ring in should be connected with twisted pair

OPO

O

Output of OP Amp

VREF

Reference voltage Vref = 1/2 Vdd

PWD

I

This pin is normal low enabling chip on normal operation and ready to detect CAS

tone signals.

This active high input sets the chip into power down mode and disable oscillator to

save power.

OSCI

I

3.58MHz oscillator in

OSCO

O

3.58MHz oscillator out

DO

O

DO : used as output, this pin determines whether DO signal is valid or not. High is

valid. Normal low.

VDD

Power

GND

Ground

NC

Non connected

VII. FUNCTIONAL DESCRIPTIONS

Call Waiting service works by alerting a customer engaged in a telephone call to a new incoming call. This way the

customer can still receive important calls while engaged in a current call. The CALL WAITING DECODER can detect

CAS(Call-Waiting Alerting Signal 2130Hz plus 2750Hz) and generate a valid signal on the data pin.

The call waiting decoder is designed to support the Caller Number Deliver feature, which is offered by regional Bell

Operating Companies. The call waiting decoder has three blocks, including differential amplifier, tone filter detection block

In a typical application, this IC receives Tip and Ring signals from twisted pairs. The signals as inputs of differential

amplifier, and the differential amplifier sends input signal to a band pass tone filter. Once the signal is filtered, the

digital detection block decodes the information. The output data made available at DO pin.

This IC is used for detecting CAS signals. Once the signal is detected, the detection indication is shown on the data

output DO pin. The DO pin is normal low. When this IC detects 2130Hz and 2750Hz frequency at the same time, then

DO pin goes to high.

TIP

Filter

Vdd/2

Voltage

Reference

Clock

Generator

DO

OPO

Tone

Detection Block

VREF

PWD

OSCI OSCO

RING