* This specification are subject to be changed without notice.

AG8888

CALL WAITING DECODER

2

8.8.2000

V.

FUNCTIONAL BLOCK DIAGRAM

VI. PIN DESCRIPTIONS

Pin

I/O

Description

TI/RI

I

Tip in or Ring in should be connected with twisted pair

OE

I

Output enable for alert tone detected. High is enable. Low is for factory test.

OSCI

I

480KHz crystal in

OSCO

O

480KHz crystal out

DO

O

Alert tone detected output. Normal low.

Under OE pin set to high, when call waiting alert tone is detected, this pin goes to high.

OPO

O

Output of OP Amp

BO

O

Internal buffer output

FI

I

Band pass filer input

AVDD

Analog power.

DVDD

Digital power.

AVSS

Analog Ground.

DVSS

Digital 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. Thus, the

customer can still receive important calls while engaged in a current call. The call waiting decoder can detect alert

tone (Call-Waiting Alerting Signal 2130Hz plus 2750Hz) and generate a valid timing on the data pins.

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 four blocks, including OP Amp, band pass filter, and

detection block.

In a typical application, this IC receives Tip/Ring signals from twisted pairs. The signals as inputs of single-ended

pre-amplifier (OP Amp and Buffer Amp), and the amplifier sends input signal to a band pass filter. Once the

TI/RI

Filter

Vdd/2

Voltage

Reference

Clock

Generator

DO

OPO

Tone

Detection Block

OE

OSCI

OSCO

Buffer

BO

FI