69

Functional Block Diagram

System Functions

Analog In

The Analog In pin accepts the analog input. It is internally

biased so that the input signal may be either AC or DC cou-

pled, as long as it does not exceed the positive supply volt-

age. Proper input coupling is illustrated below.

FIGURE 1. ANALOG IN

The CD22204 is designed to accept sinusoidal input wave-

forms, but will operate satisfactorily with any input that has

the correct fundamental frequency with harmonics that are

at least 20dB below the fundamental.

Crystal Oscillator

The CD22204 contains an on-board inverter with sufficient

gain to provide oscillation when connected to a low cost tele-

vision “color-burst” (3.579545MHz) crystal. The crystal oscil-

lator is enabled by tying XEN high. The crystal is connected

between XIN and XOUT. A 1M

Ω resistor is also connected

between these pins in this mode. ATB is a clock frequency

output. Other CD22204 devices may use the same fre-

quency reference by tying their ATB pins to the ATB output of

a crystal connected device. XIN and XEN of the auxiliary

devices must then be tied high and low, respectively. Up to

ten devices may be run from a single crystal connected

CD22204 as shown in Figure 2.

60Hz

REJECT

CLOCK

GENERATOR

CHIP CLOCKS

PRE EMP

POWER REGULATOR

4

8

VOLTAGE

REF

697

770

852

941

1209

1336

1477

1633

BAND

SPLIT

FILTERS

ZERO

CROSSING

DETECTORS

BANDPASS

FILTERS

AMPLITUDE

DETECTORS

OUTPUT

DECODER

OUTPUT

REGISTER

TIMING

CIRCUITRY

DATA STROBE

12

2

1

14

13

3

DATA CLEAR

DV

D1

D2

D4

D8

EN

ANALOG

IN

PREPROCESSOR

7

BS1

BS2

10

9

11

6

ATB

XEN

XIN

XOUT

1M

NOTE: Pin numbers are for plastic DIP.

7

10pF

>100k

Ω

(ON CHIP)

270k

Ω

33k

Ω

ANALOG

IN

1500pF

OPTIONAL

HIGH FREQUENCY

NOISE FILTER

AUDIO

INPUT

(+4dBm OR

0.01

µF

CD22204E

MAXIMUM)

CD22204