CD22204 Datasheet, PDF (3/5 Pages) Intersil Corporation – 5V Low Power Subscriber DTMF Receiver

Functional Block Diagram
CD22204
ANALOG
IN
7
PREPROCESSOR
60Hz
REJECT
PRE EMP
ATB ¹¹
XEN ⁶
10
÷8
XIN
1M
XOUT
9
BAND
SPLIT
FILTERS
BS1
ZERO
CROSSING
DETECTORS
BANDPASS
FILTERS
697
770
852
941
BS2
1209
1336
1477
1633
CLOCK
GENERATOR
CHIP CLOCKS
AMPLITUDE
DETECTORS
TIMING
CIRCUITRY
DATA STROBE
POWER REGULATOR
VOLTAGE
REF
OUTPUT
DECODER
OUTPUT
REGISTER
4
V_DD
8
V_SS
NOTE: Pin numbers are for plastic DIP.
DATA CLEAR
DV
12
2 D1
1 D2
14 D4
13 _D8
3 EN
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.
AUDIO
INPUT
(+4dBm OR
1.22V_RMS
MAXIMUM)
0.01µF
1500pF 33kΩ
CD22204E
V_DD
270kΩ
7
ANALOG
IN
(ON CHIP)
10pF
>100kΩ
V_SS
OPTIONAL
HIGH FREQUENCY
NOISE FILTER
(f_C = 3.9kHz)
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 1MΩ 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.
69