CD22204_02 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
8
V_DD
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
coupled, as long as it does not exceed the positive supply
voltage. 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
waveforms, 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
television “color-burst” (3.579545MHz) crystal. The crystal
oscillator 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 frequency 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.
3