4-245
Description
The CD22202 and CD22203 complete dual-tone multiple
frequency (DTMF) receivers detect a selectable group of 12
or 16 standard digits. No front-end pre-filtering is needed.
The only externally required components are an inexpensive
3.579545MHz TV "colorburst'' crystal (for frequency refer-
ence) and a bias resistor. Extremely high system density is
possible through the use of the clock output of a crystal con-
nected CD22202/CD22203 receiver to drive the time bases
of additional receivers. This is a monolithic integrated circuit
fabricated with low-power, complementary symmetry CMOS
processing. It only requires a single low tolerance power
supply.
The CD22202 and CD22203 employ state-of-the-art circuit
technology to combine the digital and analog functions on
the same CMOS chip using a standard digital semiconductor
process. The analog input is preprocessed by 60Hz reject
and band splitting filters and then hard limited to provide
AGC. Eight Bandpass filters detect the individual tones. The
digital post processor times the tone durations and provides
the correctly coded digital outputs. Outputs interface directly
to standard CMOS circuitry and are three-state enabled to
facilitate bus oriented architectures.
January 1997
Pinout
CD22202, CD22203
(PDIP)
TOP VIEW
D1
EN
IN1633
XEN
ANALOG IN
10
11
12
13
14
15
16
17
18
9
8
7
6
5
4
3
2
1
D2
D4
D8
CLRDV
DV
ATB
XIN
XOUT
V
DD
V
SS
V
SS
HEX/B28
ED (203 ONLY),
NC (202)
Functional Diagram
HIGH B/P
FILTERS
LOW B/P
FILTERS
VOLTAGE
REG./REF.
CLOCK
GENERA
T
O
R
CHIP
CLOCKS
ATB
XEN
INI633
13
8
12
11
5
10
7
4
DETECT
ORS AND SIGNAL-
PR
OCESSING CIRCUITS
6
15
14
2
1
18
17
16
3
CLRDV
DV
D1
D2
D4
D8
EN
XIN
XOUT
HEX/B28
ED-203
NC-202
V
SS
V
DD
PREPR
OCESSOR/
B
ANDSPLIT FIL
TER
ANALOG IN
9
Features
Central Office Quality
No Front End Band Splitting Filters Required
Single, Low Tolerance, 5V Supply
Detects Either 12 or 16 Standard DTMF Digits
Uses Inexpensive 3.579545MHz Crystal for Reference
Excellent Speech Immunity
Output in Either 4-Bit Hexadecimal Code or Binary
Coded 2-of-8
Synchronous or Handshake Interface
Three-State Outputs
Excellent Latch-Up Immunity
Ordering Information
PART
NUMBER
TEMP.
RANGE (
o
C)
PACKAGE
PKG. NO.
CD22202E
0 to 70
18 Ld PDIP
E18.3
CD22203E
0 to 70
18 Ld PDIP
E18.3
File Number
1695.3
DTMF Receivers/Generators
CD22202, CD22203
5V Low Power DTMF Receiver
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
http://www.intersil.com or 407-727-9207
|
Copyright
Intersil Corporation 1999
4-246
CD22202, CD22203
Absolute Maximum Ratings
Thermal Information
DC Supply Voltage (V
DD
)(Referenced to V
SS
Terminal). . . . . . . . 7V
Power Dissipation
T
A
= 25
o
C (Derate above T
A
= 25
o
C at 6.25mW/
o
C. . . . . . . . 65mW
Input Voltage Range
All Inputs Except Analog In . . . . . . . . . . . . . . (V
DD
+0.5V) to -0.5V
Analog in Voltage Range . . . . . . . . . . . . (V
DD
+0.5V) to (V
DD
-10V)
DC Current into any Input or Output
. . . . . . . . . . . . . . . . . . . . . .
20mA
NOTE: Unused inputs must be connected to V
DD
or V
SS
as appropriate.
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 175
o
C
Maximum Junction Temperature (Plastic) . . . . . . . . . . . . . . . . 150
o
C
Maximum Storage Temperature Range . . . . . . . . . . -65
o
C to 150
o
C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300
o
C
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . 0
o
C to 70
o
C
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation
of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
Electrical Specifications
0
o
C
T
A
+70
o
C, V
DD
= 5V
10%
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Frequency Detect Bandwidth
(1.5 + 2Hz)
2.3
3.5
% of f
O
Amplitude for Detection
Each Tone
-32
-
-2
dBm Referenced to 600
Minimum Acceptable Twist
-10
-
+10
dB
60Hz Tolerance
-
-
0.8
V
RMS
Dial Tone Tolerance
"Precise" Dial Tone
-
-
0
dB Referenced to Lower
Amplitude Tone
Talk Off
MITEL Tape #CM7291
-
2
-
Hits
Digital Outputs (except XOUT)
"0" Level, 400
A Load
0
-
0.5
V
"1" Level, 200
A Load
V
DD
-0.5
-
V
DD
V
Digital Inputs
"0" Level
0
-
0.3V
DD
V
"1" Level
0.7V
DD
-
V
DD
V
Supply Current
T
A
= +25
o
C
-
10
16
mA
Noise Tolerance
MITEL Tape #CM7291
(Note 1)
-
-
-12
dB Referenced to Lowest
Amplitude Tone
Input Impedance
V
DD
V
IN
(V
DD
-10)
100k
//15pF
300k
-
NOTE:
1. Bandwidth limited (3kHz) Gaussian noise.
Tw ist
High To ne
Low To ne
----------------------------
=
4-247
CD22202, CD22203
Functional Block Diagram
8
60Hz
REJECT
CLOCK
GENERATOR
CHIP CLOCKS
PRE EMP
POWER REGULATOR
5
10
7
V
DD
V
SS
V
SS
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
DV
STROBE
DATA STROBE
DV
F.F
CLR
CD22202
CD22203
EARLY
DETECT
OUTPUT
CLRDV
6
15
14
2
1
18
17
16
3
4
DATA CLEAR
IN1633
DV
H/B28
D1
D2
D4
D8
EN
NOTE: Pin 6: Early detect output on CD22203 only.
ANALOG
IN
PREPROCESSOR
9
BS1
BS2
12
11
13
8
ATB
XEN
XIN
XOUT
1M
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
9
V
SS
V
DD
10pF
>100k
(ON CHIP)
270k
33k
ANALOG
IN
1500pF
OPTIONAL
HIGH FREQUENCY
NOISE FILTER
(f
C
= 3.9kHz)
AUDIO
INPUT
(+4dBm
MAXIMUM)
0.01
F
CD22202, CD22203
The CD22202 and CD22203 are designed to accept sinuso-
idal input waveforms, but will operate satisfactorily with any
input that has the correct fundamental frequency with har-
monics that are at least 20dB below the fundamental.
Crystal Oscillator
The CD22202 and CD22203 contain 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 crys-
tal is connected between XIN and XOUT. A 1M
resistor is
also connected between these pins in this mode. ATB is a
clock frequency output. Other CD22202 and CD22203
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 CD22202 and CD22203 as shown
in Figure 2.
4-248
CD22202, CD22203
FIGURE 2. CRYSTAL OSCILLATOR
HEX/B28
This pin selects the format of the digital output code. When
HEX/B28 is tied high, the output is hexadecimal. When tied
low, the output is binary coded 2-of-8. The following table
describes the two output codes.
ED
This pin, on the CD22203 only, indicates the presence of fre-
quencies which are likely to be DTMF digits, but have not yet
been verified by a DV signal. It is comparable to a "button-
down" output, and it is useful as an EARLY DETECT signal to
interrupt a microprocessor for digit storage and validation.
DV and CLRDV
DV signals a detection by going high after a valid tone pair is
sensed and decoded at the output pins D1, D2, D4, and D8.
DV remains high until a valid pause occurs or CLRDV is
raised high, whichever is sooner. This handshake can save
microprocessor time.
DTMF Dialing Matrix
IN1633
When tied high, this pin inhibits detection of tone pairs con-
taining the 1633Hz component. For detection of all 16 stan-
dard digits, IN1633 must be tied low.
N/C Pin
This pin has no internal connection and should be left floating.
Digital Inputs and Outputs
All digital inputs and outputs of the DTMF receivers are rep-
resented by the schematic below. Only the "analog in" pin is
different, and is described above. Care must be exercised
not to exceed the voltage or current ratings on these pins as
listed in the "maximum ratings" section.
FIGURE 3. DIGITAL INPUTS AND OUTPUTS
Input Filter
The CD22202 and CD22203 will tolerate total input noise of
a maximum of 12dB below the lowest amplitude tone. For
most telephone applications, the combination of the high
frequency attenuation of the telephone line and internal
band limiting make special circuitry at the input to these
receivers unnecessary. However, noise near the 56kHz
internal sampling frequency will be aliased (folded back)
into the audio spectrum, so if excessive noise is present
TABLE 1. OUTPUT CODES
DIGIT
HEXADECIMAL
BINARY CODED 2-OF-8
D8
D4
D2
D1
D8
D4
D2
D1
1
0
0
0
1
0
0
0
0
2
0
0
1
0
0
0
0
1
3
0
0
1
1
0
0
1
0
4
0
1
0
0
0
1
0
0
5
0
1
0
1
0
1
0
1
6
0
1
1
0
0
1
1
0
7
0
1
1
1
1
0
0
0
8
1
0
0
0
1
0
0
1
9
1
0
0
1
1
0
1
0
0
1
0
1
0
1
1
0
1
*
1
0
1
1
1
1
0
0
#
1
1
0
0
1
1
1
0
A
1
1
0
1
0
0
1
1
B
1
1
1
0
0
1
1
1
C
1
1
1
1
1
0
1
1
D
0
0
0
0
1
1
1
1
XEN
XEN
CD22202/22203
12
11
8
13
ATB
XIN
3.579545MHz
V
DD
XOUT
1M
12
13
8
XIN CONNECTED TO V
DD
UP TO 10 DEVICES
CD22202/22203
COL 0
1209Hz
COL 1
1336Hz
COL 2
1477Hz
COL 3
1633Hz
ROW 0
697Hz
ROW 1
770Hz
ROW 2
852Hz
ROW 3
941Hz
NOTE: Column 3 is for special applications and is not normally used
in telephone dialing.
1
2
3
A
4
5
6
B
7
8
9
C
*
0
#
D
V
DD
V
SS
CMOS
DIGITAL
CIRCUITRY
DIGITAL
OUTPUT
DIGITAL
INPUT
4-249
CD22202, CD22203
above 28kHz, the simple RC filter shown below may be
used to band limit the incoming signal. The cut off
frequency is 3.9kHz.
FIGURE 4. FILTER FOR USE IN EXTREME HIGH FREQUENCY
INPUT NOISE ENVIRONMENT
Noise will also be reduced by placing a grounded trace
around XIN and XOUT pins on the circuit board layout when
using a crystal. It is important to note that XOUT is not
intended to drive an additional device. XIN may be driven
externally; in this case, leave XOUT floating.
Timing Waveforms
FIGURE 5.
CD22202
CD22203
33k
0.0015
F
270k
ANALOG
IN
NOISY
SIGNAL
t
ON
t
OFF
PAUSE
ANALOG
INPUT
D1, D2
D4, D8
TONE BURST 1
TONE BURST 2
t
D
t
R
t
SU
t
H
t
CL
t
PW
t
ER
t
ED
CLRDV
DV
ED
NOTE: Early Detect output is available only on the CD22203.
(NOTE)
Guard Time
Whenever the DTMF receiver is continually monitoring a
voice channel containing distorted or musical voices or
tones, additional guard time may be added in order to
prevent false decoding. This may be done in software by
verifying that both ED and DV are present simultaneously for
about 55ms. An appropriate guard time should be selected
to balance the fastest expected dialing speed against the
rejection of distorted or musical voices or tones (most
autodialers operate in the 65ms to 75ms range although a
few generate 50ms tones). A hardware guard time circuit is
shown in Figure 6. R
3
and R
4
should keep the voice
amplitude as low as practical, while R
2
and R
5
adjust
detection speed.
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
Tone Time
For Detection
t
ON
40
-
-
ms
For Rejection
t
ON
-
-
20
ms
Pause Time
For Detection
t
OFF
40
-
-
ms
For Rejection
t
OFF
-
-
20
ms
Detect Time
t
D
25
-
46
ms
Release Time
t
R
35
50
ms
Data Setup Time
t
SU
7
-
-
s
Data Hold Time
t
H
4.2
-
5
ms
DV Clear Time
t
CL
-
160
250
ns
CLRDV Pulse Width
t
PW
200
-
-
ns
ED Detect Time
t
ED
7
-
22
ms
ED Release Time
t
ER
2
-
18
ms
Output Enable Time
C
L
= 50pF, R
L
= 1k
-
-
200
300
ns
Output Disable Time
C
L
= 35pF, R
L
= 500
-
-
150
200
ns
Output Rise Time
C
L
= 50pF
-
-
200
300
ns
Output Fall Time
C
L
= 50pF
-
-
160
250
ns
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