February 1999 File Number 1696.4
5V Low Power Subscriber DTMF Receiver
The CD22204 complete dual tone multiple frequency (DTMF)
receiver detects 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 reference) and a bias
resistor. Extremely high system density is possible through
the use of the Alternate Time Base (ATB) output of a crystal
connected CD22204 receiver to drive the time bases of up to
10 additional receivers. This is a monolithic integrated circuit
fabricated with low power, complementary symmetry CMOS
processing. It only requires a single power supply.
The CD22204 employs state-of-the-art ‘‘switched-capacitor’’
filter technology, resulting in approximately 40 poles of filtering
and digital circuitry on the same CMOS chip. The analog input
is preprocessed by 60Hz reject and bandsplitting filters and
then zero-cross detected to provide AGC. Eight bandpass
filters detect the individual tones. Digital processing is used to
measure the tone and pause durations and provides the
correctly coded and timed digital outputs. The outputs
interface directly to standard CMOS circuitry and are three-
state enabled to facilitate bus oriented architectures.
0 to 70 14 Ld PDIP
NOTE: Pin numbers are for PDIP.
• No Front End Band Splitting Filters Required
• Single Low Tolerance 5V Supply
• Three-State Outputs for Microprocessor Based
• Detects all 16 Standard DTMF Digits
• Uses Inexpensive 3.579545MHz Crystal
• Excellent Speech Immunity
• Output in 4-Bit Hexadecimal Code
• Excellent Latch-Up Immunity
67 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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