75T204
5V Low-Power Subscriber
DTMF Receiver
April 2000
DESCRIPTION
The 75T204 is a complete Dual-Tone Multifrequency
(DTMF) receiver that detects 16 standard digits. No
front-end pre-filtering is needed. The only external
components required are an inexpensive 3.58-MHz
television 鈥渃olorburst鈥?crystal for frequency reference
and a bias resistor. An Alternate Time Base (ATB)
is provided to permit operation of up to 10 75T204's
from a single crystal. The 75T204 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 signal is pre-processed by 60-Hz reject and
band split 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
(continued)
FEATURES
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Intended for applications with less
requirements than the 75T202/75T203
14-pin plastic DIP or 16-pin SO package for
high system density
NO front-end band-splitting filters required
Single low-tolerance 5-volt supply
Detects all 16 standard DTMF digits.
Uses an inexpensive 3.579545-MHz crystal
Excellent speech immunity
Output in 4-bit hexadecimal code
Three-state outputs for microprocessor
interface
BLOCK DIAGRAM
BANDPASS FILTERS
697
BAND
SPLIT
FILTERS
BS1
ZERO
CROSSING
DETECTORS
AMPLITUDE
DETECTORS
770
PRE-PROCESSOR
ANALOG
60 Hz
REJECT
PREEMP
852
941
TIMING
CIRCUITRY
BS2
1209
1336
DV
DV
XEN
1633
梅8
CLOCK
GENERATOR
DATA STROBE
ATB
1477
XIN
CHIP CLOCKS
D1
1Mz
XOUT
D2
OUTPUT
DECODER
OUTPUT
REGISTER
D4
POWER REGULATOR
VOLTAGE
REF
D8
DATA CLEAR
EN
VP
GND
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英文版
5V Low-Power Subscriber DTMF Receiver
ETC
-
英文版
5V Low-Power Subscriber DTMF Receiver
ETC [ETC]
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英文版
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英文版
5V LOW POWER DTMF RECEIVER
ETC [ETC]
-
英文版
5V Low-Power Subscriber DTMF Receiver
ETC
-
英文版
5V Low-Power Subscriber DTMF Receiver
ETC [ETC]
-
英文版
5V Low-Power Subscriber DTMF Receiver
ETC
-
英文版
5V Low-Power Subscriber DTMF Receiver
ETC [ETC]
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英文版
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