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參數(shù)資料
| 型號： | HM9270D |
| 廠商： | ELAN Microelctronics Corp . |
| 英文描述： | DTMF RECEIVER |
| 中文描述： | 雙音多頻接收器 |
| 文件頁數(shù)： | 6/10頁 |
| 文件大?。?/td> | 66K |
| 代理商： | HM9270D |
DTMF RECEIVER
HM 9270C/D
- 6 -
The HM9270C/D monolithic DTMF receiver offers small size, low power consumption and high performance. Its
architecture consists of a bandsplit filter section, which separates the high and low tones of receiver pair, followed by
a digital counting section which verifies the frequency and duration of the received tones before passing the
corresponding code to the output bus.
FILTER SECTION
Separation of the low-group and high-group tones is achieved by applying the dual tone signal to the inputs of two
filters a sixth order for the high group and an eighth order for the low group. The bandwidths of which correspond
to the bands enclosing the low-group and high-group tones (see Fig. 4). The filter section also in corporates
notches at 350Hz and 440 Hz for exceptional dial-tone rejection. Each filter output is followed by a second-order
switched-capacitor section which smooths the signals prior to limiting. Limiting is performed by high-gain com-
parators which are provided with hysteresis to prevent detection of unwanted low-level signals and noise; the
outputs of the comparators provide full-rail logic swings at the frequencies of the incoming tones.
Flow Fhigh KEY TOE Q4
697 1209 1 H
697 1336 2 H
697 1477 3 H
770 1209 4 H
770 1336 5 H
770 1477 6 H
852 1209 7 H
852 1336 8 H
852 1477 9 H
941 1336 0 H
941 1209 * H
941 1477 # H
697 1633 A H
770 1633 B H
852 1633 C H
941 1633 D H
- - ANY L
L = LOGIC LOW , H = LOGIC HIGH, Z = HIGH
IMPEDANCE
FIGURE 4. LOGIC TABLE
Q3
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
Z
Q2
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
Z
Q1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
Z
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
Z
FIGURE 3. SINGLE ENDED INPUT CONFIGURATION
Decoder Section
The decoder used digital counting techniques to
determine the frequencies of the limited tones and to
verify that they correspond to standard DTMF
frequencies. A complex averaging algorithm(protects)
against tone simulation by extraneous signals, such as
voice, while providing tolerance to smalll frequency
deviations and variations. This averaging algorithm has
been developed to ensure an optimum combination of
immunity to "talk-off" and tolerance to the presence of
interfering signals ("third tones") and noise. When the
detector recognizes the simultaneous presence of two
valid tones (referred to as "signal condition" in some
industry specifications), it raises the "early steering"
flag (ESt). Any subsequent loss of signal condition will
cause ESt to fall.
HM9270D
300
IN+
IN
GS
INH
PWDN
OSC1
OSC2
V
SS
TOE
StD
St/GT
ESt
K
100
NF
Q4
Q3
Q2
Q1
V
DD
V
REF
100
NF
100
100
3.58
MHz
K
K
5V
0.1
μ
f
Vin
5V
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