SC9270C/D 查看數據表（PDF） - Silan Microelectronics
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SC9270C/D Datasheet PDF : 12 Pages
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Silan
Semiconductors
SC9270C/D
FUNCTION DESCRIPTIONS
The SC9270C/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.
1. 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 table 1). 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 smooth the signals prior to limiting. Limiting is performed by high-gain comparators 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
Q3
Q2
Q1
697
1209
1
H
0
0
0
1
697
1336
2
H
0
0
1
0
697
1477
3
H
0
0
1
1
770
1209
4
H
0
1
0
0
770
1336
5
H
0
1
0
1
770
1477
6
H
0
1
1
0
852
1209
7
H
0
1
1
1
852
1336
8
H
1
0
0
0
852
1477
9
H
1
0
0
1
941
1336
0
H
1
0
1
0
941
1209
*
H
1
0
1
1
941
1477
#
H
1
1
0
0
697
1633
A
H
1
1
0
1
770
1633
B
H
1
1
1
0
852
1633
C
H
1
1
1
1
941
1633
D
H
0
0
0
0
--
--
ANY
L
Z
Z
Z
Z
L=LOGIC LOW, H=LOGIC HIGH, Z=HIGH IMPEDANCE
Table 1: Function decode table
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.1 2001.04.27
8
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