Calling Line Identifier
MX602 - PRELIMINARY INFORMATION
7
The Input Signal Amplifier may also be used, with different external components, to allow the MX602 to operate from an
unbalanced signal source as shown in Figure 4. In this unbalanced signal configuration, the values of R6 and R8 are the
same as used for the balanced input configuration @ 3.3V nominal.
AMPOUT
C6
R6
R8
IN-
-
A
IN+
+
V
BIAS
Input Signal
Amplifier
V
SS
C9
Figure 4: Input Signal Amplifier, unbalanced input configuration
1000
900
800
700
600
500
400
300
200
100
0
R8
R9
3
3.5
4
4.5
5
5.5
V
DD
Figure 5: Input Signal Amplifier, optimum values of R8 and R9 vs. V
DD
4.3 Bandpass Filter
Is used to attenuate out of band noise and interfering signals from reaching the FSK Demodulator, Tone Alert Detector
and Level Detector circuits. The characteristics of this filter, differs between FSK and Tone Alert modes. Switched
Capacitor filter stages clocked at 57.7kHz provide primary filtering. If the input signal is band limited to 28.85kHz then no
anti-aliasing filtering is required.
4.4 Level Detector
This block operates by measuring the level of the signal at the output of the Bandpass Filter. It then compares it against a
threshold which depends on whether FSK Receive or Tone Alert Detect mode has been selected.
In Tone Alert Detect mode the output of the Level Detector block provides an input to the Tone Alert Signal Detector.
In FSK Receive mode the MX602 DET output will be set high when the level has exceeded the threshold for a sufficient
duration. Amplitude and time hysteresis are used to reduce chattering of the DET output in marginal conditions.
Note: In FSK Receive mode, this circuit may also respond to non-FSK signals such as speech.
© 1998 MX•COM Inc.
www.mxcom.com Tele: 800 638-5577 336 744-5050 Fax: 336 744-5054
Doc. # 20480136.004
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by their respective companies.
CMLMICRO [ CML MICROCIRCUITS ]
