Calling Line Identifier
MX602 - PRELIMINARY INFORMATION
6
4. General Description
4.1 Mode Control Logic
The MX602's operating mode and the source of the DET and IRQ outputs are determined by the logic levels applied to
the MODE and ZP input pins;
ZP MODE
Mode
DET output from
IRQ output from
0
0
1
1
0
1
0
1
Tone Alert Detect Tone Alert Signal Detection
End of Tone Alert Signal Ring or Line
Polarity Reversal Detector
FSK Receive
Zero-Power
Zero-Power
FSK Level Detector
FSK Data Retiming (if enabled) and Ring or
Line Polarity Reversal Detector
Ring or Line Polarity Reversal Ring or Line Polarity Reversal Detector
Detector
Ring or Line Polarity Reversal None
Detector
In the 'Zero-Power' modes, power is removed from all of the internal circuitry except for the Ring or Line Polarity Reversal
Detector and the DET and IRQ outputs.
4.2 Input Signal Amplifier
This amplifier is used to convert the balanced FSK and Tone Alert signals received over the telephone line to an
unbalanced signal of the correct amplitude for the FSK receiver and Tone Alert Detector circuits.
AMPOUT
C6
C7
R8
R6
R7
IN-
A
B
-
IN+
VSS
+
VBIAS
Input Signal
Amplifier
R9
R10
C9
Figure 3: Input Signal Amplifier, balanced input configuration
The design equations for this circuit are:
VAMPOUT
V(B-A)
R8
R6
R8 R10
×
Differential Voltage Gain
=
R9 =
(R8 - R10)
R6 = R7 = 470kΩ
R10 = 160kΩ
The target differential voltage gain depends on the expected signal levels between the A and B wires and the MX602's
internal overload and threshold levels, which are proportional to the supply voltage.
The MX602 has been designed to meet the related specifications when R8 = 470kΩ at V = 3.3V nominal, rising to
DD
680kΩ at V = 5.0V (see note) and R9 = 240kΩ at V = 3.3V dropping to 200kΩ at V = 5.0V as shown in
DD
DD
DD
section 4.2 Figure 5
Notes:
1. The recommended values of R8 were selected for applications in both Bellcore and British Telecom Systems.
Optimum Bellcore-only operation may be achieved by reducing the value of R8 e.g. to 656kΩ @ 5.0V.
© 1998 MX•COM Inc.
www.mxcom.com Tele: 800 638-5577 336 744-5050 Fax: 336 744-5054
Doc. # 20480136.004
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