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CPC5710N_1 Datasheet, PDF (7/10 Pages) Clare, Inc. – Phone Line Monitor (PLM) IC | |||
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3. Applications
CPC5710N
3.1 Line-In-Use (LIU) and Line Polarity Detector
This circuit performs two phone line interface
functions, LIU and line polarity detection. The LIU
output is logic high if the tip to ring voltage is less than
approximately 17V. This will occur whenever a parallel
device on the line such as a telephone or FAX is taken
off hook. This circuit can also be used to detect for the
presence or loss of battery.
The Polarity output indicates the polarity of the phone
line. Whenever tip is positive with respect to ring,
Polarity out will be a logic high.
Figure 5. LIU and Polarity Detection Application Circuit
VDD
3
50kâ¦
LIN/CMP
VDD
TIP R1 R2
6 IN+
R5
R3 R4 604Kâ¦
IN-
RING
7
R1-4
8.06Mâ¦
1%
1206
VSS
U1 CPC5710
+
-
1.625 V
-
+
++
AV=6
--
+
-
1.25 V
VDD
VDD
+V
1
CMPOUT 2
0V
LINOUT+ 5
2V
LINOUT- 4
Switch shown
in Linear Mode
GND 8
GND
Unless noted otherwise:
All resistors 1%, 1/16 W.
All capacitors 16 V 10%.
+V
R13
20Kâ¦
R14
4.7Mâ¦
R16
10Kâ¦
+V
IN+
1/4 U2
LM339
OUT
IN-
+V
Polarity
R12
20Kâ¦
R11
499Kâ¦
R8
20Kâ¦
R9
499Kâ¦
R17
4.7Mâ¦
+V
IN+
1/4 U2
LM339
OUT
IN-
R10
21Kâ¦
R6
4.7Mâ¦
+V
IN+
1/4 U2
LM339
OUT
IN-
R7
21Kâ¦
R15
10Kâ¦
LIU
C1
1nF
R02
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