CPC5710N Datasheet, PDF (7/10 Pages) Clare, Inc. – Phone Line Monitor (PLM) IC

INTEGRATED CIRCUITS DIVISION
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 4. LIU and Polarity Detection Application Circuit
V_DD
3
50kΩ
LIN/CMP
V_DD
TIP R1 R2
6 IN+
R5
R3 R4 _604KΩ
IN-
RING
7
R1-4
8.06MΩ
1%
1206
V_SS
U1 CPC5710
+
-
1.625 V
-
+
++
A_V=6
--
+
-
1.25 V
V_DD
V_DD
+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
20KΩ
R14
4.7MΩ
R16
10KΩ
+V
IN+
1/4 U2
LM339
OUT
IN-
+V
Polarity
R12
20KΩ
R11
499KΩ
R8
20KΩ
R9
499KΩ
R17
4.7MΩ
+V
IN+
1/4 U2
LM339
OUT
IN-
R10
21KΩ
R6
4.7MΩ
+V
IN+
1/4 U2
LM339
OUT
IN-
R7
21KΩ
R15
10KΩ
LIU
C1
1nF
R03
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