CPC5712
3. Design Example
An application circuit that is based on information
discussed in Section 2.5 “Detector Threshold
Operation” on page 6 is shown in Figure 2.
LIU detector will monitor the Public Switched
Telephone Network (PSTN) twisted pair TIP and RING
leads for a voltage level that indicates a device on the
line is off-hook while the LOOP detector monitors for
the presence of battery feed. In this example
detector 2 (DET2) will be the LIU detector as it has the
greater voltage detect thresholds.
In the following telephony design example, it is desired
to have a Line-In-Use (LIU) detector set at 12V with a
hysteresis of 3V, and a loop or battery-presence
(LOOP) detector set at 5V with a hysteresis of 2V. The
Figure 2 CPC5712 Application Circuit
V+
0.1µF
1
VCC
CPC5712
OUT+
OUT -
5
6
+ Analog Output
− Analog Output
7
8
IN+
IN-
TIP
+
806K
1%
G = 5
RING
-
(4)
10M
1%
POLARITY
DET1
4
3
2
Polarity Output
OUT+
1206
Voltage Level Detect 1
Voltage Level Detect 2
DET2
VREF
VL1
VH1 VL2
VH2
GND
16 15
14
9
10
11
12
13
R1
26.7K
1%
R2
17.8K 61.9K 26.7K 137K
1% 1% 1% 1%
R3
R4
R5
R01
www.clare.com
7
CLARE [ CLARE ]
