CPC5712

R02

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7

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 1.

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

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.

Figure 1 CPC5712 Application Circuit

DET1

DET2

POLARITY

+

-

IN+

IN-

OUT+

TIP

RING

OUT -

OUT+

V

CC

10

13

12

11

9

1

14

7

8

4

5

6

3

2

R1

R5

R4

R3

R2

V

REF

V

L1

V

H1

V

L2

V

H2

G = 5

CPC5712

V+

Voltage Level Detect 2

Voltage Level Detect 1

Polarity Output

+ Analog Output

− Analog Output

(4)

10M

1%

1206

GND

15

16

806K

1%

26.7K

1%

137K

1%

26.7K

1%

61.9K

1%

17.8K

1%

0.1

µF