CPC5620/CPC5621

R04

www.clare.com

11

The ringing detection threshold depends on the values

components shown in the application circuits are

recommended for typical operation. The ringing

detection threshold can be changed according to the

following formula:

Where:

data sheet.

the application circuits shown in this data sheet.

this data sheet.

Clare Application Note AN-117 Customize Caller ID Gain

and Ring Detect Voltage Threshold is a spreadsheet for

trying different component values in this circuit.

Changing the ringing detection threshold will also

change the caller ID gain and the timing of the polarity

reversal detection pulse, if used.

3.2.2 Polarity Reversal Detection with

CPC5621 in On-hook State

The full-wave ringing detector in the CPC5621 makes

it possible to detect on-hook tip and ring polarity

reversal using the RING output. When the polarity of

tip and ring reverses, a pulse on RING indicates the

event. Your system logic must be able to discriminate

this single pulse of approximately 1 msec (using the

recommended snoop circuit external components)

from a valid ringing signal.

3.2.3 On-hook Caller ID Signal Reception

On-hook caller ID (CID) signals are processed by

LITELINK by coupling the CID data burst through the

snoop circuit to the LITELINK RX outputs under

control of the CID pin. In North America, CID data

signals are typically sent between the first and second

ringing signal.

In North American applications, follow these steps to

receive on-hook caller ID data via the LITELINK RX

outputs:

1.

Detect the first ringing signal outputs on RING.

2.

Assert CID low.

3.

Process the CID data from the RX outputs.

4.

De-assert CID (high or floating).

Note: Taking LITELINK off-hook (via the OH pin)

disconnects the snoop path from both the receive

outputs and the RING output, regardless of the state

of the CID pin.

CID gain from tip and ring to RX+ and RX- is

determined by:

Where:

sheet

the application circuits in this data sheet

sheet

The recommended components in the application

circuit yield a gain 0.27 dB at 2000 Hz. Clare

Application Note AN-117 Customize Caller ID Gain and

Ring Detect Voltage Threshold is a spreadsheet for trying

different component values in this circuit. Changing

the CID gain will also change the ring detection

threshold and the timing of the polarity reversal

detection pulse, if used.

For single-ended receive applications where only one

RX output is used, the snoop circuit gain can be

adjusted back to 0 dB by changing the value of the

snoop series resistors R6, R7, R44 and R45 from

1.8M

Ω to 715kΩ. This change results in negligible

modification to the ringing detect threshold.

3.3 Off-Hook Operation: OH=0

3.3.1 Receive Signal Path

Signals to and from the telephone network appear on

the tip and ring connections of the application circuit.

Receive signals are extracted from transmit signals by

the LITELINK two-wire to four-wire hybrid. Next, the

receive signal is converted to infrared light by the

receive photodiode amplifier and receive path LED.

The intensity of the light is modulated by the receive

750mV

-----------------

⎝⎠

⎛⎞

TOTAL

+

()

2

1

πf

()

2

--------------------------------------

+

=

()

20

TOTAL

+

()

2

1

πfC

SNP

()

2

--------------------------

+

-------------------------------------------------------------------------------------------------

log

=