CPC5710N

Rev. 1.0 12/16/2002

www.clare.com

7

3. Using CPC5710N

3.1 LIN/CMP Input

The LIN/CMP input selects the active output, either

the comparator output CMPOUT or the linear outputs,

LINOUT- and LINOUT+. Set LIN/CMP low for linear

output and high for comparator output. Note that both

outputs cannot be used at once.

With LIN/CMP at logic low (LIN/CMP = 0), the

amplifier outputs are biased at 1 Vdc and CMPOUT is

held high. With LIN/CMP at logic high (LIN/CMP = 1),

LINOUT+ is 0 V and LINOUT- is 2 V.

Figure 5. LIN/CMP Timing for Caller-ID Signal

Reception

3.2 Amplifier Design

Considerations

Amplifier inputs are biased at 1.25 Vdc, the internal

voltage references. The internal common-mode

circuitry maintains the average of the inputs at 1.25

Vdc. For example, if one input reaches 1.3 V, the

common-mode circuit drives the other input to 1.2 V.

3.2.1 Linear Amplifier Gain

Display feature information (caller ID) and voice

signals are coupled through the linear amplifier. In

North America, CID data signals are typically sent

between the first and second ringing signal burst.

Referring to Figure 4, signal gain from tip and ring to

LINOUT+ and LINOUT- is determined by:

where

Clare Application Note AN-117 Customize Caller ID Gain

and Ring Detect Voltage Threshold is a spreadsheet for

trying different component values in this type of circuit.

3.3 Comparator Considerations

3.3.1 Ringing Signal Detection

The CPC5710N comparator is a full-wave

configuration. Ringing signals will assert the output on

positive and negative parts of the ringing waveform.

Hysteresis is employed in the internal comparator

circuit to provide noise immunity. The set-up of the

comparator causes CMPOUT output pulses to remain

low for most of the ringing signal positive and negative

half-cycles. CMPOUT returns high when the ringing

signal is near the zero-voltage crossing.

Figure 6. CMPOUT Relative to Ring Signal

3.3.2 Setting Ring Detection Threshold

The ring detection threshold depends on the

component values of the input network. The values for

these components shown in the typical application

circuits are recommended for typical operation.

Referring to Figure 4, the ring detection threshold can

be changed according to the following formula:

Caller ID data

LIN/CMP

Signal levels not to scale

2s

500 ms

3s

475 ms

2s

()

20

+

()

2

1

()

2

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

+

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

log

=

CMPOUT

Ring Signal

750mV

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





+

()

2

1

()

2

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

+

=