CPC5620 Datasheet, PDF (11/18 Pages) Clare, Inc. – LITELINK III Phone Line Interface IC (DAA)

CPC5620/CPC5621
typical operation. The ring detection threshold can be
changed according to the following formula:
In North American applications, follow these steps to
receive on-hook caller ID data via the LITELINK RX
outputs:
V_RINGPK
=


7_---5_---R0_----m_3-----V_{--}
(2R₆ + R₃)² + ₍---_π----_f-_R----_I--_N-¹--_G----_C----₇---₎--₂-
1. Detect the first ringing signal outputs on RING.
2. Assert CID low.
3. Process the CID data from the RX outputs.
Clare Application Note AN-117 Customize Caller ID Gain
4. De-assert CID (high or floating).
and Ring Detect Voltage Threshold is a spreadsheet for
trying different component values in this circuit.
Note: Taking LITELINK off-hook (via the OH pin) dis-
Changing the ring detection threshold will also change
the caller ID gain and the timing of the polarity reversal
detection pulse, if used.
y _{3.2.2 Polarity Reversal Detection with}
r ^CPC5621
The full-wave ring detector in the CPC5621 makes it
a ^{possible to detect 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
in ^{host system must be able to discriminate this single}
pulse of approximately 1 msec (using the recom-
mended snoop circuit external components) from a
valid ringing signal.
lim ^{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 con-
e ^{trol of the CID pin. In North America, CID data signals}
are typically sent between the first and second ringing
Pr ^signal.
connects 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 deter-
mined by:
GAIN_CID(dB) = 20log ----------------------------⁶----^R----³----------------------------
(2R₆ + R₃)² + ₍---_π----_f--_C¹----₇---₎--₂-
where ƒ is the frequency of the CID data signal.
The recommended components in the application cir-
cuit yield a gain 0.27 dB at 200 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.
Figure 5. On-hook Caller ID Signal Timing in
North America for CPC5620 (with Half-
wave Ring Detect)
For single-ended snoop circuit output of 0 dBm, set
the total resistance across the series resistors (R6/
R44 and R7/R45) to 1.4 MΩ.
2s 500 ms
3s
475 ms 2s
3.3 Off-Hook Operation
RING First Ring
Caller ID data
Second Ring
CID
Signal levels not to scale
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
signal and coupled across the electrical isolation bar-
rier by a reflective dome.
On the host equipment side of the barrier, the receive
signal is converted by a photodiode into a photocur-
Rev. 0.E
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