CPC5622 Datasheet, PDF (11/18 Pages) Clare, Inc. – LITELINK® III Phone Line Interface IC (DAA)

INTEGRATED CIRCUITS DIVISION
will output one logic low pulse per cycle of the ringing
frequency. Also, because the RING2 is the output of a
full-wave detector it will output two logic low pulses
per cycle of the ringing frequency. Hence, the
nomenclature RING2 for twice the output pulses.
The set-up of the ringing detector comparator causes
the RING output pulses to remain low for most of one
half-cycle of the ringing signal and remains high for the
entire second half-cycle of the ringing signal. For the
RING2 output, the pulses remain low during most of
both halves of the ringing cycle and returns high for
only a short period near the zero-crossing of the
ringing signal. Both of the ringing outputs remain high
during the silent interval between ringing bursts.
Hysteresis is employed in the LITELINK ringing
detector circuit to improve noise immunity.
The ringing detection threshold depends on the values
of R3 (R_SNPD), R6 & R44 (R_SNP-), R7 & R45 (R_SNP+),
C7 (C_SNP-), and C8 (C_SNP+). The value of these
components shown in the application circuits are
recommended for typical operation. The ringing
detection threshold can be changed according to the
following formula:
V_RINGPK
=


7-_{R---5-S--0-N--}m_-P---D-V_{--}
R_SNPTOTAL + R_SNPD² + _---_----_f--_R---_I--_N---_G-1---_C----_S---_N---_P---_---₂
Where:
• R_SNPD = R3 in the application circuits shown in this
data sheet.
• RSNP_TOTAL = the total of R6, R7, R44, and R45 in
the application circuits shown in this data sheet.
• C_SNP = C7 = C8 in the application circuits shown in
this data sheet.
• And ƒ_RING is the frequency of the ringing signal.
IXYS Integrated Circuits Division 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.
CPC5622
3.2.2 Polarity Reversal Detection in On-hook
State
The full-wave ringing detector in the CPC5622 makes
it possible to detect an on-hook tip and ring battery
polarity reversal using the RING2 output. When the
polarity of the battery voltage applied to tip and ring
reverses, a pulse on RING2 indicates the event. The
system logic must be able to discriminate a single
pulse of approximately 1 msec when using the
recommended external snoop circuit components
from a valid ringing signal.
3.2.3 On-hook Caller ID Signal Reception
On-hook Caller IDentity (CID) data burst signals are
coupled through the snoop components, buffered
through LITELINK and output at the RX+ and RX-
pins.
In North America, CID data signals are typically sent
between the first and second ringing signal while in
other countries the CID information may arrive prior to
any other signalling state.
In applications that transmit CID after the first ringing
burst such as in North American, follow these steps to
receive on-hook caller ID data via the LITELINK RX
outputs:
1. Detect the first full ringing signal burst on RING
or RING2.
2. Monitor and process the CID data from the RX
outputs.
For applications as in China and Brazil where CID may
arrive prior to ringing, follow these steps to receive
on-hook caller ID data via the LITELINK RX outputs:
1. Simultaneously monitor for CID data from the RX
outputs and for ringing on RING or RING2.
2. Process the appropriate signalling data.
Note: Taking LITELINK off-hook (via the OH pin)
disconnects the snoop path from the receive outputs
and disables the ringing detector outputs RING and
RING2.
CID gain from tip and ring to RX+ and RX- is
determined by:
R03
www.ixysic.com
11