CPC5622 Clare, CPC5622 Datasheet - Page 12

• Manufacturer Part Number: CPC5622
• Description: LITELINK III, Full-wave Ring Detect
• Manufacturer: Clare

CPC5622
The recommended components in the application
circuits yield a gain 0.26 dB at 2000 Hz. Clare
Application Note AN-117
Ring Detect Voltage Threshold
different component values in this circuit. Changing
the CID gain will also change the ringing 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
1.8MΩ 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 then
converted to infrared light by the receive path LED.
The intensity of the light is modulated by the receive
signal and coupled across the electrical isolation
barrier to the SELV side photodiode.
On the host equipment (low voltage) side of the
barrier, the receive signal is converted by a
photodiode into photocurrent. The photocurrent, a
linear representation of the receive signal, is amplified
and converted to a differential voltage output on RX+
and RX-.
Variations in gain are controlled to within ±0.4 dB by
factory gain trim.
To accommodate single-supply operation, LITELINK
includes a small DC bias on the RX+ and RX- outputs
of 1.0 Vdc. Most applications should AC couple the
receive outputs as shown in Figure 5.
LITELINK may be used for differential or single-ended
output as shown in Figure 5. Single-ended use will
produce 6 dB less signal output amplitude. Do not
exceed 0 dBm referenced to 600 Ω (2.2 V
output level with the standard application circuits. See
12
Customize Caller ID Gain and
is a spreadsheet for trying
P-P
) signal
www.clare.com
application note AN-157,
Power
Figure 5. Differential and Single-ended Receive
3.3.2 Transmit Signal Path
Transmit signals from the CODEC to the TX+ and TX-
pins of LITELINK should be coupled through
capacitors as shown in Figure 6 to minimize dc offset
errors. Differential transmit signals are converted to
single-ended signals within LITELINK then coupled to
the optical transmit amplifier in a manner similar to the
receive path.
The output of the optical amplifier is coupled to a
voltage-to-current converter via a transconductance
stage where the transmit signal modulates the
telephone line loop current. As in the receive path, the
transmit gain is calibrated at the factory, limiting
insertion loss to 0 ±0.4 dB.
Differential and single-ended transmit signals into
LITELINK should not exceed a signal level of 0 dBm
referenced to 600 Ω (or 2.2 V
levels above 0dBm consult the application note
AN-157,
information.
Host-side CODEC
or Voice Circuit
for more information.
Increased LITELINK III Transmit Power
Path Connections to LITELINK
RX+
RX
RX-
0.1uF
0.1uF
0.1uF
Increased LITELINK III Transmit
P-P
). For output power
LITELINK
RX+
RX+
RX-
for more
Rev. 1.0