CPC5620 Datasheet, PDF (12/18 Pages) Clare, Inc. – LITELINK III Phone Line Interface IC (DAA)

CPC5620/CPC5621
rent. The photocurrent, a linear representation of the
receive signal, is amplified and converted to a differen-
tial voltage output on RX+ and RX-.
set to unity at the factory, limiting insertion loss to 0,
±0.4 dB.
Variations in gain are controlled to within ±0.4 dB by
factory gain trim, which sets the output of the photo-
Figure 7. Differential and Single-ended Transmit
amplifier to unity gain.
Path Connections to LITELINK
To accommodate single-supply operation, LITELINK
Host CODEC or
Transmit Circuit
LITELINK
includes a small DC bias on the RX outputs of 1.0
Vdc. Most applications should AC couple the RX out-
puts as shown in Figure 6.
LITELINK may be used for differential or single-ended
output as shown in Figure 6. Single-ended use will
produce 6 dB less signal output amplitude. Do not
exceed 0 dBm into 600 Ω (2.2 V_P-P) signal input with
the standard application circuit. See application note
AN-149, Increased LITELINK II Transmit Power for more
information.
TXA1
TXA2
ry Host CODEC or
Transmit Circuit
ina ^TXA1
0.1uf TX-
-
0.1uf TX+
+
LITELINK
0.1uf _TX-
-
0.1uf _TX+
+
Figure 6. Differential and Single-ended Receive
Path Connections to LITELINK
lim ^{Host-side CODEC}
or Voice Circuit
LITELINK
RX+
e ^RX-
0.1uF
RX+
0.1uF
RX-
Pr ^RX
0.1uF
RX+
3.4 Start-up Requirements
OH must be de-asserted (set logic high) once after
power-up for at least 50 ms to transfer internal gain
trim values within LITELINK. This would be normal
operation in most applications.
3.5 DC Characteristics
3.3.2 Transmit Signal Path
Connect transmit signals from the host equipment to
the TX+ and TX- pins of LITELINK. Do not exceed a
signal level of 0 dBm in 600 Ω (or 2.2 V_P-P). Differen-
tial transmit signals are converted to single-ended sig-
nals in LITELINK. The signal is coupled to the transmit
photodiode amplifier in a similar manner to the receive
path.
The output of the photodiode amplifier is coupled to a
voltage-to-current converter via a transconductance
stage where the transmit signal modulates the tele-
phone line loop current. As in the receive path, gain is
The CPC5620 and CPC5621 are designed for world-
wide application regarding DC characteristics, includ-
ing use under the requirements of TBR-21. The ZDC,
DCS1, and DCS2 pins control the VI slope character-
istics of LITELINK. Selecting appropriate resistor val-
ues for R_ZDC (R16) and R_DCS (R15) in the provided
application circuits assure compliance with DC
requirements.
3.5.1 Non-Current Limited Applications
LITELINK includes a telephone line current limit fea-
ture that is selectable by selecting the desired value
for R_ZDC (R16) using the following formula:
I_CLAmps = -_R---¹_Z---^V_D----_C-- + 0.011A
Clare recommends using 8.2 Ω for R_ZDC in North
America and Japan, limiting telephone line current to
133 mA.
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Rev. 0.E