CPC5621 datasheet(12/18 Pages) CLARE

12 / 18 page

CPC5620/CPC5621

www.clare.com

Rev. 0.E

rent. The photocurrent, a linear representation of the

receive signal, is amplified and converted to a differen-

tial voltage output on RX+ and RX-.

Variations in gain are controlled to within ±0.4 dB by

factory gain trim, which sets the output of the photo-

amplifier to unity gain.

To accommodate single-supply operation, 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.

Figure 6. Differential and Single-ended Receive

Path Connections to LITELINK

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

set to unity at the factory, limiting insertion loss to 0,

±0.4 dB.

Figure 7. Differential and Single-ended Transmit

Path Connections to LITELINK

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

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 RZDC (R16) and RDCS (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 RZDC (R16) using the following formula:

Clare recommends using 8.2

Ω for R

ZDC in North

America and Japan, limiting telephone line current to

133 mA.

RX+

RX-

RX+

RX-

0.1uF

LITELINK

Host-side CODEC

or Voice Circuit

LITELINK

TXA1

TXA2

0.1uf

Host CODEC or

Transmit Circuit

Host CODEC or

Transmit Circuit

TX-

TX+

TXA1

0.1uf

TX-

TX+

ICLAmps

RZDC

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

0.011A

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