CPC5621 datasheet(13/17 Pages) CLARE

13 / 17 page

CPC5620/CPC5621

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3.5.1 Setting a Current Limit

LITELINK includes a telephone line current limit

feature that is selectable by choosing the desired

value for RZDC (R16) using the following formula:

Clare recommends using 8.2

Ω for R

ZDC for most

applications, limiting telephone line current to 130 mA.

Whether using the recommended value above or

when setting RZDC higher for a lower loop current limit

refer to the guidelines for FET thermal management

provided in AN-146, Guidelines for Effective

LITELINK Designs.

3.6 AC Characteristics

3.6.1 Resistive Termination Applications

North American and Japanese telephone line AC

termination requirements are met with a resistive 600

Ω AC termination. Receive termination is applied to

the LITELINK ZNT pin (pin 29) as a 301

Ω resistor,

RZNT (R10).

3.6.2 Reactive Termination Applications

Many countries use a single-pole complex impedance

to model the telephone network transmission line

characteristic impedance as shown in the table below.

Proper gain and termination impedance circuits for a

complex impedance requires the use of complex

network on ZNT as shown in the “Reactive Termination

Application Circuit Schematic” on page 8.

3.6.3 Mode Pin Usage

Assert the MODE pin low to introduce a 7 dB pad into

the transmit path and add 7 dB of gain to the receive

path. These changes compensate for the gain

changes made to the transmit and receive paths in

reactive termination implementations.

Insertion loss with MODE de-asserted and the

resistive termination application circuit is 0 dB.

Insertion loss with the reactive termination application

circuit and MODE asserted is also 0 dB.

4. Regulatory Information

LITELINK III can be used to build products that comply

with the requirements of TIA/EIA/IS-968 (formerly

FCC part 68), FCC part 15B, TBR-21, EN60950,

UL1950, EN55022B, IEC950/IEC60950, CISPR22B,

EN55024, and many other standards. LITELINK

provides supplementary isolation. Metallic surge

requirements are met through the inclusion of a

Sidactor in the application circuit. Longitudinal surge

protection is provided by LITELINK’s optical barrier

technology and the use of high-voltage components in

the application circuit as needed.

The information provided in this document is intended

to inform the equipment designer but it is not sufficient

to assure proper system design or regulatory

compliance. Since it is the equipment manufacturer's

responsibility to have their equipment properly

designed to conform to all relevant regulations,

designers using LITELINK are advised to carefully

verify that their end-product design complies with all

applicable safety, EMC, and other relevant standards

and regulations. Semiconductor components are not

rated to withstand electrical overstress or electro-static

discharges resulting from inadequate protection

measures at the board or system level.

5. LITELINK Design Resources

The Clare, Inc. web site has a wealth of information

useful for designing with LITELINK, including

application notes and reference designs that already

meet all applicable regulatory requirements. See the

following links:

LITELINK datasheets and reference designs

Application note AN-117 Customize Caller ID Gain

and Ring Detect Voltage Threshold

Application note AN-146, Guidelines for Effective

LITELINK Designs

Application note AN-152 LITELINK II to LITELINK III

Design Conversion

Application note AN-155 Understanding LITELINK

Display Feature Signal Routing and Applications

Line Impedance Model

Australia

China

TBR 21

220

200

270

820

680

750

120 nF

100 nF

150 nF

ICLAmps

RZDC

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