CPC5610/CPC5611

Rev. 9.0

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13

3.5 AC Characteristics

3.5.1 Resistive Termination Applications

North American and Japanese telephone line AC ter-

mination 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, R

ZNT

(R10). A 150

Ω resistor, R18 (R

LITELINK ZTX pin (pin 30) sets the correct transmit

gain and impedance.

3.5.2 Reactive Termination Applications

Many areas use a single-pole complex impedance to

model the telephone network transmission line char-

acteristic impedance as shown in the table below.

Matching a complex impedance requires the use of

complex networks on ZNT and ZTX. In order to

accommodate high power levels, it is necessary to

modify the transmit and receive gain characteristics of

your LITELINK implementation. The complex network

on the ZTX pin increases transmit gain by 7 dB. A 7

dB pad may be inserted before the TX+ and TX- pins

to provide overall unity gain. Similarly, with a complex

be modified from 1:1 to 1:.287, which introduces a 7

dB loss in the receive path from tip and ring to ZNT.

4. Regulatory Information

LITELINK 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 com-

plies with the requirements of UL1577. LITELINK pro-

vides supplementary isolation. Metallic surge

requirements are met through the inclusion of a Sidac-

tor in the application circuit. Longitudinal surge protec-

tion is provided by LITELINK’s optical-across-the-

barrier technology and the use of high-voltage compo-

nents 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 compli-

ance. Since it is the equipment manufacturer's respon-

sibility 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 result-

ing from inadequate protection measures at the board

or system level.

Line Impedance Model

TBR-21

Australian

Ra

750

820

Rb

270

220

C

150 nF

120 nF