TS117S - Clare, Inc. - Datasheet.Directory

APPLICATION NOTE AN-113

TS117 Telecom Switch

www.clare.com

AN-113

Rev. 1

2-4 Wire

Conversion Surge

Protection

Off-Hook

Relay

Ring

Detect

Control

Unit

Modem RJ 11

Data

Jack

Figure 1. Typical Modem Circuit

TIP

RING

MOV

250V

10½

.68µF

250V

R Shunt

87 65

12 34

Pulse

Generator

VCC

DIAL

PULSE

COUPLING

TRANSFORMER

HOOKSWITCH

10k½

1k½

RINGING

SIGNAL

DETECTOR

TS117

4GND

RING

+5V

LOOP

CURRENT

DETECTION

Figure 2. Ring Detector and Loop Detector Circuit

SSRS FOR MODEMS

The use of relays in telecom circuits as a lng history. Originally, electromechanical relays were the only

vaible solution for these applicatoins. However, as modems, automatic telephone dialers, fax machines and

answering machinescontinue to expand in the data processing world, the need for state of the art technolo-

gy in the form of solid state relays (SSRs) has become apparent.

The SSR offers: High blocking Voltages, High Lod Currents, Low On-Resistance, Fast Switching speeds

and Input/Output Isolation of 3750 VRMS’ which make them an ideal solutoin for hookswitch, pulse dialing or

loop start switching operations.

Essentially, the modem begins in a standby or idle state in which t is disconnected from the telephone line

(See figrure 1). connection begins when a ring curretnais detected by the ring detection device (Clare: LDA

Series or “TS” Series). This device supplies a ring detection signal to the odem circuit which is used to ini-

tiate teh answer response mode. Once the ring detection signal is recognized and has initiate the answer

response mode. Once the ring detection signal is recognized and has initiated the answering sequence by

generating the ringing indication signal, the modem chip responds with a signal. the off hook signal gener-

ated by the modem is used to activate the hookswitch solid state relay (clare: LCA or PLA Series), closing

the circuit between th tip and ring wires and connecting the modem to the circuit.

Clare offers a wide range of SSRs for the telecom industry. Form A, B, C, single pole or dual pole devices,

detailed specifications of which ar found on pages 91282.

Figure 2 is a typical data access arrangement (DAA) design using Clare’s “TS” Series offers an ptically iso-

lated normally open (or normally closed) MOSFET based solid state relay, combined with a bi-directionally

driven photo-transistor, all in the same 8 pin DIP.

the Ring Detection portion of this circuit uses a capacitor (typical value .68µF) and a resistor (typical values

10K Ohms) in a series withe the bi-directional LEDs of the TS117, across the Tip and Ring lines of the cir-

cuit.

The resistor and capacitor values for the circuit must be chosen to provide sufficient curretn to operate the

detector portion of the TS117 at the riquired voltage of the ringer service. (For Class B ringer service volt-

age range of 40 to 150VRMS and frequency range of 15.3 to 68Hz.)

The impedance of this resistor/capacitor network is critical to the Ringer Equivalence Number (REN). the

smaller the impedance the larger the REN and if the REN is too large it will limit the number of telephone

devices that can be attached to the line.

The TS117 is sensitve to typical loop currents of 2mA alowiing the circuit designer the freedom to program

the actual in-circuit triggering current by appropriate choice of input shunt resistance.

AN-113

www.clare.com 3

Rev. 1

Clare’s Intergrated Telecom circuit (ITC117P) features combined circuitry in one 16 Pin SOIC package for:

•1-Form-A Solid State Relay for use as Hookswitch

•Bridge Rectifier

•Darlington Transistor

•Optocoupler that can function as a ring detector or loop current detector

Typical applications for the ITC117P include:

•PCMCIA Designs

•Modem

•Fax

•Voicemail Systems

•Telephone Sets

•Computer Telephony

DESCRIPTION

The ITC series integrates the major components found in a typical Data Access Arrangement (DAA), in a 16

lead SOIC package. As highlighted in figure 1, the 1-Form-A MOSFET SSR,Darlington transistor, bridge rec-

tifier, and optical isolator comprise this integral design. Following is the functional explanation for each

device:

Hookswitch

The ITC contains optically-coupled MOSFETs that function as a hookswitch in the DAA circuit. The hook-

switch has a blocking voltage up to 350V, isolation voltageto 3750VRMS, 15ΩRDS(on), and a maximum

switching current of 120mA, making it ideal for tip and ring switching. The hookswitch is controlled by an

LED that requires only 5mA to operate. This makes it an attractive device for battery-powered applicatoins

where power consumtion needs to be minimized for prolonged battery life.

Optocoupler

An optocoupler is included in the ITC series package that can be used as a ring detector or loop current

detector with the addition of a few passive components. the optocoupleris available with a standard photo-

transistor or a high gain Darlington transistor.

Bridge/Darlington

Referring to figure 2, a bridge rectifier (D2) and Darlington transistor (Q1) arrangement is inclded in the pack-

age for use in “dry” transformer and optical DAA designs. The bridge provides the function of current steer-

ingto maintain DAA operation and protect the Darlington during polarity reversals of a few passive

components, functions as an electronic iductor that has the effect of presenting a low resistance to the DC

curretn across the telephone line, and a relatively hig empedance for AC signals on the line. For a trans-

former based design, this enables the designer t use a small coupling transformer (T1) since the telephone

loop current is diverted through the Darlington instead passive components, functions as an electronic iduc-

tor that has the effect of presenting a low resistance to the DC curretn across the telephone line, and a rel-

atively hig empedance for AC signals on the line. For a transformer based design, this enables the designer

t use a small coupling transformer (T1) since the telephone loop current is diverted through the Darlington

instead of the transformer windings (“dry transformer”). Without the electronic inductor, the loop current

would have to flow through the transformer (“wet transformer”), however since the telehone loop current can

be as high as 120mA, the transformer would saturate, causing signal degradation unless the geopety of the

transformer becomes much larger. This is especially true for high speed modems such as V.34bis, where

return loss must meet or exceed 25dB. Return loss of 25dB is usually not attainable witha wet transformer,

and if it is, the transformer is too large and expensive for the application. *The best way to overcome this

sauration and return loss problem is to “rerout” the loop current through the electronic inductor and AC cou-

ple and modem signal via C2 to the transformer, such that no DC current flows through the transformer.

Return loss is a measure of mismatch

CLARE LOCATIONS

Clare Headquarters

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Tel: 1-978-524-6700

Fax: 1-978-524-4900

Toll Free: 1-800-27-CLARE

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145 Columbia

Aliso Viejo, CA 92656-1490

Tel: 1-949-831-4622

Fax: 1-949-831-4628

Clare Switch Division

4315 N. Earth City Expressway

Earth City, MO 63045

Tel: 1-314-770-1832

Fax: 1-314-770-1812

SALES OFFICES

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Tel: 1-905-333-9066

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EUROPE

European Headquarters

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Tel: 32-11-300868

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France

Clare France Sales

Lead Rep

99 route de Versailles

91160 Champlan

France

Tel: 33 1 69 79 93 50

Fax: 33 1 69 79 93 59

Germany

Clare Germany Sales

ActiveComp Electronic GmbH

Mitterstrasse 12

85077 Manching

Germany

Tel: 49 8459 3214 10

Fax: 49 8459 3214 29

Italy

C.L.A.R.E.s.a.s.

Via C. Colombo 10/A

I-20066 Melzo (Milano)

Tel: 39-02-95737160

Fax: 39-02-95738829

Sweden

Clare Sales

Comptronic AB

Box 167

S-16329 Spånga

Tel: 46-862-10370

Fax: 46-862-10371

United Kingdom

Clare UK Sales

Marco Polo House

Cook Way

Bindon Road

Taunton

UK-Somerset TA2 6BG

Tel: 44-1-823 352541

Fax: 44-1-823 352797

ASIA/PACIFIC

Asian Headquarters

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Room N1016, Chia-Hsin, Bldg II,

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Fax: 886-2-2523-6369

http://www.clare.com

Worldwide Sales Offices

Specification: AN-113-R1

OptoMOS®is a registered trademark of Clare, Inc.

6/25/01

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the accuracy or completeness of the contents of this publication

and reserves the right to make changes to specifications and

product descriptions at any time without notice. Neither circuit

patent licenses nor indemnity are expressed or implied. Except as

set forth in Clare’s Standard Terms and Conditions of Sale, Clare,

Inc. assumes no liability whatsoever, and disclaims any express or

implied warranty, relating to its products including, but not limit-

ed to, the implied warranty of merchantability, fitness for a partic-

ular purpose, or infringement of any intellectual property right.

The products described in this document are not designed,

intended, authorized or warranted for use as components in sys-

tems intended for surgical implant into the body, or in other appli-

cations intended to support or sustain life, or where malfunction

of Clare’s product may result in direct physical harm, injury, or

death to a person or severe property or environmental damage.

Clare, Inc. reserves the right to discontinue or make changes to its

products at any time without notice.