Preliminary Information

MH88435-P

2-41

18,

19

NP

No Pin. Isolation barrier, no pin fitted in this position.

21,

22

SC

Short Circuit. These two pins should be connected to each other via a 0

Ω

link.

24

VLOOP2

Loop Voltage Control Node 2. Used to set DC termination characteristics.

25

VLOOP1

Loop Voltage Control Node 1. Used to set DC termination characteristics.

27

RING

Ring Lead. Connects to the “Ring” lead of the telephone line.

28

TIP

Tip Lead. Connects to the “Tip” lead of the telephone line.

Pin Description (continued)

Functional Description

The device is a Data Access Arrangement (D.A.A.). It

is used to correctly terminate a 2-Wire telephone

line. It provides a signalling link and a 2-4 Wire line

interface between an analog loop and subscriber

data transmission equipment, such as Modems,

Facsimiles (Fax’s), Remote Meters, Electronic Point

of Sale equipment and Set Top Boxes.

Isolation Barrier

The device provides an isolation barrier capable of

meeting the supplementary barrier requirements of

the international standard IEC 950 and the national

variants of this scheme such as EN 60950 for

European applications and UL 1950 for North

American applications and is classified as a Telecom

Network Voltage (TNV) circuit.

External Protection Circuit

An External Protection Circuit assists in preventing

damage to the device and the subscriber equipment,

due to over-voltage conditions. See Application Note,

MSAN-154 for recommendations.

Suitable Markets

The MH88435 has features such as programmable

input

and

network

balance

impedance,

programmable DC termination and a supplementary

isolation

barrier

that

makes

it

ideal

for

use

throughout the world.

There are a small number of countries with a 100M

Ω

leakage requirement that this device does not meet.

These are Belgium, Greece, Italy, Luxembourg and

Spain.

France’s current limit specification and Germany’s

dial pulse requirements are met by the MH88437.

This device is pin for pin compatible with the

MH88435.

Approval specifications are regularly changing and

the relevant specification should always be consulted

before commencing design.

Line Termination

When Loop Control (LC) is at a logic 1, a line

termination is applied across Tip and Ring. The

device is off-hook and DC loop current will flow. The

line

termination

consists

of

both

a

DC

line

termination and an AC input impedance. It is used to

terminate an incoming call, seize the line for an

outgoing call, or if it is applied and disconnected at

the required rate, can be used to generate dial

pulses.

The

DC

termination

is

approximately

300

Ω

resistance, which is loop current dependent. It can

be

programmed

to

meet

different

national

requirements. For normal operation Pin 22 and Pin

21 should be linked, and a resistor (R2) should be

fitted between VLOOP1 and VLOOP2 as shown in

Figure 5.

The approval specification will give a DC mask

characteristic that the equipment will need to comply

to. The DC mask specifies the amount of current the

DAA can source for a given voltage across tip and

ring. Figure 3 shows how the voltage across tip and

ring varies with different resistors (R2) for a given

loop current.

The AC input impedance should be set by the user to

match the line impedance.