MH89101 datasheet(3/4 Pages) MITEL

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Advance Information

MH89101

Functional Description

The termination network is an all passive circuit

which allows the DSLIC to interface to the DSL

through a pulse transformer. The equivalent circuit

of the Passive

Line Termination Network can be

seen in Figure 3 below.

The PLT consists of two blocks which includes a

hybrid network and a compensator circuit.

The hybrid network is a 2 to 4 wire converter which

provides a large degree of precancellation of the

near end signal while presenting little attenuation to

the far end signal.

This is performed using a

summing junction which effectively subtracts the

transmit signal from the receive path.

The compensator circuit, in conjunction with the

transformer, acts as a highpass filter reducing the

low frequency content in the received line signal.

This, in turn, decreases the effects of ISI and near

end echo, and improves the transceiver perfor-

mance.

Typical Application

Figure 4 shows a typical connection diagram of the

MT8910 DSLIC and the Passive Line Termination

Circuit. As seen in Figure 4, the PLT is positioned

between the DSLIC and the line pulse transformer.

Two series protection resistors on the secondary of

the line pulse transformer are used to dissipate any

extraneous energy which may be induced onto the

transmission line.

Figure 3 - Passive Line Termination Network

TXIN +

RXOUT +

RXOUT -

TXIN -

680 pF

130 K

Ω

68K2

Ω

130 K

Ω

680 pF

3.3 nF

20 K

Ω

7K8

Ω

20 K

Ω

3.3 nF

Rs = 30.2 Ω

Rb1

1K6

Ω

Rb1

1K6

Ω

Rs = 30.2 Ω

Rb2

Ω

Rb2

Ω

XFM +

XFM -

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