MT9075B datasheet(8/78 Pages) MITEL

8 / 78 page

MT9075B

Preliminary Information

Functional Description

MT9075B Line Interface Unit (LIU)

Receiver

The receiver portion of the MT9075B LIU consists of

an input signal peak detector, an optional two-stage

equalizer, a smoothing ﬁlter, adaptive threshold

comparators, data and clock slicers, and a clock

extractor. Receive equalization gain can be set via

software

control

can

determined

automatically by the peak detectors.

The output of the receive equalizer is conditioned by

a smoothing ﬁlter and is passed on to the clock and

data slicer. The clock slicer output signal drives a

phase locked loop, which generates the extracted

clock (E2o). This extracted clock is used to sample

the output of the data comparator.

The LOS output pin (pin 61 in PLCC, pin 57 in

MQFP) is user selectable, by setting control bit LOS/

LOF (page 02H, register 13H, bit 2), to indicate a

loss of signal or loss of basic frame synchronization

condition. In addition, a status bit, LLOS (bit 4 in

page 3, register 18H) is provided to indicate the

presence of a loss signal condition. The occurrence

of a loss signal condition is deﬁned as per I.431, i.e.,

when the incoming signal amplitude is more than 20

dB below the nominal amplitude for a time duration

of at least 1 ms.

The receive LIU circuit requires a terminating

resistor of either 120

Ω or 75Ω across the device side

of the receive1:1 transformer as shown in Figure 4.

The return loss of the receiver, complying with

G.703, is greater than:

•

12 dB from 51 kHz to 102 kHz;

•

18 dB from 102 kHz to 2048 kHz;

•

14 dB from 2048 kHz to 3072 kHz.

The jitter tolerance of the MT9075B clock extractor

circuit exceeds the requirements of G.823 (Figure 3).

Transmitter

The MT9075B differential line driver is designed to

drive a 1:2 step-up transformer (see Figure 4). A

0.68 uF capacitor is required between the TTIP and

the transmit transformer. Resistors RT (as shown in

Figure 4) are for termination for transmit return loss.

The values of RT may be optimized for 120Ω lines,

Ω lines or set at an intermediary value to serve

both applications. Program the Transmit Pulse

Control Word (address 1FH page 1) to adjust the

pulse amplitude accordingly. Alternatively, the pulse

level and shape may be discretely programmed by

writing to the Customer Pulse Level registers

(addresses 1CH to 1FH, page 2) and setting the

Custom Transmit Pulse bit high (bit 3 of the Transmit

Pulse Control Word).

Figure 3 - Typical Jitter Tolerance

18UI

1.5UI

0.2UI

1.667Hz

20Hz

2.4kHz 18kHz 100kHz

Peak to Peak

Jitter Amplitude

(log scale)

Jitter Frequency

(log scale)

MT9075B

Tolerance

MT9075B Datenblatt(PDF) 8 Page - Mitel Networks Corporation

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