MT9075A Просмотр технического описания (PDF) - Mitel Networks

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MT9075A

E1 Single Chip Transceiver

Mitel Networks 

Preliminary Information

MT9075A

Tx

TTIP

0.68uF 2.4Ω* 1:2

TRING

MT9075A

2.4Ω*

* 2.4 Ω resistors are only

required with 75 Ω coax

RTIP

RRING

1:1

120Ω/

75Ω

Rx

Figure 4 - Analog Line Interface

The template for the transmitted pulse, as specified in

G703, is shown in Figure 5. The nominal peak voltage

of a mark is 3 volts for 120 Ω twisted pair applications

and 2.37 volts for 75 Ω coax applications. The ratio of

the amplitude of the transmit pulses generated by TTP

and TRING is between 0.95 and 1.05.

Percentage of

Nominal Peak

120

110

100

90

80

50

269nS

244nS

194nS

10

0

-10

Nominal Pulse

-20

219nS

488nS

Figure 5 - Pulse Template (G.703)

Transformer Recommendation

Manufacturer

For Tx

For Rx

Filtran

5721-1

5721-2

Pulse Engineering PE-65351 PE-64934

Midcom

50027

50026

OSEC

02934/A

02935/A

Table 1 - Transformer Manufacturers and Part

Numbers

Timing Source

The MT9075A can use either a clock or crystal,

connecting to pins OSC1 and OSC2, as the

reference timing source.

Figure 6 shows a 20MHz clock oscillator, with 50ppm

tolerance, directly connected to the OSC1 pin of the

MT9075A.

MT9075A

OSC1

+5V

20MHz

OUT

Vdd

GND

.1µF

OSC2

(open)

Figure 6 - Clock Oscillator Circuit

Alternatively, a crystal oscillator may be used. A

complete oscillator circuit made up of a crystal,

resistors and capacitors is shown in Figure 7. The

crystal specification is as follows.

Frequency:

Tolerance:

Oscillation Mode:

Resonance Mode:

Load Capacitance:

Maximum Series Resistance:

Approximate Drive Level:

20MHz

50ppm

Fundamental

Parallel

32pF

35Ω

1mW

Table 1 shows a list of recommended transformers

for the MT9075A line interface.

4-137

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