Preliminary Information
MT9075B
Tx
Manufacturer
Filtran
Pulse Engineering
For Tx
5721-1
PE-65351
50027
For Rx
5721-2
PE-64934
50026
0.68uF
TTIP
TRING
R
T
1:2
Midcom
R
T
* 2.4
Ω
resistors are only
required with 75
Ω
coax
MT9075B
OSEC
02934/A
02935/A
Table 1 - Transformer Manufacturers and Part
Numbers
Timing Source
The MT9075B 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
MT9075B.
+
5V
MT9075B
1:1
RTIP
RRING
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.
OSC1
20MHz
OUT
Vdd
Percentage of
Nominal Peak
120
110
100
90
80
GND
269nS
244nS
194nS
OSC2
.1µF
(
open
)
50
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.
Nominal Pulse
219nS
488nS
10
0
-10
-20
Figure 5 - Pulse Template (G.703)
Frequency:
Tolerance:
Oscillation Mode:
Resonance Mode:
Load Capacitance:
Maximum Series Resistance:
Approximate Drive Level:
20MHz
50ppm
Fundamental
Parallel
32pF
35
Ω
1mW
Transformer Recommendation
Table 1 shows a list of recommended transformers
for the MT9075B line interface.
9
MITEL [ MITEL NETWORKS CORPORATION ]
