PT7A4401C Datasheet, PDF (8/27 Pages) List of Unclassifed Manufacturers – PT7A4401C T1/E1 System Synchronizer

Data Sheet
PT7A4401C T1/E1 System Synchronizer
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Applications Information
Master Clock
The PT7A4401C uses either an external clock source or an
external crystal and a few passive components with its internal
oscillator as the master timing source.
When selecting the clock oscillator, following specifications
should be considered. They are
- absolute frequency
- frequency change over temperature
- output rise and fall time
- output level
- duty cycle
In Free-Run State, the frequency tolerance of the PT7A4401C
output clocks are equal to the frequency tolerance of the tim-
ing source. In a given application, if an accurate Free-Run
State is not required, the tolerance of the master timing source
may be 100ppm. If required, the tolerance must be no worse
than 32 ppm.
The capture range of PT7A4401C must also be considered
when deciding the accuracy of the master timing source. The
sum of the accuracy of the master timing source and the cap-
ture range of the PT7A4401C will always equal 230ppm. For
example, if the master timing source is 100ppm, the capture
range will be 130ppm.
• Crystal Oscillator
If a crystal and passive components operating together with
the PT7A4401C oscillator are selected as the master timing
source, they should be connected as shown in Figure 4. It
should be possible to adjust the trimmer capacitor so that the
frequency is well within the 32 ppm tolerance; however, only
the proper specification of components will insure this toler-
ance over the necessary temperature range.
Figure 4. Crystal Oscillator Connection
• Clock Oscillator
If using an external clock source, its output pin should be
connected directly (not AC coupled) to the OSCi pin of the
PT7A4401C, and the OSCo pin can be left open as shown in
Figure 3 or connected as an output pin.
PT7A4401C
OSCi
1MΩ
20MHz
56pF
39pF 3-50pF
Figure 3. Clock Oscillator Connection
PT7A4401C
+5V
OSCi
+5V
20MHz OUT
GND
OSCo
No Connection
OSCo
100Ω
0.1µF
The crystal specification is as follows:
- Frequency:
- Tolerance:
- Oscillation Mode:
- Resonance Mode:
- Load Capacitance:
- Maximum Series Resistance:
- Αpproximate Drive Level:
20MHz
as required
Fundamental
Parallel
32pF
35Ω
1mW
PT0108(09/02)
8
Ver:0