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參數(shù)資料
| 型號： | MT9044 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | T1/E1/OC3 System Synchronizer(T1/E1/OC3 系統(tǒng)同步裝置（由一個數(shù)字鎖相環(huán)組成）) |
| 中文描述： | T1/E1/OC3系統(tǒng)同步器（T1/E1/OC3系統(tǒng)同步裝置（由一個數(shù)字鎖相環(huán)組成）） |
| 文件頁數(shù)： | 16/34頁 |
| 文件大?。?/td> | 150K |
| 代理商： | MT9044 |
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MT9044
16
CTS CXO-65-HG-5-C-20.0MHz
Frequency:
Tolerance:
Rise & Fall Time:
Duty Cycle:
20MHz
25ppm 0C to 70C
8ns (0.5V 4.5V 50pF)
45% to 55%
The output clock should be connected directly (not
AC coupled) to the OSCi input of the MT9044, and
the OSCo output should be left open as shown in
Figure 9.
Crystal
Oscillator may be used. A complete oscillator circuit
made up of a crystal, resistor and capacitors is
shown in Figure 10.
Oscillator
-
Alternatively,
a
Crystal
Figure 10 - Crystal Oscillator Circuit
The accuracy of a crystal oscillator depends on the
crystal tolerance as well as the load capacitance
tolerance. Typically, for a 20MHz crystal specified
with a 32pF load capacitance, each 1pF change in
load capacitance contributes approximately 9ppm to
the frequency deviation. Consequently, capacitor
tolerances, and stray capacitances have a major
effect on the accuracy of the oscillator frequency.
The trimmer capacitor shown in Figure 10 may be
used
to
compensate
for
accuracy is not a concern, then the trimmer may be
removed, the 39pF capacitor may be increased to
56pF,
and
a
wider
tolerance
substituted.
capacitive
effects.
If
crystal
may
be
The crystal should be a fundamental mode type - not
an overtone. The fundamental mode crystal permits
a simpler oscillator circuit with no additional filter
components and is less likely to generate spurious
responses. The crystal specification is as follows.
Frequency:
Tolerance:
Oscillation Mode:
20MHz
As required
Fundamental
Resonance Mode:
Load Capacitance:
Maximum Series Resistance:
Approximate Drive Level:
e.g., CTS R1027-2BB-20.0MHZ
(
±
20ppm absolute,
±
6ppm 0C to 50C, 32pF, 25
)
Parallel
32pF
35
1mW
Guard Time Adjustment
Excessive switching of the timing reference (from
PRI to SEC) in the MT9044 can be minimized by first
entering
Holdover
Mode
maximum time (i.e., guard time). If the degraded
signal returns to normal before the expiry of the
guard time (e.g. 2.5 seconds), then the MT9044 is
returned to its Normal Mode (with no reference
switch taking place). Otherwise, the reference input
may be changed from Primary to Secondary.
for
a
predetermined
Figure 11 - Symmetrical Guard Time Circuit
A simple way to control the guard time (using
Automatic Control) is with an RC circuit as shown in
Figure 11. Resistor R
P
is for protection only and
limits the current flowing into the GTi pin during
power down conditions. The guard time can be
calculated as follows.
V
SIH
is the logic high going threshold level for the GTi
Schmitt Trigger input, see DC Electrical
Characteristics
In cases where fast toggling might be expected of
the LOS1 input, then an unsymmetrical Guard Time
Circuit is recommended. This ensures that reference
switching doesn’t occur until the full guard time value
OSCo
56pF
1M
39pF
3-50pF
20MHz
MT9044
OSCi
100
1uH
1uH inductor: may improve stability and is optional
GTi
C
10uF
R
150k
MT9044
GTo
+
R
P
1k
guardtime
RC
–
VDD
VSIH
---------------------------------
ln
×
=
guardtime
RC
0.6
×
≈
guardtime
150
k
10
u
×
0.6
0.9
s
=
×
≈
example
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| MT9044AL | 制造商:Microsemi Corporation 功能描述:FRAMER E1/OC3/T1 5V 44MQFP - Trays 制造商:Zarlink Semiconductor Inc 功能描述:FRAMER E1/OC3/T1 5V 44MQFP - Trays |
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| MT9044APR1 | 制造商:Microsemi Corporation 功能描述:FRAMER E1/OC3/T1 5V 44PLCC - Tape and Reel 制造商:Zarlink Semiconductor Inc 功能描述:FRAMER E1/OC3/T1 5V 44PLCC - Tape and Reel |
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