ACS8510REV2.1 Semtech Corporation, ACS8510REV2.1 Datasheet - Page 18

• Manufacturer Part Number: ACS8510REV2.1
• Description: Synchronous Equipment Timing Source for Sonet or SDH Network Elements
• Manufacturer: Semtech Corporation

Table 9. Multiple E1/DS1 Ouputs in relation to Standard Outputs
Table 9. Multiple E1/DS1 Ouputs in relation to Standard Outputs
Table 9. Multiple E1/DS1 Ouputs in relation to Standard Outputs
Table 9. Multiple E1/DS1 Ouputs in relation to Standard Outputs
Table 9. Multiple E1/DS1 Ouputs in relation to Standard Outputs
the filter can be opened up to reduce locking
time and can then be gradually tightened again
to remove wander. Since wander represents a
relatively long-term deviation from the nominal
operating frequency, it affects the rate of supply
of data to the network element. Strong wander
attenuation limits the rate of consumption of
data to within a smaller range, so a larger buffer
store is required to prevent data loss. But, since
any buffer store potentially increases latency,
wander may often only need to be removed at
specific points within a network where buffer
stores are acceptable, such as at digital cross
connects. Otherwise, wander is sometimes not
required to be attenuated and can be passed
through transparently. The ACS8510 has
programmable wander transfer characteristics
in a range from 0.1 Hz to 20 Hz. The wander
and jitter transfer characteristic is shown in
Figure 5.
Wander on the local oscillator clock will not
have significant effect on the output clock whilst
in Locked mode, so long as the DPLL bandwidth
is set high enough so that the DPLL can
compensate quickly enough for any frequency
changes in the crystal. In Free-run or Holdover
mode wander on the crystal is more significant.
Revision 2.00/September 2003
ADVANCED COMMUNICATIONS
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Variation in crystal temperature or supply
voltage both cause drifts in operating frequency,
as does ageing. These effects must be limited
by careful selection of a suitable component
for the local oscillator, as specified in the section
‘Local Oscillator Clock’.
Phase Variation
Phase Variation
Phase Variation
Phase Variation
Phase Variation
There will be a phase shift across the ACS8510
between the selected input reference source
and the output clock. This phase shift may vary
over time but will be constrained to lie within
specified limits. The phase shift is characterised
using two parameters, MTIE (Maximum Time
Interval Error), and TDEV (Time Deviation), which,
although being specified in all relevent
specifications, differ in acceptable limits in each
one. Typical measurements for the ACS8510
are shown in Figures 6 and 7, for Locked mode
operation.
measurement of Phase Error accumulation in
Holdover mode operation.
The required performance for phase variation
during Holdover is specified in several ways
depending upon the particular circumstances
pertaining:
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ACS8510 Rev2.1 SETS
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