ACS8509T View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'ACS8509T' PDF : 68 Pages View PDF
ADVANCED COMMUNICATIONS
FINAL
Figure 5 Sample of Wander and Jitter Measured Transfer Characteristics
ACS8509 SETS
DATASHEET
F8530D_005WANJITTXFR_04bitmap.bmp
The required performance for phase variation during
Holdover is specified in several ways depending upon the
particular circumstances pertaining:
1. ETSI 300 462-5, Section 9.1, requires that the short
term phase error during switchover (i.e., Locked to
Holdover to Locked) be limited to an accumulation
rate no greater than 0.05 ppm during a 15 second
interval.
slips (of 125 µs each) occur during the first day of
Holdover. This requires a frequency accuracy better
than:
((24x60x60)+(255x125µs))/(24x60x60) = 0.37 ppm
Temperature variation is not restricted, except to
within the normal bounds of 0 to 50 °C.
2. ETSI 300 462-5, Section 9.2, requires that the long
term phase error in the Holdover mode should not
exceed:
{(a1+a2)S+0.5bS2+c} where:
a1 = 50 ns/s (allowance for initial frequency offset)
4. Telcordia GR.1244.CORE, Section 5.2., Table 4,
shows that an initial frequency offset of 50 ppb is
permitted on entering Holdover, whilst a drift over
temperature of 280 ppb is allowed; an allowance of
40 ppb is permitted for all other effects.
a2 = 2000 ns/s (allowance for temperature variation)
b = 1.16 x 10-4 ns/s2 (allowance for ageing)
c = 120 ns (allowance for entry into Holdover mode).
3. ANSI Tin1.101-1994, Section 8.2.2, requires that the
phase variation be limited so that no more than 255
5. ITU G.822, Section 2.6, requires that the slip rate
during category (b) operation (interpreted as being
applicable to Holdover mode operation) be limited to
less than 30 slips (of 125 µs each) per hour:
((((60 x 60)/30)+125µs)/(60x60)) = 1.042 ppm
Revision 2.00/January 2006 © Semtech Corp.
Page 15
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