ACS8509 Semtech Corporation, ACS8509 Datasheet - Page 11

• Manufacturer Part Number: ACS8509
• Description: Synchronous Equipment Timing Source for Sonet or SDH Network Elements
• Manufacturer: Semtech Corporation

the frequency outside the hold-in range for long enough to
be detected, whilst the signal will also be rejected if the
eye closes sufficiently to affect the signal purity). The
“8klock” mode should be engaged for high jitter tolerance
according to these masks. All reference clock ports are
monitored for quality, including frequency offset and
general activity. Single short-term interruptions in
selected reference clocks may not cause
rearrangements, whilst longer interruptions, or multiple,
short-term interruptions, will cause rearrangements, as
will frequency offsets which are sufficiently large or
sufficiently long to cause loss-of-lock in the phase-locked
loop. The failed reference source will be removed from the
priority table and declared as unserviceable, until its
perceived quality has been restored to an acceptable
level.
Table 7 Input Reference Source Jitter Tolerance
Notes: (i) The frequency acceptance and generation range will be ±4.6 ppm around the required frequency when the external crystal
Revision 2.00/January 2006 © Semtech Corp.
ADVANCED COMMUNICATIONS
G.703
G.783
G.823
GR-1244-CORE
Jitter Tolerance
(ii) The fundamental acceptance range and generation range is ± 9.2 ppm with an exact external crystal frequency of 12.8 MHz. This is
frequency accuracy is within a tolerance of ±4.6 ppm.
the default DPLL range, the range is also programmable from 0 to 80 ppm in 0.08 ppm steps.
Frequency Monitor
Acceptance Range
±16.6 ppm
Frequency Acceptance
Range (Pull-in)
(see Note (ii))
(see Note (i))
FINAL
±4.6 ppm
±9.2 ppm
Page 11
The registers sts_curr_inc_offset (address 0C, 0D, 07)
report the frequency of the DPLL with respect to the
external TCXO frequency. This is a 19-bit signed number
with one LSB representing 0.0003 ppm (range of
±80 ppm). Reading this regularly can show how the
currently locked source is varying in value e.g. due to
wander on its input.
The ACS8509 performs automatic frequency monitoring
with an acceptable input frequency offset range of
±16.6 ppm. The
frequency limit of ±80 ppm. If the range is programmed to
be > 16.6 ppm, the frequency monitors should be
disabled so the input reference source is not
automatically rejected as out of frequency range.
Frequency Acceptance
Range (Hold-in)
ACS8509
(see Note (ii))
(see Note (i))
±4.6 ppm
±9.2 ppm
DPLL has a programmable
ACS8509 SETS
Frequency Acceptance
Range (Pull-out)
(see Note (ii))
(see Note (i))
DATASHEET
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±4.6 ppm
±9.2 ppm