ACS8510 Semtech, ACS8510 Datasheet - Page 40

• Manufacturer Part Number: ACS8510
• Manufacturer: Semtech

Specifications of ACS8510

• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (max): 3.6/5.5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Package Type: LQFP
• Mounting: Surface Mount
• Pin Count: 100
• Lead Free Status / Rohs Status: Not Compliant

Activity Monitoring
Activity Monitoring
Occasional anomalies do not cause the
accumulator to cross the alarm setting
threshold, so the selected reference source is
retained. Persistent anomalies cause the alarm
setting threshold to be crossed and result in
the selected reference source being rejected.
Activity Monitoring
Activity Monitoring
Activity Monitoring
The ACS8510 has a combined inactivity and
irregularity monitor. The ACS8510 uses a ‘leaky
bucket’ accumulator, which is a digital circuit
which mimics the operation of an analog
integrator, in which input pulses increase the
output amplitude but die away over time. Such
integrators are used when alarms have to be
triggered either by fairly regular defect events,
which occur sufficiently close together, or by
defect events which occur in bursts. Events
which are sufficiently spread out should not
trigger the alarm. By adjusting the alarm setting
threshold, the point at which the alarm is
triggered can be controlled. The point at which
the alarm is cleared depends upon the decay
rate and the alarm clearing threshold. On the
alarm setting side, if several events occur close
together, each event adds to the amplitude
and the alarm will be triggered quickly; if events
occur a little more spread out, but still
sufficiently close together to overcome the
decay, the alarm will be triggered eventually. If
events occur at a rate which is not sufficient to
overcome the decay, the alarm will not be
triggered. On the alarm clearing side, if no defect
events occur for a sufficient time, the amplitude
will decay gradually and the alarm will be cleared
when the amplitude falls below the alarm
clearing threshold. The ability to decay the
amplitude over time allows the importance of
defect events to be reduced as time passes
by. This means that, in the case of isolated
events, the alarm will not be set, whereas, once
the alarm becomes set, it will be held on until
normal operation has persisted for a suitable
time (but if the operation is still erratic, the
alarm will remain set). See Figure 9.
Revision 2.00/September 2003
ADVANCED COMMUNICATIONS
Semtech Corp.
40
The
programmable for size, alarm set & reset
thresholds and decay rate.
monitored over a 128 ms period. If, within a
128 ms period, an irregularity occurs that is
not deemed to be due to allowable jitter/wander,
then the accumulator is incremented. The
accumulator will continue to increment up to
the point that it reaches the programmed
bucket size. The ‘fill rate’ of the leaky bucket
is, therefore, 8 units/second. The ‘leak rate’
of the leaky bucket is programmable to be in
multiples of the fill rate (x1, x0.5, x0.25 and
x0.125) to give a programmable leak rate from
8 units/sec down to 1 unit/sec.
between trying to ‘leak’ at the same time as a
‘fill’ is avoided by preventing a ‘leak’ when a
‘fill’ event occurs.
Disqualification of a non-selected reference
source is based on inactivity, or on an out of
band result from the frequency monitors. The
currently selected reference source can be
disqualified for phase, frequency, inactivity or if
the source is outside the DPLL lock range. If
the currently selected reference source is
disqualified, the next highest priority, active
reference source is selected.
Frequency Monitoring
Frequency Monitoring
Frequency Monitoring
Frequency Monitoring
Frequency Monitoring
The ACS8510 performs frequency monitoring
to identify reference sources which have drifted
outside the acceptable frequency range of
+/- 16.6 ppm (measured with respect to the
output clock). The sts_reference_sources out-
of-band alarm for a particular reference source
is raised when the reference source is outside
the acceptable frequency range. The ACS8510
DPLL has a programmable 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.
ACS8510 Rev2.1 SETS
‘leaky
bucket’
accumulators
Each source is
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