ACS8509 Semtech Corporation, ACS8509 Datasheet - Page 8

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

The ACS8509 is a highly integrated, single-chip solution
for the SETS function in a SONET/SDH Network Element,
for the generation of SEC and frame synchronization
pulses.
In Free-run mode, the ACS8509 generates a stable, low
noise clock signal from an internal oscillator.
In Locked mode, the ACS8509 selects the most
appropriate input reference source and generates a
stable, low-noise clock signal locked to the selected
reference.
In Holdover mode, the ACS8509 generates a stable, low-
noise clock signal from the internal oscillator, adjusted to
match the last known good frequency of the last selected
reference source.
In all modes, the frequency accuracy, jitter and drift
performance of the clock meet the requirements of ITU
G.812
CORE
The ACS8509 supports all three types of reference clock
source: recovered line clock (T
synchronization timing (T
(T
T
a 2 kHz Multi-Frame Synchronization clock.
The ACS8509 has a high tolerance to input jitter and
wander. The jitter/wander transfer is programmable (0.1
Hz up to 20 Hz cut-off points).
The ACS8509 supports protection. Two ACS8509 devices
can be configured to provide protection against a single
ACS8509
The protection maintains alignment of the two ACS8509
devices (Master and Slave) and ensures that both
ACS8509 devices maintain the same priority table,
choose the same reference input and generate the T
clock, the 8 kHz Frame Synchronization clock and the 2
kHz Multi-Frame Synchronization clock with the same
phase.
The ACS8509 includes a microprocessor port, providing
access to the configuration and status registers for device
setup and monitoring.
Local Oscillator Clock
The Master system clock on the ACS8509 should be
provided by an external clock oscillator of frequency
Revision 2.00/January 2006 © Semtech Corp.
Functional Description
ADVANCED COMMUNICATIONS
OUT4
IN3
). The ACS8509 generates independent T
[19]
clocks, an 8 kHz Frame Synchronization clock and
[10]
failure.
.
, G.813
[11]
, G.823
IN2
) and node synchronization
[13]
IN1
, and Telcordia GR-1244-
), PDH network
OUT0
and
OUT0
FINAL
Page 8
12.80 MHz. The clock specification is important for
meeting the ITU/ETSI and Telcordia performance
requirements for Holdover mode. ITU and ETSI
specifications permit a combined drift characteristic, at
constant temperature, of all non-temperature related
parameters, of up to 10 ppb per day. The same
specifications allow a drift of 1 ppm over a temperature
range of 0 to +70°C.
Table 4 ITU and ETSI Specification
Telcordia specifications are somewhat tighter, requiring a
non-temperature-related drift of less than 40 ppb per day
and a drift of 280 ppb over the temperature range 0 to
+50°C.
Table 5 Telcordia GR-1244 CORE Specification
Please contact Semtech for information on crystal
oscillator suppliers.
Crystal Frequency Calibration
The absolute crystal frequency accuracy is less important
than the stability since any frequency offset can be
compensated by adjustment of register values in the IC.
This allows for calibration and compensation of any
crystal frequency variation away from its nominal value.
± 50 ppm adjustment would be sufficient to cope with
most crystals, in fact the range is an order of magnitude
larger due to the use of two 8-bit register locations. The
setting of the conf_nominal_frequency register allows for
this adjustment. An increase in the register value
increases the output frequencies by 0.02 ppm for each
LSB step. The default value (in decimal) is 39321.
Tolerance
Drift
(Frequency Drift
over supply
voltage range of
+2.7 V to +3.3 V)
Tolerance
Drift
(Frequency Drift
over supply
voltage range of
+2.7 V to +3.3 V)
Parameter
Parameter
±4.6 ppm over 20 year lifetime
±4.6 ppm over 20 year lifetime
±0.05 ppm/15 seconds @ constant temp.
±0.01 ppm/day @ constant temp.
±1 ppm over temp. range 0 to +70°C
±0.05 ppm/15 seconds @ constant temp.
±0.04 ppm/15 seconds @ constant temp.
±0.28 ppm/over temp. range 0 to +50°C
ACS8509 SETS
Value
Value
DATASHEET
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