ACS9550EVB【PDF 1/4 页】EVALUATION BOARD FOR ACS9550

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ToPSync?

Timing-over-packet synchronization

ACS9550T

ADVANCED COMMS & SENSING

About the ToPSync? ACS9550T

The ToPSync? ACS9550T ASSP utilizes Semtech's ToPSync?

technology which, in conjunction with an appropriate Precision

Time Protocol (PTP) Grandmaster, can be used for many

applications which require a reference frequency that is

traceable to a remote, centralized, frequency source, or a time

or phase reference that is aligned to a central reference point

of phase or time.

Whilst the distribution of a common frequency reference has

been a key technology in most telecom networks since the

beginning of digital networks, the techniques used do not work

on packet switched networks. A new technique is required,

and the ACS9550T has been developed using a combination

of PTP and adaptive packet delay filtering. Although PTP was

conceived to use on-path support such as boundary clocks or

transparent clocks, the packet delay filtering of the ACS9550T

renders such support unnecessary.

As an example, if WiBro/WiMax transmitter stations do not

have a common phase across the regions in which they

overlap, interslot interference can occur. For this application, it

is not enough to distribute a frequency reference since the

individual path delays to each transmitter would result in

individual phases with consequent interference. A sensible

solution to this problem is to use a two-way timing protocol

such as PTP to cancel out the path delay and provide a

common phase at each transmitter. This can be achieved even

on legacy packet networks that have no on-path support,

making it possible to time wireless transmitters over existing

packet networks.

For occasions when the timing packet stream fails, the

ACS9550T includes a holdover mode to maintain timing within

defined limits until the stream can be re-established.

System diagram

FINAL PRODUCT BRIEF

Features

? Fully integrated - IEEE1588 (PTP) Slave function providing

reference frequency output. Time-of-Day (ToD) output and

one pulse per second (PPS) output. Powerful integrated

processor running clock recovery algorithm (a combination

of PTP and adaptive packet delay filtering).

? PTP Grandmaster selection - configured or automatic

(according to the PTP Best Master Clock algorithm).

Multiple Grandmasters supported.

? Powerful network delay analysis delivers full time

alignment in the slave over hostile networks (including

Layer 2 & 3 routed).

? Dynamic adaptation to delay variations. Tolerant to network

loading changes (ramps and steps), routing changes and

temporary outages.

? Operational support - unicast and multicast operation.

? Configurable DiffServ codepoint - for high priority packet

routing.

? Precision holdover.

? Interfaces for:

Time-aligned output pair:

1 PPS and 125 MHz divided by n (n = 4 to 125000).

Six frequency-aligned outputs:

1 Hz and programmable frequency 1 kHz to 62.5 MHz.

Media Independent Interface (Ethernet port).

Serial peripheral interface (SPI).

Local oscillator (reference frequency for internal clock

frequency).

SRAM port.

JTAG boundary scan port.

? Supports operation with a local oscillator accurate to

±20 ppm or better.

? Time alignment performance better than ±1 ? s on a

managed 5-switch GbE network under G.8261 4 test

conditions.*

? Frequency alignment performance better than ±10 ppb on

a managed 5-switch GbE network under G.8261 4 test

conditions.*

? Standard compliance - IEEE 1588 v2 1 , G.8261 4 .

? BGA package - 360 pin, 20 mm x 20 mm, 1 mm pitch.

? Lead-free version available - RoHS 5 and WEEE 6 compliant.

This is an indication of Semtech tested performance and is not

guaranteed across all types of switches and network conditions. Please

contact Semtech ToPSync TM support for further details.

ACS9550TPB_US, Revision 04, February 2010

?2010 Semtech Corp.

Page 1

www.semtech.com

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