PM5347 datasheet(233/302 Pages) PMC

233 / 302 page

PM5347 S/UNI-PLUS

DATA SHEET

PMC-941033

ISSUE 6

SATURN USER NETWORK INTERFACE PLUS

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

217

OPERATION

This section presents PCB design recommendations, tutorial information on the

SONET/SDH transmission convergence sublayer for ATM, the SCI-PHY™

compliant cell data structures, and operating details for the JTAG boundary scan

feature.

12.1

Board Design Recommendations

The noise environment and signal integrity are often the limiting factors in system

performance. Therefore, the following board design guidelines

must be followed

in order to ensure proper operation.

1. Connect digital and analog grounds together at a point where the ground

reference is clean and as free as possible of digital return currents. Typically,

this means as close as possible to the PCB connector where ground is

brought into the card.

2. Provide separate +5 volt analog transmit, +5 volt analog receive, and +5 volt

digital supplies, but otherwise connect the supply voltages together at a point

where the supply is clean and as free as possible of digitally induced

switching noise. Typically, this means as close as possible to the PCB

connector where +5 volts is brought into the card. In some systems separate

regulation is required for the transmit and receive analog supplies.

3. Ferrite beads are not advisable in digital switching circuits because inductive

spiking (di/dt noise) is introduced into the power rail. Simple RC filtering is

probably the best approach provided care is taken to ensure the IR drop in

the resistor does not lower the supply voltage below the recommended

operating voltage.

4. Ferrite beads are recommended for TAVD1, TAVD2, RAVD1 and RAVD2.

5. Separate high-frequency decoupling capacitors are recommended for each

analog power (TAVD1, TAVD2, RAVD1 and RAVD2) pin as close to the

package pin as possible. Separate decoupling is required to prevent the

transmitter from coupling noise into the receiver and to prevent transients

from coupling into the reference circuitry powered by TAVD1 and RAVD1.

6. The high speed serial streams (TXD+/- and RXD+/) must be routed with

controlled impedance circuit board traces and must be terminated with a

PM5347 Datasheet(PDF) 233 Page - PMC-Sierra, Inc