VSC8664 Design and Layout Guide
VPPD-01990 ENT-AN0144 Application Note Revision 1.0
Contents
1 Revision History ............................................................................................................................. 1
1.1 Revision 1.0 ........................................................................................................................................ 1
2 Introduction ................................................................................................................................... 2
2.1 References .......................................................................................................................................... 2
2.1.1 Vitesse Documents .................................................................................................................................. 2
2.1.2 IEEE Standards ......................................................................................................................................... 2
2.1.3 External Documents ................................................................................................................................ 2
3 Ground Considerations ................................................................................................................. 3
3.1 Ground Isolation ................................................................................................................................. 3
3.2 Bob Smith Termination ....................................................................................................................... 3
4 Power Considerations ................................................................................................................... 4
4.1 Power Supply Planes .......................................................................................................................... 4
4.2 Analog Power Plane Filtering .............................................................................................................. 4
4.3 Local Decoupling ................................................................................................................................. 4
5 Thermal Considerations ................................................................................................................ 5
6 Copper Interface ........................................................................................................................... 7
6.1 Layout Considerations ........................................................................................................................ 7
6.2 RJ-45 Connectors ................................................................................................................................ 7
7 SerDes Interface ............................................................................................................................ 9
7.1 Design Rules ....................................................................................................................................... 9
7.2 AC Coupling Capacitors ....................................................................................................................... 9
7.3 SerDes Media ..................................................................................................................................... 9
8 Miscellaneous Design Considerations .......................................................................................... 10
8.1 REF_FILT / REF_REXT Pins ................................................................................................................. 10
8.2 Clock Inputs ...................................................................................................................................... 10
8.2.1 Crystal Clock Option .............................................................................................................................. 11
8.2.2 25 MHz Reference Clock Option ........................................................................................................... 11
8.2.3 125 MHz Reference Clock Option ......................................................................................................... 11
8.2.4 Clock Power Supply Filtering ................................................................................................................. 12
8.3 CLKOUT pin ....................................................................................................................................... 12
8.4 Serial Management Interface (SMI) ................................................................................................. 12
8.5 LEDs .................................................................................................................................................. 13
8.6 GPIO Pins .......................................................................................................................................... 13
8.7 Optional CMODE Interface ............................................................................................................... 13
9 Bringing Up the Device ................................................................................................................ 14