VSC8201 Datasheet, PDF (1/21 Pages) Vitesse Semiconductor Corporation – Single Port 10/100/1000BASE-Tand 1000BASE-X PHY

SimpliPHY^® VSC8201
PCB Design and Layout Guide
Single Port 10/100/1000BASE-Tand 1000BASE-X PHY
Introduction
This purpose of this application note in conjunction with the VSC8201 Datasheet is to provide information to assist in the design and lay-
out of the VSC8201 Gigabit Ethernet Transceiver.
Power Supply Organization and Decoupling
The VSC8201 requires a 3.3v and a 1.5v power supply source for operation using GMII, MII or TBI MAC interfaces. In RGMII and RTBI
modes, an additional 2.5v supply is needed as specified by the RGMI/RTBI standard. The VSC8201 can be powered using the following
options:
• 2 separate supplies, 3.3v and 1.5v respectively.
• A single 3.3v supply. This is done by using the optional on-chip regulator control circuit, which drives a simple external series pass
type supply regulator (MOSFET) to generate the 1.5v core power supply.
PCB Power Plane Organization
It is recommended that the PCB power plane(s) in a system be divided into four separate regions:
Table 1: Power Supply Plane Regions
PCB Power ^Description
Plane
Nominal
Supply Voltage
Current^a
Typ
Max
LQFP Supply Names^b
V+IO
Digital Input/Output
buffer supply
3.3v/2.5v
8mA
11mA
VDDIO
V+A33
Filtered analog 3.3v 3.3v
supply
101mA
111mA
TXVDD, VDDREC33,
VDDPLL33
V+A15
Filtered analog 1.5v 1.5v
supply
41mA
48mA
VDDREC15, VDDPLL15
V+DIG
Digital core supply
1.5v
350mA
423mA
VDDDIG
a. Test conditions: Room temperature (25^oC), 1000BASE-T data, full duplex, minimum IPG, 64-byte packets, RGMII MAC active, excluding
regulator power dissipation but including external twisted pair termination; all worst case current figures have all nominal power supplies
scaled by +5%.
b. Refer VSC8201 Datasheet to correlate supply names with part pin numbers.
Power Supply Filtering and Decoupling
For best performance, each power supply region should contain capacitors for both bulk decoupling and for local high-frequency decou-
pling. This is summarized in the following tables:
Rev. 1.6.3 - 9/29/04
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