AM79C970A datasheet(203/219 Pages) AMD

203 / 219 page

AMD

B-2

Am79C970A

19436A-58

AVDD2

AVSS2

VDD plane

VSS plane

µF to 10 µF

Ω to 10 Ω

PCnet-PCI II

0.1

µF

To determine the value for the resistor and capacitor,

the formula is:

R * C

≥ 88

Where R is in Ohms and C is in microfarads. Some pos-

sible combinations are given below. To minimize the

voltage drop across the resistor, the R value should not

be more than 10

Ω.

2.7

Ω

µF

4.3

Ω

µF

6.8

Ω

µF

Ω

µF

AVSS2 and AVDD2/AVDD4: These pins provide power

and ground for the AUI and twisted pair receive circuitry.

In addition, as mentioned earlier, AVSS2 and AVDD2

provide power and ground for the phase-lock loop por-

tion of the chip. Except for the filter circuit already

mentioned, no specific decoupling is necessary on

these pins.

AVDD1: AVDD1 provides power for the control and in-

terface logic in the PLL. Ground for this logic is provided

by digital ground pins. No specific decoupling is neces-

sary on this pin.

Special Note for Adapter Cards: In adapter card de-

signs, it is important to utilize all available power and

ground pins available on the bus edge connector. In

addition, the connection from the bus edge connector to

the power or ground plane should be made through

more than one via and with wide traces (15 mils desir-

able) wherever possible. Following these recommenda-

tions results in minimal inductance in the power and

ground paths. By minimizing this inductance, ground

bounce is minimized.

See also the PCnet Family Board Design and Layout

Recommendations applications note (PID# 19595) for

additional information.

AM79C970A Datasheet(PDF) 203 Page - Advanced Micro Devices

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