AM79C960 datasheet(29/127 Pages) AMD

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P R E L I M I N A R Y

AMD

1-371

Am79C960

PIN DESCRIPTION: POWER SUPPLIES

All power pins with a “D” prefix are digital pins connected

to the digital circuitry and digital I/O buffers. All power

pins with an “A” prefix are analog power pins connected

to the analog circuitry. Not all analog pins are quiet and

special precaution must be taken when doing board lay-

out. Some analog pins are more noisy than others and

must be separated from the other analog pins.

AVDD1–4

Analog Power (4 Pins)

Power

Supplies power to analog portions of the PCnet-ISA

controller.

Special attention should be paid to the

printed circuit board layout to avoid excessive noise on

these lines. These supply lines should be kept separate

from the DVDD supply pins and as far back to the power

supply as is practically possible. AVDD3 is an exception

and should be connected to DVDD supply and away

from remaining AVDD supply pins. See the table below

for more details.

AVSS1–2

Analog Ground (2 Pins)

Power

Supplies

ground reference to analog portions of

PCnet-ISA controller. Special attention should be paid

to the printed circuit board layout to avoid excessive

noise on these lines. These supply lines should be kept

separate from the DVSS ground pins and as far back to

the power supply as is practically possible. AVSS1 is an

exception and should be connected to DVSS supply and

away from remaining AVSS supply pins. See the table

below for more details.

DVDD1–6

Digital Power (6 Pins)

Power

Supplies power to digital portions of PCnet-ISA control-

ler. Four pins are used by Input/Output buffer drivers

and two are used by the internal digital circuitry.

DVSS1–12

Digital Ground (12 Pins)

Power

Supplies

ground

reference to digital portions of

PCnet-ISA controller. Ten pins are used by Input/Output

buffer drivers and two are used by the internal digital

circuitry.

Analog Power Pins and the Circuits to Which They are Connected

Analog

Power

Ground

Circuit

Comments

AVDD2

AVSS2

These pins are connected to the analog

These pins should be kept quiet. They

and

voltage reference circuit and VCO.

should be kept separated with low- and

AVDD4

high-frequency by-pass capacitors.

AVDD1

These pins are connected to analog

These pins are moderately quiet and

circuits such as AUI and Twisted Pair

should be connected to the VDD supply

receive logic.

a short distance away from the DVDD pins.

AVDD3

AVSS1

These pins are connected to the AUI and

These pins are more noisy and should be

Twisted Pair drivers.

connected to the DVDD/DVSS supplies.

AM79C960 Datasheet(PDF) 29 Page - Advanced Micro Devices

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