AM79C978AVCW datasheet(27/256 Pages) AMD

27 / 256 page

Am79C978A

HomePNA PHY Network Interface

HRTXRXP/HRTXRXN

Serial Receive Data

Input/Output

These pins accept the receive input data from the mag-

netics module and carry the transmit output data. A

100-W resistor should be placed between these pins.

Clock Interface

XCLK/XTAL

External Clock/Crystal Select

Input

When HIGH, an external 60-MHz clock source is se-

lected bypassing the crystal circuit and clock trippler.

When LOW, a 20-MHz crystal is used instead. The

following table illustrates how this pin works.

Table 2.

External Clock/Crystal Select

XTAL1

Crystal Oscillator In

Input

The internal clock generator utilizes either a 20-MHz

crystal that is attached to pins XTAL1 and XTAL2 or a

60-MHz clock source connected to XTAL1. This pin is

not 5 V tolerant, and the 60 MHz clock source should

be from a 3.3 V source, not a 5 V clock source.

XTAL2

Crystal Oscillator Out

Output

The internal clock generator utilizes either a 20-MHz

crystal that is attached to pins XTAL1 and XTAL2 or a

60-MHz clock source connected to XTAL1.

External Crystal Characteristics

When using a crystal to drive the oscillator, the fol-

lowing crystal specification in Table 3 may be used to

ensure less than ±0.5 ns jitter at DO±.

Table 3.

Crystal Characteristics

Note: *Requires trimming specification; not trimmed is

50 PPM total.

Power Supply

VDDB

I/O Buffer Power (4 Pins)

+3.3 V Power

These pins are the power supply pins that are used by

the input/output buffer drivers. All VDDB pins must be

connected to a +3.3 V supply.

VDD_PCI

PCI I/O Buffer Power (9 Pins)

+3.3 V Power

These pins are the power supply pins that are used

by the PCI input/output buffer drivers (except PME

driver). All VDD_PCI pins must be connected to a

+3.3 V supply.

VSSB

I/O Buffer Ground (15 Pins)

Ground

These pins are the ground pins that are used by the

input/output buffer drivers.

VDD

Digital Power (7 Pins)

+3.3 V Power

These pins are the power supply pins that are used

by the internal digital circuitry. All VDD pins must be

connected to a +3.3 V supply.

VSS

Digital Ground (7 Pins)

Ground

There are seven ground pins that are used by the internal

digital circuitry.

Input Pin

Output

XCLK/XTAL

Clock Source

XTAL1

XTAL2

20-MHz Crystal

XTAL1

Don’t Care

60-MHz Oscillator/

External CLK

Source

Parameter

Min

Nom

Max Units

1. Parallel Resonant

Frequency

MHz

2. Resonant Frequency Error

-50

+50

PPM

3. Change in Resonant

Frequency With Respect To

Temperature (0-70°C)*

-40

+40

PPM

4. Crystal Load Capacitance

5. Motional Crystal

Capacitance (C1)

0.022

6. Internal Equivalent Series

Resistance

ohm

7. Shunt Capacitance

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