AM79C978AKCW Ver la hoja de datos (PDF) - Advanced Micro Devices
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AM79C978AKCW Datasheet PDF : 256 Pages
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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
Output
Input Pin
Pin
XCLK/XTAL Clock Source
XTAL1
XTAL2
0
20-MHz Crystal
60-MHz Oscillator/
XTAL1 Don’t Care
1
External CLK
Source
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
Parameter
Min Nom Max Units
1. Parallel Resonant
Frequency
20
MHz
2. Resonant Frequency Error -50
+50 PPM
3. Change in Resonant
Frequency With Respect To -40
Temperature (0-70°C)*
+40 PPM
4. Crystal Load Capacitance 15 18 33 pF
5. Motional Crystal
Capacitance (C1)
0.022
pF
6. Internal Equivalent Series
Resistance
50 ohm
7. Shunt Capacitance
7 pF
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.
Am79C978A
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