am79c970 Advanced Micro Devices, am79c970 Datasheet - Page 153

• Manufacturer Part Number: am79c970
• Description: Pcnettm-pci Single-chip Ethernet Controller For Pci Local Bus
• Manufacturer: Advanced Micro Devices

To determine the value for the resistor and capacitor,
the formula is:
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 .
1-1020
AMD
PCnet-PCI
VDD plane
R * C
AVDD2
AVSS2
2.7
4.3
6.8
10
88
R
33 F
22 F
15 F
10 F
C
33 uF to 10 uF
1
to 10
VSS plane
18220C-53
Am79C970
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 men-
tioned, 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.