Pci Adapter Card Power Source; Vcc5Ref Pin Requirement; Diff ); Vcc5Ref - Intel i960 Design Manual

9.3

PCI Adapter Card Power Source

Currently, PCI Adapter card vendors cannot rely on the PCI connector to provide 3.3V. Hence, any
adapter card designed with the
the processor power supply.
9.4 V
CC5REF
In mixed voltage systems that drive
pin must be connected to the system's 5V supply. To limit current flow into the V
is a limit to the voltage differential between the V
differential between the V
this requirement ensures proper operation and guarantees component reliability. This limit applies
to power-up, power-down, and steady-state operation.
Table 9-15. V Specification for Dual-Power Supply Requirements (3.3 V, 5 V)
DIFF
Sym
V
V
DIFF
Difference
If the voltage difference requirements cannot be met due to system design limitations, an alternate
solution may be employed. As shown in
to limit the current into the V
pin does not exceed the maximum rating for this pin.
Figure 9-20. V
CC5REF
This resistor is not necessary in systems that can guarantee the V
3.3V-only systems and systems that drive pins from 3.3V logic, connect the V
to the 3.3V V
Design Guide
®
Intel 80960RM/RN Processor 5 V and 3.3 V Design Considerations
RM/RN I/O processor
Pin Requirement (V
pin and its 3.3V V
CC5REF
Parameter Min Max
-V
CC5 CC
2.25
CC5REF
Current-Limiting Resistor
+5V (±0.25V)
plane.
CC
Intel® i960® RM/RN I/O Processor
must design an on-board 3.3V regulator for
)
DIFF
RM/RN I/O processor inputs in excess of 3.3V, the V
pin and the other V
CC5REF
pins should never exceed 2.25V. Meeting
CC
Table 9-15
Unit
V input should not exceed V
CC5REF
V 2.25V during power-up and power-down, or during
steady-state operation.
Figure 9-20, a 100 ohm 0.5W series resistor may be used
*
pin. This resistor ensures that current drawn by the V
VCC5REF Pin
100 Ω
(±5%, 0.5 W)
CC5REF
pin, there
CC5REF
pins. The voltage
CC
outlines this requirement.
Notes
by more than
CC
specification. Also, in
DIFF
pin directly
CC5REF
CC5REF
37