Intel 80960HD - Manual (Page 39)

80960HA/HD/HT
Datasheet 39
4.5 VCCPLL Pin Requirements
When the voltage on the VCCPLL power supply pin exceeds the V
CC
pin voltage by 0.5 V at any
time, including the power up and power down sequences, excessive currents may permanently
damage on-chip electrostatic discharge (ESD) protection diodes. The damage may accumulate over
multiple episodes.
Pragmatically, this problem only occurs when the VCCPLL and V
CC
pins are driven by separate
power supplies or voltage regulators. Applications that use one power supply for VCCPLL and
V
CC
are not typically at risk. Verify that your application does not allow the VCCPLL voltage to
exceed V
CC
by 0.5 V.
The VCCPL low-pass filter recommended in the Developer’s Manual does not promote this
problem.
Table 21. V
DIFF
Specification for Dual Power Supply Requirements (3.3 V, 5 V)
Sym Parameter Min Max Units Notes
V
DIFF
VCC5-V
CC
Difference
2.25 V
VCC5 input should not exceed V
CC
by more than 2.25 V during
power-up and power-down, or during steady-state operation.