Intel D2500 DF8064101055400 Data Sheet
Product codes
DF8064101055400
94
Datasheet - Volume 1 of 2
6
Signal Quality Specifications
Source synchronous data transfer requires the clean reception of data signals and their
associated strobes. Ringing below receiver thresholds, non-monotonic signal edges,
and excessive voltage swing will adversely affect system timings. Ringback and signal
non-monotonicity cannot be tolerated since these phenomena may inadvertently
advance receiver state machines. Excessive signal swings (overshoot and undershoot)
are detrimental to silicon gate oxide integrity, and can cause device failure if absolute
voltage limits are exceeded. Additionally, overshoot and undershoot can cause timing
degradation due to the build up of inter-symbol interference (ISI) effects.
For these reasons, it is important that the design ensures acceptable signal quality
across all systematic variations encountered in volume manufacturing.
This section documents signal quality metrics used to derive topology and routing
guidelines through simulation and for interpreting results for signal quality
measurements of actual designs.
6.1
Signal Quality Specifications and Measurement
Guidelines
Various scenarios have been simulated to generate a set of layout guidelines which are
available in the Next Generation Intel® Atom™ Processor based desktop platform
design guides.
provide the signal quality specifications for all processor signals for use in
simulating signal quality at the processor core silicon (pads).
overshoot, undershoot, and ringback measurements.
6.1.1
Overshoot/Undershoot Guidelines
Overshoot (or undershoot) is the absolute value of the maximum voltage above the
nominal high voltage (or below V
SS
) as shown in
. The overshoot guideline
limits transitions beyond V
TT
or V
SS
due to the fast signal edge rates. The processor can
be damaged by repeated overshoot or undershoot events on any input, output, or I/O
buffer if the charge is large enough (i.e., if the over/undershoot is great enough).
Permanent damage to the processor is the likely result of excessive overshoot/
undershoot.
When performing simulations to determine impact of overshoot and undershoot, ESD
diodes must be properly characterized. ESD protection diodes do not act as voltage
clamps and will not provide overshoot or undershoot protection. ESD diodes modelled
within Intel I/O buffer models do not clamp undershoot or overshoot and will yield
correct simulation results. If other I/O buffer models are being used to characterize the
interfaces, care must be taken to ensure that ESD models do not clamp extreme
voltage levels. Intel I/O buffer models also contain I/O capacitance characterization.
Therefore, removing the ESD diodes from an I/O buffer model will impact results and
may yield excessive overshoot/undershoot.