Intel Pentium III BX80525U550512E データシート
製品コード
BX80525U550512E
Datasheet
41
Signal Quality Specifications
3.2
AGTL+ and Non-AGTL+ Overshoot/Undershoot
Specifications and Measurement Guidelines
Specifications and Measurement Guidelines
Overshoot/Undershoot is the absolute value of the maximum voltage differential across the input
buffer relative termination voltage (V
buffer relative termination voltage (V
TT
). The overshoot/undershoot guideline limits transitions
beyond V
TT
or V
SS
due to the fast signal edge rates. The processor can be damaged by repeated
overshoot/undershoot events on 1.5 V or 2.5 V tolerant buffers if the charge is large enough (i.e., if
the overshoot/undershoot is great enough). Determining the impact of an overshoot/undershoot
condition requires knowledge of the Magnitude, the Pulse Duration, and the Activity Factor.
the overshoot/undershoot is great enough). Determining the impact of an overshoot/undershoot
condition requires knowledge of the Magnitude, the Pulse Duration, and the Activity Factor.
When performing simulations to determine impact of overshoot/undershoot, ESD diodes must be
properly characterized. ESD protection diodes do not act as voltage clamps and will not provide
overshoot/undershoot protection. ESD diodes modeled within the Intel provided Intel
properly characterized. ESD protection diodes do not act as voltage clamps and will not provide
overshoot/undershoot protection. ESD diodes modeled within the Intel provided Intel
®
Pentium
®
III Processor I/O Buffer Models do not clamp overshoot/undershoot and will yield correct
simulation results. If other I/O buffer models are being used to characterize Pentium III processor
performance, care must be taken to ensure that ESD models do not clamp extreme voltage levels.
The Intel-provided Pentium
simulation results. If other I/O buffer models are being used to characterize Pentium III processor
performance, care must be taken to ensure that ESD models do not clamp extreme voltage levels.
The Intel-provided Pentium
®
III Processor I/O Buffer Models also contains I/O capacitance
characterization. Therefore, removing the ESD diodes from the I/O buffer model will impact
results and may yield excessive overshoot/undershoot.
results and may yield excessive overshoot/undershoot.
3.2.1
Overshoot/Undershoot Magnitude
Overshoot/Undershoot Magnitude describes the maximum potential difference between a signal
and its voltage reference level, V
and its voltage reference level, V
SS
(overshoot) and V
TT
(undershoot). While overshoot can be
measured relative to V
SS
using one probe (probe to signal - GND lead to V
SS
), undershoot must be
measured relative to V
TT
. This could be accomplished by simultaneously measuring the V
TT
plane
while measuring the signal undershoot. The true waveform can then be calculated by the
oscilloscope itself or by the following oscilloscope date file analysis:
oscilloscope itself or by the following oscilloscope date file analysis:
Converted Undershoot Waveform = V
TT
– Signal_measured
Note:
The Converted Undershoot Waveform appears as a positive (overshoot) signal.
Note:
Overshoot (rising edge) and undershoot (falling edge) conditions are separate and their impact
must be determined independently.
must be determined independently.
After the conversion, the Undershoot/Overshoot Specifications (
through
) can be
applied to the Converted Undershoot Waveform using the same Magnitude and Pulse Duration
Specifications (
Specifications (
through
) as with an overshoot waveform.
Overshoot/undershoot magnitude levels must observe the Absolute Maximum Specifications
(
(
). These specifications must not be violated at any time regardless of
bus activity or system state. Within these specifications are threshold levels that define different
allowed Pulse Durations. Provided that the magnitude of the overshoot/undershoot is within the
Absolute Maximum Specifications, the impact of the Overshoot/Undershoot Magnitude may be
determined based upon the Pulse Duration and Activity Factor.
allowed Pulse Durations. Provided that the magnitude of the overshoot/undershoot is within the
Absolute Maximum Specifications, the impact of the Overshoot/Undershoot Magnitude may be
determined based upon the Pulse Duration and Activity Factor.