24
Operating the Probe
130 ohm Resistive Signal Pin (orange) and Solder-down Ground Lead
Eye opening
The eye opening at the logic analyzer is the truest measure of an analyzer's ability
to accurately capture data. Seeing the eye opening at the logic analyzer is
possible with Eye Scan. Eye opening helps you know how much margin the logic
analyzer has, where to sample and at what threshold. Any probe response that
exhibits overshoot and ringing, probe non-flatness, noise and other issues all
deteriorate the eye opening seen by the logic analyzer. The following eye
diagrams were measured using Eye Scan probed mid-bus on a 50
Ω
transmission
line load terminated at the receiver. The data patterns were generated using a
2
23
−
1 pseudo random bit sequence (PRBS). These measurements show the
remaining eye opening at the logic analyzer while using the 130
Ω
resistive signal
pin (orange) and solder-down ground lead configuration.
Eye opening measurement schematic
The logic analyzer Eye Scan measurement uses the same circuitry as the
synchronous state mode analysis. Therefore, the eye openings measured are
exact representations of what the logic analyzer sees and operates on in state
mode. The following measurements demonstrate how the eye opening starts to
collapse as the clock rate is increased. At 1500 Mb/s, the eye opening is noticeably
deteriorating as jitter on the transitions increase and voltage margins decrease.
As demonstrated by the last eye diagram, the 130
Ω
resistive signal pin and
solder-down ground lead configuration still has a usable eye opening at 1250
Mb/s and minimum signal swing.
E5382A
Probe
Z0=50
Ω
Rterm
Driver
Receiver
Rsource
PRBS
output
50
Ω
Z0=50
Ω
50
Ω
Logic
Analyzer
w/ EyeScan
Summary of Contents for E5382A
Page 4: ...4 Contents ...
Page 5: ...1 General Information ...
Page 13: ...2 Operating the Probe ...
