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DDR3THIN-MN-XXX 72 Doc. Rev. 1.11
the differential pair by removed. The added capacitance of the logic analyzer compensates for
this missing capacitor.
7.5 Thresholds
Analog waveforms and their associated thresholds viewed using the Tektronix Analog Mux will
display amplitudes and thresholds that are not an exact representation of the actual analog
waveform. The Nexus passive probes used on DDR3 NEXVu and Interposer products are
designed to supply maximum voltage swing to the Logic analyzer to insure correct digital signal
swing capture at the high DDR3 rates. While the Tektronix active P69xx and P68xx series of
probe, being general purpose probes, divide the input voltage swing by 20 the passive probes
from Nexus divide the signals by approximately 7.5. Since the divide value is different than the
standard Tektronix probe the voltage swing and offset will be higher than expected, and the
thresholds will be different. Instead of the expected 0.75 threshold of approximately 1.9V
threshold will be required. This was designed specifically for DDR3 signals to allow the best
possible capture of the digital representation of these signals. Viewing the output of the Logic
Analyzer analog mux should be used as a tool to provide fine adjustment of the logic analyzer
signal Vref. The threshold value determined in this manner should be used as the threshold
setting for the Nexus DDR3 product. Please note: Only the vertical resolution is affected by the
Nexus passive probes.