the differential pair by removed. The added capacitance of the logic analyzer compensates for this missing capacitor.
7.5 ThresholdsAnalog 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.
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