Teledyne LeCroy QPHY-DDR2 - Manual (Page 40)

40
QPHY-DDR2-OM-E Rev A
not reported in the Jedec JESD79-2E standard. Therefore it is not selected in the standard configurations, but
only in the All Tests configuration.
Tests Requiring Single Ended Probing of Differential Signal
VOX(ac) , AC Differential Output Cross Point Voltage
The typical value of VOX(ac) is expected to be about 0.5 x VDDQ of the transmitting device and VOX(ac) is
expected to track variations in VDDQ . VOX(ac) indicates the voltage at which differential output signals must
cross. This test requires probing each half of a differential signal. This is only available in the configurations using
4 probes.
Figure 23. Differential signal levels [JESD79-2E figure 74]
Timing Tests
Read Bursts
tDQSQ, DQS-DQ Skew for DQS and Associated DQ Signals
Maximum skew between the DQS line and the associated DQ line within a read burst
Measure timing from DQS at VREF to DQ rising at VIH(ac)min and falling at VIL(ac)max.
Figure 24. Data output (read) timing [JESD79-2E figure 32]