Teledyne-lecroy QPHY-DDR2 Manual do Utilizador descarregar pdf (Página 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]

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