Datasheet

Rev. 1.0/Sep. 2012 18
Single-ended requirements for differential signals
Each individual component of a differential signal (CK, DQS, DQSL, DQSU, CK, DQS, DQSL, of DQSU) has
also to comply with certain requirements for single-ended signals.
CK and CK have to approximately reach VSEHmin / VSELmax (approximately equal to the ac-levels (VIH
(ac) / VIL (ac)) for ADD/CMD signals) in every half-cycle.
DQS, DQSL, DQSU, DQS
, DQSL have to reach VSEHmin / VSELmax (approximately the ac-levels (VIH (ac)
/ VIL (ac)) for DQ signals) in every half-cycle preceding and following a valid transition.
Note that the applicable ac-levels for ADD/CMD and DQ’s might be different per speed-bin etc. E.g., if
VIH.CA(AC150)/VIL.CA(AC150) is used for ADD/CMD signals, then these ac-levels apply also for the single-
ended signals CK and CK
.
Single-ended requirements for differential signals.
Note that, while ADD/CMD and DQ signal requirements are with respect to Vref, the single-ended compo-
nents of differential signals have a requirement with respect to VDD / 2; this is nominally the same. the
transition of single-ended signals through the ac-levels is used to measure setup time. For single-ended
components of differential signals the requirement to reach VSELmax, VSEHmin has no bearing on timing,
but adds a restriction on the common mode characteristics of these signals.
VDD or VDDQ
VSEHmin
VDD/2 or VDDQ/2
VSEH
VSELmax
VSS or VSSQ
CK or DQS
VSEL
time