Datasheet

Note that while Address/command and DQ signal requirements are with respect to VREF, the single-ended
components 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 VSEL max, VSEH min has no bearing on
timing, but adds a restriction on the common mode characteristics of these signals.
Single-ended levels for CK, DQS, CK, DQS
NOTE :
1. For CK, CK use VIH/VIL(AC) of address/command; for strobes (DQS, DQS) use VIH/VIL(AC) of DQs.
2. VIH(AC)/VIL(AC) for DQs is based on VREFDQ; VIH(AC)/VIL(AC) for address/command is based on VREFCA; if a
reduced AC-high or AC-low level is used for a signal group, then the reduced level applies also here.
3. These values are not defined, however the single-ended components of differential signals CK, CK
, DQS, DQS need
to be within the respective limits (VIH(DC) max, VIL(DC) min) for single-ended signals as well as the limitations for
overshoot and undershoot. Refer to "Overshoot and Undershoot specifications”.
Symbol Parameter Min. Max. Units Notes
VSEH
Single-ended high-level for strobes (VDD/2) + 0.175 NOTE 3 V 1,2
Single-ended high-level for CK, CK
(VDD/2) + 0.175 NOTE 3 V 1,2
VSEL
Single-ended low-level for strobes NOTE 3 (VDD/2) - 0.175 V 1,2
Single-ended low-level for CK, CK NOTE 3 (VDD/2) - 0.175 V 1,2
Single-ended requirement for differential signals
VSS or VSSQ
VDD or VDDQ
VSEL max
VSEH min
VSEH
VSEL
time
VDD/2 or VDDQ/2
CK or DQS
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