Datasheet

Differential swing requirements for DQS (DQS – DQS#)
Table 107. Differential AC and DC Input Levels for DQS
Symbol
Parameter
DDR4-2400
DDR4-2666
Unit
Note
Min.
Max.
Min.
Max.
V
IHDiffPeak
V
IH.DIFF.Peak
Voltage
160
-
TBD
TBD
mV
1,2
V
ILDiffPeak
V
IL.DIFF.Peak
Voltage
-
-160
TBD
TBD
mV
1,2
Note 1. Used to define a differential signal slew-rate.
Note 2. These values are not defined; however, the differential signals DQS – DQS#, need to be within the respective limits Overshoot,
Undershoot Specification for single-ended signals.
Differential Input Cross Point Voltage
Table 108. Cross point voltage for DQS differential input signals
Symbol
Parameter
DDR4-2400/2666
Unit
Note
Min.
Max.
V
IX_DQS_Ratio
DQS and DQS# crossing relative to the midpoint of the DQS
and DQS# signal swings
-
25
%
1,2
V
DQSmid
_to_V
cent
V
DQSmid
offset relative to V
cent_DQ
(midpoint)
-
min(V
IHdiff
,50)
mV
3-5
Note 1. V
IX_DQS_Ratio
is DQS VIX crossing (V
IX_DQS
_FR
or V
IX_DQS
_RF
) divided by V
DQS_trans
. V
DQS_trans
is the difference between the lowest
horizontal tangent above V
DQSmid
of the transitioning DQS signals and the highest horizontal tangent below V
DQSmid
of the
transitioning DQS signals.
Note 2. V
DQSmid
will be similar to the V
REFDQ
internal setting value obtained during V
REF
Training if the DQS and DQs drivers and paths are
matched.
Note 3. The maximum limit shall not exceed the smaller of V
IHdiff
minimum limit or 50mV.
Note 4. V
IX
measurements are only applicable for transitioning DQS and DQS# signals when toggling data, preamble and highz states are
not applicable conditions.
Note 5. The parameter V
DQSmid
is defined for simulation and ATE testing purposes, it is not expected to be tested in a system.
AS4C256M16D4
Confidential
- 195 of 201 -
Rev.1.0 Aug.2019