Filter
Top Products
- 17 -
datasheet DDR3L SDRAM
Rev. 1.0
Unbuffered DIMM
11.3.3 Single-ended Requirements for Differential Signals
Each individual component of a differential signal (CK, DQS, CK, DQS) has also to comply with certain requirements for single-ended signals.
CK and CK
have to approximately reach V
SEH
min / V
SEL
max (approximately equal to the ac-levels ( V
IH
(AC) / V
IL
(AC) ) for ADD/CMD signals) in every
half-cycle.
DQS, DQS
have to reach V
SEH
min / V
SEL
max (approximately the ac-levels ( V
IH
(AC) / V
IL
(AC) ) for DQ signals) in every half-cycle proceeding and follow-
ing 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 V
IH
150(AC)/V
IL
150(AC) is used for ADD/CMD
signals, then these ac-levels apply also for the single-ended signals CK and CK
.
Figure 4. Single-ended requirement for differential signals
Note that while ADD/CMD and DQ signal requirements are with respect to V
REF
, the single-ended components of differential signals have a requirement
with respect to V
DD
/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 V
SEL
max, V
SEH
min has no bearing on timing, but adds a restriction on the common
mode characteristics of these signals.
[ Table 6 ] Single ended levels for CK, DQS, CK
, DQS
NOTE :
1. For CK, CK
use V
IH
/V
IL
(AC) of ADD/CMD; for strobes (DQS, DQS) use V
IH
/V
IL
(AC) of DQs.
2. V
IH
(AC)/V
IL
(AC) for DQs is based on V
REFDQ
; V
IH
(AC)/V
IL
(AC) for ADD/CMD is based on V
REFCA
; 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 signals CK, CK
, DQS, DQS need to be within the respective limits (V
IH
(DC) max, V
IL
(DC)min) for single-ended sig-
nals as well as the limitations for overshoot and undershoot. Refer to "Overshoot and Undershoot Specification"
Symbol Parameter
DDR3-800/1066/1333/1600
Unit NOTE
Min Max
V
SEH
Single-ended high-level for strobes
(V
DD
/2)+0.175
NOTE 3 V 1, 2
Single-ended high-level for CK, CK
(V
DD
/2)+0.175
NOTE 3 V 1, 2
V
SEL
Single-ended low-level for strobes NOTE 3
(V
DD
/2)-0.175
V1, 2
Single-ended low-level for CK, CK
NOTE 3
(V
DD
/2)-0.175
V1, 2
V
DD
or V
DDQ
V
SEH
min
V
DD
/2 or V
DDQ
/2
V
SEL
max
V
SEH
V
SS
or V
SSQ
V
SEL
CK or DQS
time