EDJ1108BABG, EDJ1116BABG
VREF Tolerances
The dc-tolerance limits and ac-noise limits for the reference voltages VREFCA and VREFDQ are shown in Figure
VREF(DC) Tolerance and VREF AC-Noise Limits. It shows a valid reference voltage VREF(t) as a function of time.
(VREF stands for VREFCA and VREFDQ likewise).
VREF(DC) is the linear average of VREF(t) over a very long period of time (e.g. 1 sec). This average has to meet the
min/max requirements in the table of(Single-Ended AC and DC Input Levels for Command and Address).
Furthermore VREF(t) may temporarily deviate from VREF(DC) by no more than +/- 1% VDD.
VREF(DC) Tolerance and VREF AC-Noise Limits
The voltage levels for setup and hold time measurements VIH(AC), VIH(DC), VIL(AC) and VIL(DC) are dependent
on VREF.
VREF shall be understood as VREF(DC), as defined in figure above, VREF(DC) Tolerance and VREF AC-Noise
Limits.
This clarifies that DC-variations of VREF affect the absolute voltage a signal has to reach to achieve a valid high or
low level and therefore the time to which setup and hold is measured. System timing and voltage budgets need to
account for VREF(DC) deviations from the optimum position within the data-eye of the input signals.
This also clarifies that the DRAM setup/hold specification and derating values need to include time and voltage
associated with VREF AC-noise. Timing and voltage effects due to ac-noise on VREF up to the specified limit (±1%
of VDD) are included in DRAM timings and their associated deratings.
Data Sheet E1248E40 (Ver. 4.0)
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ELPIDA [ ELPIDA MEMORY ]
