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| HYB18M256320CF Datasheet, PDF (18/26 Pages) Qimonda AG – DRAMs for Mobile Applications | |||
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Internet Data Sheet
HY[B/E]18M256[16/32]0CF
256-Mbit DDR Mobile-RAM
17) tDQSQ consists of data pin skew and output pattern effects, and p-channel to n-channel variation of the output drivers for any given cycle.
18) The specific requirement is that DQS be valid (HIGH, LOW, or some point on a valid transition) on or before this CK edge. A valid transition
is defined as monotonic and meeting the input slew rate specifications of the device. When no writes were previously in progress on the
bus, DQS will be transitioning from Hi-Z to logic LOW. If a previous write was in progress, DQS could be HIGH, LOW, or transitioning from
HIGH to LOW at this time, depending on tDQSS.
19) The maximum limit for this parameter is not a device limit. The device operates with a greater value for this parameter, but system
performance (bus turnaround) will degrade accordingly.
20) A low level on DQS may be maintained during High-Z states (DQS drivers disabled) by adding a weak pull-down element in the system.
It is recommended to turn off the weak pull-down element during read and write bursts (DQS drivers enabled).
21) These parameters account for the number of clock cycles and depend on the operating frequency, as follows:no. of clock cycles = specified
delay / clock period; round to the next higher integer.
22) tDAL = (tWR / tCK) + (tRP / tCK): for each of the terms above, if not already an integer, round to the next higher integer.
23) tWTR is also referred to as tCDLR
24) A maximum of eight AUTOREFRESH commands can be posted to the DDR Mobile-RAM device, meaning that the maximum absolute
interval between any Refresh command and the next Refresh command is 8 * tREFI.
) /
: / HM S
P &
FIGURE 3
Measurement with Reference Load
Parameter
Maximum peak amplitude allowed for overshoot
Maximum peak amplitude allowed for undershoot
Maximum overshoot area above VDD
Maximum undershoot area below VSS
TABLE 12
AC Overshoot / Undershoot Specification
Max.
Unit Note
0.5
V
â
0.5
V
â
3.0
V-ns â
3.0
V-ns â
FIGURE 4
AC Overshoot and Undershoot Definition
/V E R S HO O T !R E A
6$ $
- A X !M P L I T UD E 6
- A X !R E A 6
N S
63 3
5N DE R S HO O T !R E A
4I M E NS
Rev.1.44, 2007-07
18
06262007-JK8G-48BV
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