W3EG7218S-AD4 Datasheet, PDF (9/13 Pages) White Electronic Designs Corporation – 128MB - 16Mx72 DDR SDRAM UNBUFFERED w/PLL

White Electronic Designs
W3EG7218S-AD4
-BD4
PRELIMINARY
Notes
1. All voltages referenced to VSS.
2. Tests for AC timing, IDD, and electrical AC and DC characteristics may be
conducted at nominal reference/supply voltage levels, but the related specifications
and device operation are guaranteed for the full voltage range specified.
3. Outputs measured with equivalent load:
VTT
Output
(VOUT)
50Ω
Reference
Point
30pF
4. AC timing and IDD tests may use a VIL-to-VIH swing of up to 1.5V in the test
environment, but input timing is still referenced to VREF (or to the crossing point for
CK/CK#), and parameter specifications are guaranteed for the specified AC input
levels under normal use conditions. The mini-mum slew rate for the input signals
used to test the device is 1V/ns in the range between VIL(AC) and VIH(AC).
5. The AC and DC input level specifications are as defined in the SSTL_2 Standard
(i.e., the receiver will effectively switch as a result of the signal crossing the AC
input level, and will remain in that state as long as the signal does not ring back
above [below] the DC input LOW [HIGH] level).
6. VREF is expected to equal VCCQ/2 of the transmitting device and to track variations
in the DC level of the same. Peak-to-peak noise (non-common mode) on Vref may
not exceed ±2 percent of the DC value. Thus, from VCCQ/2, Vref is allowed ±25mV
for DC error and an additional ±25mV for AC noise. This measurement is to be
taken at the nearest VREF bypass capacitor.
7. VTT is not applied directly to the device. VTT is a system supply for signal
termination resistors, is expected to be set equal to VREF and must track variations
in the DC level of VREF.
8. IDD is dependent on output loading and cycle rates. Specified values are obtained
with mini-mum cycle time at CL = 2 for -26A and -202, CL = 2.5 for -335 and -265
with the outputs open.
9. Enables on-chip refresh and address counters.
10. IDD specifications are tested after the device is properly initialized, and is averaged
at the defined cycle rate.
11. This parameter is sampled. VCC = +2.5V ±0.2V, VCCQ = +2.5V ±0.2V, VREF = VSS, f
= 100 MHz, TA = 25°C, VOUT(DC) = VCCQ/2, VOUT (peak to peak) = 0.2V. DM input is
grouped with I/O pins, reflecting the fact that they are matched in loading.
12. For slew rates < 1 V/ns and ≥ to 0.5 Vns. If the slew rate is < 0.5V/ns, timing
must be derated: tIS has an additional 50ps per each 100 mV/ns reduction in slew
rate from 500 mV/ns, while tIH is unaffected. If the slew rate exceeds 4.5 V/ns,
functionality is uncertain. For -335, slew rates must be 0.5 V/ns.
13. The CK/CK# input reference level (for timing referenced to CK/CK#) is the point at
which CK and CK# cross; the input reference level for signals other than CK/CK# is
VREF.
14. Inputs are not recognized as valid until VREF stabilizes. Exception: during the period
before VREF stabilizes, CKE < 0.3 x VCCQ is recognized as LOW.
15. The output timing reference level, as measured at the timing reference point
indicated in Note 3, is VTT.
16. tHZ and tLZ transitions occur in the same access time windows as data valid
transitions. These parameters are not referenced to a specific voltage level, but
specify when the device output is no longer driving (HZ) or begins driving (LZ).
17. The intent of the Don’t Care state after completion of the postamble is the DQS-
driven signal should either be high, low, or high-Z and that any signal transition
within the input switching region must follow valid input requirements. That is, if
DQS transitions high [above VIHDC (MIN)] then it must not transition low (below
VIHDC) prior to tDQSH (MIN).
18. This is not a device limit. The device will operate with a negative value, but system
performance could be degraded due to bus turnaround.
19. It is recommended that DQS be valid (HIGH or LOW) on or before the WRITE
command. The case shown (DQS going from High-Z to logic LOW) applies when
no WRITEs were previously in progress on the bus. If a previous WRITE was in
progress, DQS could be HIGH during this time, depending on tDQSS.
20. MIN (tRC or tRFC) for IDD measurements is the smallest multiple of tCK that meets
the minimum absolute value for the respective parameter. tRAS (MAX) for IDD
measurements is the largest multiple of tCK that meets the maximum absolute value
for tRAS.
21. The refresh period 64ms. This equates to an average refresh rate of 15.625µs
128MB. However, an AUTO REFRESH command must be asserted at least once
every 140.6µs 128MB; burst refreshing or posting by the DRAM controller greater
than eight refresh cycles is not allowed.
22. The valid data window is derived by achieving other specifications: tHP (tCK/2), tDQSQ,
and tQH (tQH = tHP - tQHS). The data valid window derates in direct porportion with
the clock duty cycle and a practical data valid window can be derived, as shown in
Figure 7, Derating Data Valid Window. The clock is allowed a maximum duty cycle
variation of 45/55, beyond which functionality is uncertain. The data valid window
derating curves are provided below for duty cycles ranging between 50/50 and
45/55.
23. Each byte lane has a corresponding DQS.
24. This limit is actually a nominal value and does not result in a fail value. CKE is
HIGH during REFRESH command period (tRFC [MIN]) else CKE is LOW (i.e., during
standby).
25. To maintain a valid level, the transitioning edge of the input must:
a. Sustain a constant slew rate from the current AC level through to the target AC
level, VIL(AC) or VIH(AC).
b. Reach at least the target AC level.
c. After the AC target level is reached, continue to maintain at least the target DC
level, VIL(DC) or VIH(DC).
26. JEDEC specifies CK and CK# input slew rate must be ≤ 1V/ns (2V/ns
differentially).
27. DQ and DM input slew rates must not deviate from DQS by more than 10 percent.
If the DQ/ DM/DQS slew rate is less than 0.5 V/ns, timing must be derated: 50ps
must be added to tDS and tDH for each 100 mv/ns reduction in slew rate. If slew
rate exceeds 4 V/ns, functionality is uncertain. For -335, slew rates must be ≥ 0.5
V/ns.
28. VCC must not vary more than 4 percent if CKE is not active while any bank is active.
29. The clock is allowed up to ±150ps of jitter. Each timing parameter is allowed to vary
by the same amount.
30. tHP min is the lesser of tCL minimum and tCH minimum actually applied to the device
CK and CK# inputs, collectively during bank active.
31. READs and WRITEs with auto precharge are not allowed to be issued until
tRAS(min) can be satisfied prior to the internal precharge command being issued.
32. Any positive glitch must be less than 1/3 of the clock and not more than +400mV or
2.9V, which ever is less. Any negative glitch must be less than 1/3 of the clock cycle
and not exceed either - 300mV or 2.2V, whichever is more positive.
November 2004
Rev. 1
9
White Electronic Designs Corporation • [phone] • www.wedc.com