Internet Data Sheet
HYS64T256022EDL–[25F/2.5/3/3S/3.7]–B
Small Outline DDR2 SDRAM Modules
13) DAL = WR + RU{tRP(ns) / tCK(ns)}, where RU stands for round up. WR refers to the tWR parameter stored in the MRS. For tRP, if the result
of the division is not already an integer, round up to the next highest integer. tCK refers to the application clock period. Example: For
DDR2–533 at tCK = 3.75 ns with tWR programmed to 4 clocks. tDAL = 4 + (15 ns / 3.75 ns) clocks = 4 + (4) clocks = 8 clocks.
14) tDAL.nCK = WR [nCK] + tnRP.nCK = WR + RU{tRP [ps] / tCK.AVG[ps] }, where WR is the value programmed in the EMR.
15) Input waveform timing tDH with differential data strobe enabled MR[bit10] = 0, is referenced from the differential data strobe crosspoint to
the input signal crossing at the VIH.DC level for a falling signal and from the differential data strobe crosspoint to the input signal crossing
at the VIL.DC level for a rising signal applied to the device under test. DQS, DQS signals must be monotonic between VIL.DC.MAX and
VIH.DC.MIN. See Figure 3.
16) tDQSQ: Consists of data pin skew and output pattern effects, and p-channel to n-channel variation of the output drivers as well as output
slew rate mismatch between DQS / DQS and associated DQ in any given cycle.
17) These parameters are measured from a data strobe signal ((L/U/R)DQS / DQS) crossing to its respective clock signal (CK / CK) crossing.
The spec values are not affected by the amount of clock jitter applied (i.e. tJIT.PER, tJIT.CC, etc.), as these are relative to the clock signal
crossing. That is, these parameters should be met whether clock jitter is present or not.
18) Input waveform timing tDS with differential data strobe enabled MR[bit10] = 0, is referenced from the input signal crossing at the VIH.AC level
to the differential data strobe crosspoint for a rising signal, and from the input signal crossing at the VIL.AC level to the differential data strobe
crosspoint for a falling signal applied to the device under test. DQS, DQS signals must be monotonic between Vil(DC)MAX and Vih(DC)MIN. See
Figure 3.
19) If tDS or tDH is violated, data corruption may occur and the data must be re-written with valid data before a valid READ can be executed.
20) These parameters are measured from a data signal ((L/U)DM, (L/U)DQ0, (L/U)DQ1, etc.) transition edge to its respective data strobe signal
((L/U/R)DQS / DQS) crossing.
21) tHP is the minimum of the absolute half period of the actual input clock. tHP is an input parameter but not an input specification parameter.
It is used in conjunction with tQHS to derive the DRAM output timing tQH. The value to be used for tQH calculation is determined by the
following equation; tHP = MIN (tCH.ABS, tCL.ABS), where, tCH.ABS is the minimum of the actual instantaneous clock high time; tCL.ABS is the
minimum of the actual instantaneous clock low time.
22) tHZ and tLZ transitions occur in the same access time as valid data transitions. These parameters are referenced to a specific voltage level
which specifies when the device output is no longer driving (tHZ), or begins driving (tLZ) .
23) Input waveform timing is referenced from the input signal crossing at the VIL.DC level for a rising signal and VIH.DC for a falling signal applied
to the device under test. See Figure 4.
24) Input waveform timing is referenced from the input signal crossing at the VIH.AC level for a rising signal and VIL.AC for a falling signal applied
to the device under test. See Figure 4.
25) These parameters are measured from a command/address signal (CKE, CS, RAS, CAS, WE, ODT, BA0, A0, A1, etc.) transition edge to
its respective clock signal (CK / CK) crossing. The spec values are not affected by the amount of clock jitter applied (i.e. tJIT.PER, tJIT.CC
,
etc.), as the setup and hold are relative to the clock signal crossing that latches the command/address. That is, these parameters should
be met whether clock jitter is present or not.
26) tQH = tHP – tQHS, where: tHP is the minimum of the absolute half period of the actual input clock; and tQHS is the specification value under the
max column. {The less half-pulse width distortion present, the larger the tQH value is; and the larger the valid data eye will be.}
Examples: 1) If the system provides tHP of 1315 ps into a DDR2–667 SDRAM, the DRAM provides tQH of 975 ps minimum. 2) If the system
provides tHP of 1420 ps into a DDR2–667 SDRAM, the DRAM provides tQH of 1080 ps minimum.
27) tQHS accounts for: 1) The pulse duration distortion of on-chip clock circuits, which represents how well the actual tHP at the input is
transferred to the output; and 2) The worst case push-out of DQS on one transition followed by the worst case pull-in of DQ on the next
transition, both of which are independent of each other, due to data pin skew, output pattern effects, and pchannel to n-channel variation
of the output drivers.
28) tRPST end point and tRPRE begin point are not referenced to a specific voltage level but specify when the device output is no longer driving
(tRPST), or begins driving (tRPRE). Figure 2 shows a method to calculate these points when the device is no longer driving (tRPST), or begins
driving (tRPRE) by measuring the signal at two different voltages. The actual voltage measurement points are not critical as long as the
calculation is consistent.
29) When the device is operated with input clock jitter, this parameter needs to be derated by the actual tJIT.PER of the input clock. (output
deratings are relative to the SDRAM input clock.) For example, if the measured jitter into a DDR2–667 SDRAM has tJIT.PER.MIN = – 72 ps
and tJIT.PER.MAX = + 93 ps, then tRPRE.MIN(DERATED) = tRPRE.MIN + tJIT.PER.MIN = 0.9 x tCK.AVG – 72 ps = + 2178 ps and tRPRE.MAX(DERATED) = tRPRE.MAX
+ tJIT.PER.MAX = 1.1 x tCK.AVG + 93 ps = + 2843 ps. (Caution on the MIN/MAX usage!).
30) When the device is operated with input clock jitter, this parameter needs to be derated by the actual tJIT.DUTY of the input clock. (output
deratings are relative to the SDRAM input clock.) For example, if the measured jitter into a DDR2–667 SDRAM has tJIT.DUTY.MIN = – 72 ps
and tJIT.DUTY.MAX = + 93 ps, then tRPST.MIN(DERATED) = tRPST.MIN + tJIT.DUTY.MIN = 0.4 x tCK.AVG – 72 ps = + 928 ps and tRPST.MAX(DERATED) = tRPST.MAX
+ tJIT.DUTY.MAX = 0.6 x tCK.AVG + 93 ps = + 1592 ps. (Caution on the MIN/MAX usage!).
31) For these parameters, the DDR2 SDRAM device is characterized and verified to support tnPARAM = RU{tPARAM / tCK.AVG}, which is in clock
cycles, assuming all input clock jitter specifications are satisfied. For example, the device will support tnRP = RU{tRP / tCK.AVG}, which is in
clock cycles, if all input clock jitter specifications are met. This means: For DDR2–667 5–5–5, of which tRP = 15 ns, the device will support
tnRP = RU{tRP / tCK.AVG} = 5, i.e. as long as the input clock jitter specifications are met, Precharge command at Tm and Active command at
Tm + 5 is valid even if (Tm + 5 - Tm) is less than 15 ns due to input clock jitter.
Rev. 1.0, 2006-11
19
11172006-DXYK-2PPW
