EDE1104ACSE, EDE1108ACSE, EDE1116ACSE
6. 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;
7. tQHS accounts for:
a. 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
b. 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 p-channel to n-channel variation of the output drivers.
8. 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:
a. If the system provides tHP of 1315ps into a DDR2-667 SDRAM, the DRAM provides tQH of 975ps
(min.)
b. If the system provides tHP of 1420ps into a DDR2-667 SDRAM, the DRAM provides tQH of 1080ps
(min.)
9. RU stands for round up. WR refers to the tWR parameter stored in the MRS.
10. When the device is operated with input clock jitter, this parameter needs to be derated by the actual
tERR(6-10per) 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 tERR(6-10per) min. = −272ps and
tERR(6-10per) max. = +293ps, then tDQSCK min.(derated) = tDQSCK min. − tERR(6-10per) max. =
−400ps − 293ps = −693ps and tDQSCK max.(derated) = tDQSCK max. − tERR(6-10per) min. = 400ps +
272ps = +672ps. Similarly, tLZ(DQ) for DDR2-667 derates to tLZ(DQ) min.(derated) = −900ps − 293ps =
−1193ps and tLZ(DQ) max.(derated)= 450ps + 272ps = +722ps.
11. 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. = −72ps and
tJIT(per) max. = +93ps, then tRPRE min.(derated) = tRPRE min. + tJIT(per) min. = 0.9 × tCK(avg) − 72ps
= +2178ps and tRPRE max.(derated) = tRPRE max. + tJIT(per) max. = 1.1 × tCK(avg) + 93ps = +2843ps.
12. 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. = −72ps and
tJIT(duty) max. = +93ps, then tRPST min.(derated) = tRPST min. + tJIT(duty) min. = 0.4 × tCK(avg) −
72ps = +928ps and tRPST max.(derated) = tRPST max. + tJIT(duty) max. = 0.6 × tCK(avg) + 93ps =
+1592ps.
13. Refer to the Clock Jitter table.
14. tWTR is at least two clocks (2 × tCK or 2 × nCK) independent of operation frequency.
Data Sheet E0975E50 (Ver.5.0)
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ELPIDA [ ELPIDA MEMORY ]
