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W9725G6KB25A Datasheet(HTML) 53 Page - Winbond

Part No. W9725G6KB25A
Description  DLL aligns DQ and DQS transitions with clock, Data masks (DM) for write data, Write Data Mask
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Maker  WINBOND [Winbond]
Homepage  http://www.winbond.com
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W9725G6KB25A Datasheet(HTML) 53 Page - Winbond

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W9725G6KB
Publication Release Date: Sep. 03, 2012
- 53 -
Revision A03
31. These parameters are specified per their average values, however it is understood that the following relationship between
the average timing and the absolute instantaneous timing holds at all times. (Min and max of SPEC values are to be used
for calculations in the table below.)
PARAMETER
SYMBOL
MIN
MAX
UNIT
Absolute clock period
tCK(abs)
tCK(avg),min + tJIT(per),min
tCK(avg),max + tJIT(per),max
pS
Absolute clock HIGH pulse width
tCH(abs)
tCH(avg),min x tCK(avg),min +
tJIT(duty),min
tCH(avg),max x tCK(avg),max +
tJIT(duty),max
pS
Absolute clock LOW pulse width
tCL(abs)
tCL(avg),min x tCK(avg),min +
tJIT(duty),min
tCL(avg),max x tCK(avg),max +
tJIT(duty),max
pS
Examples: 1) For DDR2-667, tCH(abs),min = ( 0.48 x 3000 pS ) - 125 pS = 1315 pS
2) For DDR2-1066, tCH(abs),min = ( 0.48 x 1875 pS ) - 75 pS = 825 pS
32. 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;
33. 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 p-channel to n-
channel variation of the output drivers
34. 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.
3) If the system provides tHP of 825 pS into a DDR2-1066 SDRAM, the DRAM provides tQH of 575 pS minimum.
4) If the system provides tHP of 900 pS into a DDR2-1066 SDRAM, the DRAM provides tQH of 650 pS minimum.
35. 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.)
Examples:
1) If the measured jitter into a DDR2-667 SDRAM has tERR(6-10per),min = - 272 pS and tERR(6-10per),max = +
293 pS, then tDQSCK,min(derated) = tDQSCK,min - tERR(6-10per),max = - 400 pS - 293 pS = - 693 pS and
tDQSCK,max(derated) = tDQSCK,max - tERR(6-10per),min = 400 pS + 272 pS = + 672 pS.
Similarly, tLZ(DQ) for DDR2-667 derates to tLZ(DQ),min(derated) = - 900 pS - 293 pS = - 1193 pS and
tLZ(DQ),max(derated) = 450 pS + 272 pS = + 722 pS. (Caution on the min/max usage!)
2) If the measured jitter into a DDR2-1066 SDRAM has tERR(6-10per),min = - 202 pS and tERR(6-10per),max = +
223 pS, then tDQSCK,min(derated) = tDQSCK,min - tERR(6-10per),max = - 300 pS - 223 pS = - 523 pS and
tDQSCK,max(derated) = tDQSCK,max - tERR(6-10per),min = 300 pS + 202 pS = + 502 pS.
Similarly, tLZ(DQ) for DDR2-1066 derates to tLZ(DQ),min(derated) = - 700 pS - 223 pS = - 923 pS and
tLZ(DQ),max(derated) = 350 pS + 202 pS = + 552 pS. (Caution on the min/max usage!)


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