IS46DR16640C datasheet(31/49 Pages) ISSI

31 / 49 page

Integrated Silicon Solution, Inc. — www.issi.com

Rev. 00A

6/4/2013

IS43/46DR81280C, IS43/46DR16640C

41. 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!)

42. 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!)

43. When the device is operated with input clock jitter, this parameter needs to be derated by { -tJIT(duty),max -

tERR(6-10per),max } and { - tJIT(duty),min - tERR(6-10per),min } of the actual 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 = - 272 ps, tERR(6-10per),max =

+ 293 ps, tJIT(duty),min = - 106 ps and tJIT(duty),max = + 94 ps, then tAOF,min(derated) = tAOF,min + { - tJIT(duty),

max - tERR(6-10per),max } = - 450 ps + { - 94 ps - 293 ps} = - 837 ps and tAOF,max(derated) = tAOF,max + { -

tJIT(duty),min - tERR(6-10per),min } = 1050 ps + { 106 ps + 272 ps } = + 1428 ps. (Caution on the min/max usage!)

44. For tAOFD of DDR2-400/533, the 1/2 clock of tCK in the 2.5 x tCK assumes a tCH, input clock HIGH pulse width

of 0.5 relative to tCK. tAOF,min and tAOF,max should each be derated by the same amount as the actual amount of

tCH offset present at the DRAM input with respect to 0.5. For example, if an input clock has a worst case tCH of 0.45,

the tAOF,min should be derated by subtracting 0.05 x tCK from it, whereas if an input clock has a worst case tCH of

0.55, the tAOF,max should be derated by adding 0.05 x tCK to it. Therefore, we have;

tAOF,min(derated) = tAC,min - [0.5 - Min(0.5, tCH,min)] x tCK

tAOF,max(derated) = tAC,max + 0.6 + [Max(0.5, tCH,max) - 0.5] x tCK

tAOF,min(derated) = Min(tAC,min, tAC,min - [0.5 - tCH,min] x tCK)

tAOF,max(derated) = 0.6 + Max(tAC,max, tAC,max + [tCH,max - 0.5] x tCK)

where tCH,min and tCH,max are the minimum and maximum of tCH actually measured at the DRAM input balls.

45. For tAOFD of DDR2-667/800, the 1/2 clock of nCK in the 2.5 x nCK assumes a tCH(avg), average input clock

HIGH pulse width of 0.5 relative to tCK(avg). tAOF,min and tAOF,max should each be derated by the same amount

as the actual amount of tCH(avg) offset present at the DRAM input with respect to 0.5. For example, if an input clock

has a worst case tCH(avg) of 0.48, the tAOF,min should be derated by subtracting 0.02 x tCK(avg) from it, whereas

if an input clock has a worst case tCH(avg) of 0.52, the tAOF,max should be derated by adding 0.02 x tCK(avg) to it.

Therefore, we have;

tAOF,min(derated) = tAC,min - [0.5 - Min(0.5, tCH(avg),min)] x tCK(avg)

tAOF,max(derated) = tAC,max + 0.6 + [Max(0.5, tCH(avg),max) - 0.5] x tCK(avg)

tAOF,min(derated) = Min(tAC,min, tAC,min - [0.5 - tCH(avg),min] x tCK(avg))

tAOF,max(derated) = 0.6 + Max(tAC,max, tAC,max + [tCH(avg),max - 0.5] x tCK(avg))

where tCH(avg),min and tCH(avg),max are the minimum and maximum of tCH(avg) actually measured at the DRAM

input balls.

Note that these deratings are in addition to the tAOF derating per input clock jitter, i.e. tJIT(duty) and tERR(6-10per).

However tAC values used in the equations shown above are from the timing parameter table and are not derated.

Thus the final derated values for tAOF are;

tAOF,min(derated_final) = tAOF,min(derated) + { - tJIT(duty),max - tERR(6-10per),max }

tAOF,max(derated_final) = tAOF,max(derated) + { - tJIT(duty),min - tERR(6-10per),min }

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