IS43/46TR16640B, IS43/46TR16640BL
IS43/46TR81280B, IS43/46TR81280BL
Integrated Silicon Solution, Inc. – www.issi.com – 69
Rev. I1
02/14/2018
9.4 Timing Notes
9.4.1 Jitter
Specific Note a
Unit “tCK(avg)” represents the actual tCK(avg) of the input clock under operation. Unit “nCK” represents one clock cycle of
the input clock, counting the actual clock edges. ex) tMRD=4 [nCK] means; if one Mode Register Set command is
registered at Tm, another Mode Register Set command may be registered at Tm+4, even if (Tm+4-Tm) is 4 x tCK(avg) +
tERR(4per), min.
Specific Note b
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.
Specific Note c
These parameters are measured from a data strobe signal (DQS(L/U), DQS(L/U)) 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.
Specific Note d
These parameters are measured from a data signal (DM(L/U), DQ(L/U)0, DQ(L/U)1, etc.) transition edge to its respective
data strobe signal (DQS(L/U), DQS(L/U)) crossing.
Specific Note e
For these parameters, the DDR3 SDRAM device supports tnPARAM [nCK] = RU{tPARAM[ns] / tCK(avg)[ns]}, 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 DDR3-800 6-6-
6, of which tRP = 15ns, the device will support tnRP = RU{tRP/tCK(avg)} = 6, as long as the input clock jitter specifications
are met, i.e. Precharge command at Tm and Active command at Tm+6 is valid even if (Tm+6-Tm) is less than 15ns due to
input clock jitter.
Specific Note f
When the device is operated with input clock jitter, this parameter needs to be derated by the actual tERR(mper), act of
the input clock, where 2 <= m <=12. (output derating are relative to the SDRAM input clock.)
For example, if the measured jitter into a DDR3-800 SDRAM has tERR(mper),act,min = -172ps and tERR(mper),act,max
= 193ps, then tDQSCK,min(derated) = tDQSCK,min - tERR(mper),act,max = -400ps - 193ps = -593ps and
tDQSCK,max(derated) = tDQSCK,max - ERR(mper),act,min = 400ps + 172ps = 572ps. Similarly, tLZ(DQ) for DDR3-800
derates to tLZ(DQ),min(derated) = -800ps - 193ps = -993ps and tLZ(DQ),max(derated) = 400ps + 172ps = 572ps.
(Caution on the min/max usage!)
Note that tERR(mper),act,min is the minimum measured value of tERR(nper) where 2 <= n <= 12, and
tERR(mper),act,max is the maximum measured value of tERR(nper) where 2 <= n <= 12.
Specific Note g
When the device is operated with input clock jitter, this parameter needs to be derated by the actual tJIT(per),act of the
input clock. (output deratings are relative to the SDRAM input clock.) For example, if the measured jitter into a DDR3-800
SDRAM has tCK(avg),act=2500ps, tJIT(per),act,min = -72ps and tJIT(per),act,max = 93ps, then tRPRE,min(derated) =
tRPRE,min + tJIT(per),act,min = 0.9 x tCK(avg),act + tJIT(per),act,min = 0.9 x 2500ps - 72ps = 2178ps. Similarly,
tQH,min(derated) = tQH,min + tJIT(per),act,min = 0.38 x tCK(avg),act + tJIT(per),act,min = 0.38 x 2500ps - 72ps = 878ps.
(Caution on the min/max usage!)