K4T51043QE Datasheet, PDF (40/45 Pages) Samsung semiconductor – 512Mb E-die DDR2 SDRAM Specification

K4T51043QE
K4T51083QE
K4T51163QE
DDR2 SDRAM
10. The maximum limit for this parameter is not a device limit. The device will operate with a greater value for this parameter, but system performance
(bus turnaround) will degrade accordingly.
11. MIN ( tCL, tCH) refers to the smaller of the actual clock LOW time and the actual clock HIGH time as provided to the device (i.e. this value can be
greater than the minimum specification limits for tCL and tCH). For example, tCL and tCH are = 50% of the period, less the half period jitter ( tJIT(HP))
of the clock source, and less the half period jitter due to crosstalk ( tJIT(crosstalk)) into the clock traces.
12. tQH = tHP - tQHS, where :
tHP = minimum half clock period for any given cycle and is defined by clock HIGH or clock LOW (tCH, tCL).
tQHS accounts for:
1) The pulse duration distortion of on-chip clock circuits; 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, separately, due
to data pin skew and output pattern effects, and p-channel to n-channel variation of the output drivers.
13. 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.
14. tDAL = 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 DDR533 at tCK = 3.75ns with WR programmed to 4 clocks.
tDAL = 4 + (15 ns / 3.75 ns) clocks = 4 + (4) clocks = 8 clocks.
15. The clock frequency is allowed to change during self refresh mode or precharge power-down mode.
16. ODT turn on time min is when the device leaves high impedance and ODT resistance begins to turn on. ODT turn on time max is when the ODT
resistance is fully on. Both are measured from tAOND, which is interpreted differently per speed bin. For DDR2-400/533, tAOND is 10 ns (= 2 x 5 ns)
after the clock edge that registered a first ODT HIGH if tCK = 5 ns. For DDR2-667/800, tAOND is 2 clock cycles after the clock edge that registered a
first ODT HIGH counting the actual input clock edges.
17. ODT turn off time min is when the device starts to turn off ODT resistance. ODT turn off time max is when the bus is in high impedance. Both are mea-
sured from tAOFD, which is interpreted differently per speed bin. For DDR2-400/533, tAOFD is 12.5 ns (= 2.5 x 5 ns) after the clock edge that regis-
tered a first ODT LOW if tCK = 5 ns. For DDR2-667/800, if tCK(avg) = 3 ns is assumed, tAOFD is 1.5 ns (= 0.5 x 3 ns) after the second trailing clock
edge counting from the clock edge that registered a first ODT LOW and by counting the actual input clock edges.
18. 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) . Figure 17 shows a method to calculate the point when device is no
longer driving (tHZ), or beginsdriving (tLZ) by measuring the signal at two different voltages. The actual voltage measurement points are not critical as
long as the calculation is consistent. tLZ(DQ) refers to tLZ of the DQS and tLZ(DQS) refers to tLZ of the (U/L/R)DQS and (U/L/R)DQS each treated as
single-ended signal.
19. 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 17 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 consis-
tent.
tHZ
tRPST end point
T2
T1
VOH + x mV
VOH + 2x mV
VOL + 2x mV
VOL + x mV
tHZ,tRPST end point = 2*T1-T2
VTT + 2x mV
VTT + x mV
VTT - x mV
VTT - 2x mV
T1
T2
tLZ
tRPRE begin point
tLZ,tRPRE begin point = 2*T1-T2
Figure 17 - Method for calculating transitions and endpoints
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Rev. 1.8 July 2007