Internet Data Sheet
HYS[64/72]T[32/64/128]xx0HU-[25F/2.5/3/3S/3.7/5]-B
Unbuffered DDR2 SDRAM Module
28) 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 3 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 consistent.
29) 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!).
30) 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!).
31) For these parameters, the DDR2 SDRAM device is characterized and verified to support tnPARAM = RU{tPARAM / tCK.AVG}, 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 DDR2–667 5–5–5, of which tRP = 15 ns, the device will support
tnRP = RU{tRP / tCK.AVG} = 5, i.e. as long as the input clock jitter specifications are met, Precharge command at Tm and Active command at
Tm + 5 is valid even if (Tm + 5 - Tm) is less than 15 ns due to input clock jitter.
32) tWTR is at lease two clocks (2 x tCK) independent of operation frequency.
Rev. 1.3, 2006-12
26
03292006-6GMD-RSFT
QIMONDA [ QIMONDA AG ]
