HYB18T512400B2C Datasheet, PDF (57/69 Pages) Qimonda AG – 512-Mbit Double-Data-Rate-Two SDRAM

Internet Data Sheet
HY[B/I]18T512[40/80/16]0B2[C/F](L)
512-Mbit Double-Data-Rate-Two SDRAM
7.3
Jitter Definition and Clock Jitter Specification
Generally, jitter is defined as “the short-term variation of a signal with respect to its ideal position in time”. The following table
provides an overview of the terminology.
Symbol
t_CK.AVG
TABLE 49
Average Clock and Jitter Symbols and Definition
Parameter
Description
Units
Average clock period t_CK.AVG is calculated as the average clock period within any consecutive ps
200-cycle window:
t_JIT.PER
t_JIT(PER, LCK)
t_JIT.CC
t_JIT(CC, LCK)
t_ERR.2PER
tCK.AVG
=
N-1--
⎛
.^⎜
⎜
N
∑
⎞
tCK_{j⎟⎟}
(1)
⎝_{j = 1}
⎠
Clock-period jitter
N = 200
t_JIT.PER is defined as the largest deviation of any single t_CK from t_CK.AVG: ps
t_JIT.PER = Min/Max of {t_CKi – t_CK.AVG} where i = 1 to 200
Clock-period jitter
during DLL-locking
period
Cycle-to-cycle clock
period jitter
t_JIT.PER defines the single-period jitter when the DLL is already locked.
t_JIT.PER is not guaranteed through final production testing.
t_JIT(PER,LCK) uses the same definition as t_JIT.PER, during the DLL-locking ps
period only.
t_JIT(PER,LCK) is not guaranteed through final production testing.
t_JIT.CC is defined as the absolute difference in clock period between two ps
consecutive clock cycles:
t_JIT.CC = Max of ABS{t_CKi+1 – t_CKi}
Cycle-to-cycle clock
period jitter during
DLL-locking period
Cumulative error
across 2 cycles
t_JIT.CC defines the cycle- to- cycle jitter when the DLL is already locked.
t_JIT.CC is not guaranteed through final production testing.
t_JIT(CC,LCK) uses the same definition as t_JIT.CC during the DLL-locking ps
period only.
t_JIT(CC,LCK) is not guaranteed through final production testing.
t_ERR.2PER is defined as the cumulative error across 2 consecutive cycles ps
from t_CK.AVG:
⎛^{i + n – 1}
⎞
tERR(2per)
=
⎜
⎜
∑
tCK_{j⎟⎟} – n × tCK(avg)
(2)
⎝ _j=i
⎠
n = 2 for t_ERR(2per)
where i = 1 to 200
Rev. 1.12, 2007-05
57
10062006-YPTZ-CDR7