IEEE Solid-State Circuits Magazine - Spring 2016 - 25
and the reference clock, as illustrated
in Figure 5(a).
To compensate for the unpredictable variation in channel flight times,
a source-synchronous clocking architecture was adopted, and two pins
per byte were added, to transmit a
differential, periodic DQS signal in
parallel with the random data (DQ),
as shown in Figure 5(b). Referencing the READ DQ to the DQS signal
mitigated sensitivity to time of flight,
and the phase relationship between
data and the system clock no longer
limited performance. To strobe the
optimum data sampling point during
READ operation, the controller uses
DLL or phase-locked-loop (PLL) to
make a 90° lagged signal. As shown
in Figure 6, at the point of transmission, the WRITE data is center aligned
with the DQS signal while the READ
data is edge aligned with the DQS [8].
This is called a source-synchronous
scheme [9]-[11].
One final early innovation to
decouple I/O speed from the much
slower memory-array cycle time was
the prefetch scheme, through which
the array transfers 2-N bits of data
at a time, where N represents the
number of column accesses. Initially, DDR SDRAM started with a
2-b prefetch scheme to support the
desired I/O operating speed. Since
then, the amount of prefetched data
has grown to support subsequent
increases in effective I/O bandwidth.
To summarize: the combination of
DLL-based tAC compensation, sourcesynchronous DQS, and prefetch
features incorporated into the early
CK
DDR Case
tACPVT1
DataPVT1
tACPVT1
DataPVT2
DataPVT1 + DataPVT2
No Valid Data Window Without DLL
DDR Case
DataPVT1
DataPVT2
DataPVT1 + DataPVT2
Valid Data Window with DLL
Figure 3: High-speed timing sensitivity to PVT variations without and with DLL.
Clock Tree + DLL
Delay
Buffer
PD
Buffer
CK
tD1
DRAM Core
tD1
tD2
tD2
DQ
Buffer
Data Sampler
DRAM Core Control Logic
Data Sampler
Buffer
Figure 4: A simplified DRAM architecture with DLL. PD: phase detector.
CK
CK
DQ
DQ
DQS
DQS
DQ
DQ
tFLT
tFLT
DQ
DQ
Flight time = tFLT′
Flight time = tFLT′
DQS
CK
(a)
Flight time = tFLT′
(b)
Figure 5: A timing diagram (a) without and (b) with DQS.
IEEE SOLID-STATE CIRCUITS MAGAZINE
S P R I N G 2 0 16
25
Table of Contents for the Digital Edition of IEEE Solid-State Circuits Magazine - Spring 2016
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover1
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover2
IEEE Solid-State Circuits Magazine - Spring 2016 - 1
IEEE Solid-State Circuits Magazine - Spring 2016 - 2
IEEE Solid-State Circuits Magazine - Spring 2016 - 3
IEEE Solid-State Circuits Magazine - Spring 2016 - 4
IEEE Solid-State Circuits Magazine - Spring 2016 - 5
IEEE Solid-State Circuits Magazine - Spring 2016 - 6
IEEE Solid-State Circuits Magazine - Spring 2016 - 7
IEEE Solid-State Circuits Magazine - Spring 2016 - 8
IEEE Solid-State Circuits Magazine - Spring 2016 - 9
IEEE Solid-State Circuits Magazine - Spring 2016 - 10
IEEE Solid-State Circuits Magazine - Spring 2016 - 11
IEEE Solid-State Circuits Magazine - Spring 2016 - 12
IEEE Solid-State Circuits Magazine - Spring 2016 - 13
IEEE Solid-State Circuits Magazine - Spring 2016 - 14
IEEE Solid-State Circuits Magazine - Spring 2016 - 15
IEEE Solid-State Circuits Magazine - Spring 2016 - 16
IEEE Solid-State Circuits Magazine - Spring 2016 - 17
IEEE Solid-State Circuits Magazine - Spring 2016 - 18
IEEE Solid-State Circuits Magazine - Spring 2016 - 19
IEEE Solid-State Circuits Magazine - Spring 2016 - 20
IEEE Solid-State Circuits Magazine - Spring 2016 - 21
IEEE Solid-State Circuits Magazine - Spring 2016 - 22
IEEE Solid-State Circuits Magazine - Spring 2016 - 23
IEEE Solid-State Circuits Magazine - Spring 2016 - 24
IEEE Solid-State Circuits Magazine - Spring 2016 - 25
IEEE Solid-State Circuits Magazine - Spring 2016 - 26
IEEE Solid-State Circuits Magazine - Spring 2016 - 27
IEEE Solid-State Circuits Magazine - Spring 2016 - 28
IEEE Solid-State Circuits Magazine - Spring 2016 - 29
IEEE Solid-State Circuits Magazine - Spring 2016 - 30
IEEE Solid-State Circuits Magazine - Spring 2016 - 31
IEEE Solid-State Circuits Magazine - Spring 2016 - 32
IEEE Solid-State Circuits Magazine - Spring 2016 - 33
IEEE Solid-State Circuits Magazine - Spring 2016 - 34
IEEE Solid-State Circuits Magazine - Spring 2016 - 35
IEEE Solid-State Circuits Magazine - Spring 2016 - 36
IEEE Solid-State Circuits Magazine - Spring 2016 - 37
IEEE Solid-State Circuits Magazine - Spring 2016 - 38
IEEE Solid-State Circuits Magazine - Spring 2016 - 39
IEEE Solid-State Circuits Magazine - Spring 2016 - 40
IEEE Solid-State Circuits Magazine - Spring 2016 - 41
IEEE Solid-State Circuits Magazine - Spring 2016 - 42
IEEE Solid-State Circuits Magazine - Spring 2016 - 43
IEEE Solid-State Circuits Magazine - Spring 2016 - 44
IEEE Solid-State Circuits Magazine - Spring 2016 - 45
IEEE Solid-State Circuits Magazine - Spring 2016 - 46
IEEE Solid-State Circuits Magazine - Spring 2016 - 47
IEEE Solid-State Circuits Magazine - Spring 2016 - 48
IEEE Solid-State Circuits Magazine - Spring 2016 - 49
IEEE Solid-State Circuits Magazine - Spring 2016 - 50
IEEE Solid-State Circuits Magazine - Spring 2016 - 51
IEEE Solid-State Circuits Magazine - Spring 2016 - 52
IEEE Solid-State Circuits Magazine - Spring 2016 - 53
IEEE Solid-State Circuits Magazine - Spring 2016 - 54
IEEE Solid-State Circuits Magazine - Spring 2016 - 55
IEEE Solid-State Circuits Magazine - Spring 2016 - 56
IEEE Solid-State Circuits Magazine - Spring 2016 - 57
IEEE Solid-State Circuits Magazine - Spring 2016 - 58
IEEE Solid-State Circuits Magazine - Spring 2016 - 59
IEEE Solid-State Circuits Magazine - Spring 2016 - 60
IEEE Solid-State Circuits Magazine - Spring 2016 - 61
IEEE Solid-State Circuits Magazine - Spring 2016 - 62
IEEE Solid-State Circuits Magazine - Spring 2016 - 63
IEEE Solid-State Circuits Magazine - Spring 2016 - 64
IEEE Solid-State Circuits Magazine - Spring 2016 - 65
IEEE Solid-State Circuits Magazine - Spring 2016 - 66
IEEE Solid-State Circuits Magazine - Spring 2016 - 67
IEEE Solid-State Circuits Magazine - Spring 2016 - 68
IEEE Solid-State Circuits Magazine - Spring 2016 - 69
IEEE Solid-State Circuits Magazine - Spring 2016 - 70
IEEE Solid-State Circuits Magazine - Spring 2016 - 71
IEEE Solid-State Circuits Magazine - Spring 2016 - 72
IEEE Solid-State Circuits Magazine - Spring 2016 - 73
IEEE Solid-State Circuits Magazine - Spring 2016 - 74
IEEE Solid-State Circuits Magazine - Spring 2016 - 75
IEEE Solid-State Circuits Magazine - Spring 2016 - 76
IEEE Solid-State Circuits Magazine - Spring 2016 - 77
IEEE Solid-State Circuits Magazine - Spring 2016 - 78
IEEE Solid-State Circuits Magazine - Spring 2016 - 79
IEEE Solid-State Circuits Magazine - Spring 2016 - 80
IEEE Solid-State Circuits Magazine - Spring 2016 - 81
IEEE Solid-State Circuits Magazine - Spring 2016 - 82
IEEE Solid-State Circuits Magazine - Spring 2016 - 83
IEEE Solid-State Circuits Magazine - Spring 2016 - 84
IEEE Solid-State Circuits Magazine - Spring 2016 - 85
IEEE Solid-State Circuits Magazine - Spring 2016 - 86
IEEE Solid-State Circuits Magazine - Spring 2016 - 87
IEEE Solid-State Circuits Magazine - Spring 2016 - 88
IEEE Solid-State Circuits Magazine - Spring 2016 - 89
IEEE Solid-State Circuits Magazine - Spring 2016 - 90
IEEE Solid-State Circuits Magazine - Spring 2016 - 91
IEEE Solid-State Circuits Magazine - Spring 2016 - 92
IEEE Solid-State Circuits Magazine - Spring 2016 - 93
IEEE Solid-State Circuits Magazine - Spring 2016 - 94
IEEE Solid-State Circuits Magazine - Spring 2016 - 95
IEEE Solid-State Circuits Magazine - Spring 2016 - 96
IEEE Solid-State Circuits Magazine - Spring 2016 - 97
IEEE Solid-State Circuits Magazine - Spring 2016 - 98
IEEE Solid-State Circuits Magazine - Spring 2016 - 99
IEEE Solid-State Circuits Magazine - Spring 2016 - 100
IEEE Solid-State Circuits Magazine - Spring 2016 - 101
IEEE Solid-State Circuits Magazine - Spring 2016 - 102
IEEE Solid-State Circuits Magazine - Spring 2016 - 103
IEEE Solid-State Circuits Magazine - Spring 2016 - 104
IEEE Solid-State Circuits Magazine - Spring 2016 - 105
IEEE Solid-State Circuits Magazine - Spring 2016 - 106
IEEE Solid-State Circuits Magazine - Spring 2016 - 107
IEEE Solid-State Circuits Magazine - Spring 2016 - 108
IEEE Solid-State Circuits Magazine - Spring 2016 - 109
IEEE Solid-State Circuits Magazine - Spring 2016 - 110
IEEE Solid-State Circuits Magazine - Spring 2016 - 111
IEEE Solid-State Circuits Magazine - Spring 2016 - 112
IEEE Solid-State Circuits Magazine - Spring 2016 - 113
IEEE Solid-State Circuits Magazine - Spring 2016 - 114
IEEE Solid-State Circuits Magazine - Spring 2016 - 115
IEEE Solid-State Circuits Magazine - Spring 2016 - 116
IEEE Solid-State Circuits Magazine - Spring 2016 - 117
IEEE Solid-State Circuits Magazine - Spring 2016 - 118
IEEE Solid-State Circuits Magazine - Spring 2016 - 119
IEEE Solid-State Circuits Magazine - Spring 2016 - 120
IEEE Solid-State Circuits Magazine - Spring 2016 - 121
IEEE Solid-State Circuits Magazine - Spring 2016 - 122
IEEE Solid-State Circuits Magazine - Spring 2016 - 123
IEEE Solid-State Circuits Magazine - Spring 2016 - 124
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover3
IEEE Solid-State Circuits Magazine - Spring 2016 - Cover4
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2023
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2022
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2021
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_spring2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_winter2020
https://www.nxtbook.com/nxtbooks/ieee/mssc_fall2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_summer2019
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2019winter
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018fall
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018summer
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018spring
https://www.nxtbook.com/nxtbooks/ieee/mssc_2018winter
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2017
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2016
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2015
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_winter2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_fall2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_summer2014
https://www.nxtbook.com/nxtbooks/ieee/solidstatecircuits_spring2014
https://www.nxtbookmedia.com