WED3EG7218S-JD3
White Electronic Designs
PRELIMINARY
DDR SDRAM COMPONENT ELECTRICAL CHARACTERISTICS AND
RECOMMENDED AC OPERATING CONDITIONS (continued)
DDR400: VCC = VCCQ = +2.6V ± 0.1V; DDR333, 266, 200: VCC = VCCQ = +2.5V ± 0.2V
AC Characteristics
403
335
262/265
202
Parameter
Symbol Min
Max
Min
15
Max
Min
Max
Min
20
Max
Units Notes
ACTIVE to READ or WRITE delay
PRECHARGE command period
DQS read preamble
tRCD
tRP
15
15
0.9
0.4
10
0.25
0
15
15
0.9
0.4
15
0.25
0
ns
ns
15
20
tRPRE
tRPST
tRRD
1.1
0.6
0.9
0.4
12
1.1
0.6
1.1
0.6
0.9
0.4
15
1.1
0.6
tCK
tCK
ns
DQS read postamble
ACTIVE bank a to ACTIVE bank b command
DQS write preamble
tWPRE
tWPRES
tWPST
tWR
0.25
0
0.25
0
tCK
DQS write preamble setup time
DQS write postamble
ns
tCK
ns
tCK
ns
μs
μs
ns
ns
tCK
10,11
9
0.4
15
2
0.6
0.4
15
0.6
0.4
15
1
0.6
0.4
15
0.6
Write recovery time
Internal WRITE to READ command delay
Data valid output window
tWTR
NA
1
1
tQH-tDQSQ
70.3
7.8
tQH-tDQSQ
70.3
7.8
tQH-tDQSQ
tQH-tDQSQ
70.3
7.8
13
12
12
REFRESH to REFRESH command interval
Average periodic refresh interval
Terminating voltage delay to VCC
Exit SELF REFRESH to non-READ command
Exit SELF REFRESH to READ command
tREFC
tREFI
tVTD
70.3
7.8
0
0
0
0
tXSNR
tXSRD
70
75
75
75
200
200
200
200
June 2006
Rev. 2
8
White Electronic Designs Corporation • (602) 437-1520 • www.wedc.com
WEDC [ WHITE ELECTRONIC DESIGNS CORPORATION ]
