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Virtex-5 FPGA ML561 User Guide www.xilinx.com 81
UG199 (v1.2) April 19, 2008
Signal Integrity Correlation Results
R
QDRII Write Operation
This subsection shows the test results for the QDR2_D_BY0_B5 signal from FPGA3 (U34)
to QDRII memory (U35) measured at 300 MHz (600 Mb/s), where the unit interval
(UI) = 167 ns.
Figure 7-39: Post-Layout IBIS Schematics of QDRII Write Data Bit (QDR2_D_BY0_B5)
K7R323684M_1.8V
D5
C7
500.0 fF
58.1 fF
399.1 fF
177.3 fF
22.9 fF
22.9 fF22.9 fF
U35.G11
28.5 ohms
4.404 ps
0.027 in
QDR2_D_BY0_B5
49.0 ohms
11.902 ps
0.079 in
QDR2_D_BY0_B5
49.8 ohms
520.665 ps
3.333 in
QDR2_D_BY0_B5
28.5 ohms
4.473 ps
0.028 in
QDR2_D_BY0_B5
Virtex-5 FPGA
QDR2_D_BY0_B5
U34.M31
UG199_c7_39_070907
49.0 ohms
5.283 ps
0.035 in
QDR2_D_BY0_B5
71.0 ohms
27.482 ps
AutoPadstk_3
45.1 ohms
7.862 ps
AutoPadstk_19
70.8 ohms
16.339 ps
AutoPadstk_3
TL2 TL4 TL5
TL6
TL7 TL8 TL3 TL1
QDR2_D... QDR2_D... QDR2_D...
QDR2_D...
QDR2_D...
QDR2_D...
R1586
VCC0V7…
0.9V
49.9 ohms
Table 7-11: Circuit Elements of QDRII Write Data bit (QDR2_D_BY0_B5)
Element Designation Description
Driver U34.M31 FPGA HSTL_I_18
Receiver U35.G11 QDRII memory
Probe Point C7 Via under Memory
PCB Termination R1586 External termination at memory
Trace Length TL 2, 5, 8, 1 3.46 inches
Table 7-12: QDRII Write Operation Correlation Results
Measurement
DVW
(% UI)
ISI
(% UI)
Noise Margin
(VIH + VIL) = Total
(% of VREF)
Overshoot / Undershoot
Margin
(% of VREF)
Hardware at probe
point
1.40 ns
(84.1%)
(50 + 70) = 120 ps (7.2%)
(340 + 400) = 740 mV
(82.2%)
(450 + 400) = 850 mV
(94.5%)
Simulation correlation
slow-weak corner
1.39 ns
(83.5%)
(136 + 91) = 227 ps (13.6%)
(344 + 398) = 742 mV
(82.5%)
(483 + 452) = 935 mV
(103.9%)
Correlation Delta:
HW vs. Simulation
10 ps
(0.6%)
107 ps (6.4%) 2 mV (0.3%) 85 mV (9.4%)
Extrapolation at IOB
slow-weak corner
1.38 ns
(83%)
(172 + 141) = 313 ps
(18.8%)
(329 + 358) = 687 mV
(76.3%)
(400 + 361) = 761 mV
(84.5%)
Extrapolation at IOB
fast-strong corner
1.49 ns
(89%)
(126 + 91) = 217 ps (13.0%)
(353 + 376) = 729 mV
(81.0%)
(156 + 30) = 186 mV
(20.7%)