Intel® 31244 PCI-X to Serial ATA Controller
Printed Circuit Board (PCB) Methodology
6.2.2Motherboard Stackup for Backplane Designs
The motherboard is supporting components in addition to GD31244, so an assumption is, desktop PC requirements are dominate to assure the processor and memory subsystem may be implemented with normal 60 ohm guidelines.
Table 12. | Motherboard Stackup, Microstrip |
|
|
| |
|
|
|
|
|
|
| Variable | Nominal (mil) | Tolerance | Min (mil) | Max (mil) |
|
|
|
|
|
|
| Mask Thickness | 0.8 | +/- 0.2 | 0.6 | 1.0 |
|
|
|
|
|
|
| Mask Er | 3.6 |
| 3.6 | 3.6 |
|
|
|
|
|
|
| Trace Height | 4.0 | +/- 0.3 | 3.7 | 4.3 |
|
|
|
|
|
|
| Preg Er | 4.15 | +/- 0.55 | 3.6 | 4.7 |
|
|
|
|
|
|
| Plane Thickness | 1.4 | +/- 0.2 | 1.2 | 1.6 |
|
|
|
|
|
|
| Trace Thickness | 1.4 | +/- 0.4 | 1.0 | 1.8 |
|
|
|
|
|
|
| Trace Width | 5 mil | +/- 1.5 | 3.5 | 6.5 |
|
|
|
|
|
|
| Total Thickness | 62.0 | +/- 6.0 | 56.0 | 68.0 |
|
|
|
|
|
|
Table 13. | Motherboard Microstrip Parameters |
| |
|
|
|
|
| Parameter | Routing Guideline | Notes |
|
|
|
|
| Motherboard Layout | Microstrip |
|
|
|
|
|
| Single Ended Trace Impedance | 55 +/- 12% |
|
|
|
|
|
| Differential Trace Impedance | 100 ohms +/- 15% |
|
|
|
|
|
| Reference Plane | ground |
|
|
|
|
|
| Trace Thickness | 1.4 mil |
|
|
|
|
|
| Trace Width | 5 mil |
|
|
|
|
|
| Intra Pair Trace Spacing | 15 mil | |
|
|
|
|
| 55 mil | pair to pair | |
|
|
|
|
| Trace Length | 2” to 6” |
|
|
|
|
|
| Trace Length Matching | 10 mil | |
|
|
|
|
| Vias | 0 | Minimize number of vias (none preferred). Each |
| channel in the pair has an equal number of vias. | ||
|
|
| |
|
|
|
|
| When possible, it is recommended that the designer use stripline for the following reasons: | ||
•Reduced skin effect relative to microstrip
•Reduced forward cross talk
•Reduced jitter through differential stackup and isolated power delivery
42 | Design Guide |
