Nvidia JETSON TX2 - Page 92

NVIDIA Jetson TX2/TX2i OEM Product Design Guide
JETSON TX2/TX2i OEM PRODUCT | DESIGN GUIDE | 20180618 92
Figure 53. Transmission Line Height
▪ Transmission line return current:
- High-speed return current follows the path of least inductance.
- The low est inductance path for a transmission line is the portion of the line closest to the dielectric surface;
i(D) is proportional to
1
(1 +
D
H
2
)
▪ Crosstalk on solid reference plane (Figure 54):
- Crosstalk is caused by the mutual inductance of tw o parallel traces.
- Crosstalk at the second trace is proportional to
1
(1 +
D
H
2
)
- The signals need to be properly spaced to minimize crosstalk.
Figure 54. Crosstalk on Reference Plane
▪ Reference plane selection
- Solid ground is preferred as reference plane.
- Solid pow er can be used as reference plane with decoupling capacitors near driver and receiver.
- Reference plane cuts and layer changes need to be avoided.
▪ Pow er plane cut example (Figure 55)
- Pow er plane cuts w ill cause EMI issues.
- Pow er plane cuts also induce crosstalk to adjacent signals.
Figure 55. Example of Power Plane Cuts
▪ When cut is unavoidable:
- • Place decoupling capacitors near transition.
- • Place transition near source or receiver w hen decoupling capacitors are abundant (Figure 56).