PCM-072/phyCORE-AM64xx System on Module
L-860e.A0
© PHYTEC America L.L.C. 2022
34
Vias and Stubs
•
Avoid routing through vias when possible. The number of vias on the differential pairs should be minimized. If
necessary, each signal of the differential pair should be routed through matching number of vias. In the case of
multiple differential lanes in the same interface, all lines should have the same number of vias.
•
Minimize discontinuities on the signal path (such as stubs) and avoid placing test points, external components like
0Ω resistors, or any other components that are not required when possible.
•
Surface-mount receptacles are preferred over through-hole connectors, as signals can be routed on the top layer
of the PCB without introducing vias to the signal path. If through-hole pins are necessary, it may be beneficial to
route signals on the bottom layer.
4.11.2 General Signal Routing Guidelines
•
Pay special attention to signal placement, trace impedances, maximum trace length, and trace length tolerances
when routing SOM signals.
•
Place and route high-speed signals, such as USB3.0, PCIe, Ethernet, etc. before placing and routing any other
interfaces. This is recommended to ensure that the stricter trace lengths and length matching requirements of
these interfaces are met.
•
Place and route the remaining interfaces after the high-speed interfaces are completely routed.
•
All communication signals/interfaces should have an accompanying solid reference plane.
•
Separate clocks and other high-speed signals as much as possible from nearby traces to reduce crosstalk. A
general rule is to use a clearance of at least 3 times the trace width.
5
Power
The following sub-sections discuss the power configuration of the phyCORE-AM64xx in detail.
relationships between the voltage rails and the devices on the phyCORE-AM64xx SOM.
Table 12 External Supply Voltages
Signal
Direction
Power Draw / Deliver
Pins
Description
VIN
I
Draw 10W (2A)
1
A1, A2, A3
5.0V Main Power Supply
VBAT
I
Draw 120 nW (40nA)
B4
Backup Power for RTC
VDDSHV_SD_IO
O
None
B3
This rail can be used as a pullup
voltage for the SD/MMC1 signals.
However, since the MMC1 signals
have internal pullups, this rail can be
left disconnected.
VDD_3V3_OUT
O
Deliver 6.6W (2A)
B1, B2
3.3V voltage source for external
circuity. VDD_3V3_OUT goes high
after the SOM voltages have
stabilized and X_PGOOD goes high.
GND
O
None
A4, A5, A10, A15, A20, A23,
A26, A29, A35, A40, A45, A50, Ground
