22
12. Trace impedance recommendations
The following table lists the recommended impedance for high-speed signals on the baseboard.
Table12.1
Trace Impedance Recommendation
Signal group
Impedance
PCB manufacture tolerance
All single-ended signal,unless
specified
50 Ohm single-ended
+/-10%
PCIe TX/RX data pair
85 Ohm differential
+/-10%
PCIe differential clocks
100 Ohm differential
+/-10%
USB differential signals
90 Ohm differential
+/-10%
Ethernet Differential signals
100 Ohm differential
+/-10%
MIPI DSI
100 Ohm differential
+/-10%
MIPI CSI
100 Ohm differential
+/-10%
13. High-speed signal trace length compensation
The following table lists the trace length of high-speed signals, including MIPI CSI, MIPI DSI, PCIE, USB
and Giga Ethernet. Those signals are high-speed signals that require the total etched trace lengths to
be equal to each other. Due to space constraints on the SOM, the trace length of those signals
currently are not equal. The designer must incorporate the length difference on the baseboard such
that the trace length for all high-speed signals match each other.
Table13.1
Tr
ace Length Compensation Of SOM
Name
Etch length(mils)
Manhattan length(mils)
MIPI CSI
CSI_CKN
648.69
602.09
CSI_CKP
652.53
634.84
CSI_DN0
660.12
621.78
CSI_DP0
664.04
621.78
CSI_DN1
499.98
464.3
CSI_DP1
504.4
464.31
CSI_DN2
492.11
444.62
CSI_DP2
490.91
477.36
CSI_DN3
639.01
615.15
CSI_DP3
643.82
654.53
MIPI DSI
DSI_CKN
515.05
503.66
DSI_CKP
519.04
503.67
DSI_DN0
510.88
523.35
DSI_DP0
515.6
523.35
DSI_DN1
653.06
661.15
DSI_DP1
657.2
661.15
DSI_DN2
665.93
641.46
DSI_DP2
668.04
641.47
