１０２
2.12.3 I2C Trace Length Guidelines
Figure 31
: Topology for I2C
Table 36
: I2C Trace Length Guidelines
Parameter
Main Route Guidelines
Notes
Signal Group
I2C
Single End
50Ω ±15%
Nominal Trace Space within I2C
Signal Group
Min. 10mils
Spacing to Other Signal Group
Min. 10mils
LA
Please see the SOM-5992 Layout Checklist
LB
Carrier Board Length
Max length of LA+LB
ASPA
Length Mismatch
NA
Via Usage
Try to minimize number of vias
Notes:
2.12.4 Connectivity Considerations
The maximum amount of capacitance allowed on the Carrier General Purpose I2C bus lines (I2C_DAT,
I2C_CK) is specified by Advantech’s Module. The Carrier designer is responsible for ensuring that the
maximum amount of capacitance is not exceeded and the rise/fall times of the signals meet the I2C bus
specification. As a general guideline, an IC input has 8pF of capacitance, and a PCB trace has 3.8pF per
inch of trace length.
