85
2.9.3 SATA Trace Length Guidelines
Figure 25
: Topology for SATA
Table 29
: SATA Trace Length Guidelines
Parameter
Main Route Guidelines
Notes
Signal Group
SATA
Differential Impedance Target
85 Ω ±10%
Single End
50~55Ω ±15%
Signal length available for the
COM Express Carrier Board
3 inches, a redriver may be necessary for GEN3
signaling rates
Spacing between RX and TX
pairs (inter-pair) (s)
9H
(MS) and
7H
(DS)
1
Spacing between differential
pairs and high-speed periodic
signals
9H
(MS) and
7H
(DS)
1
Spacing between differential
pairs and low-speed non
periodic signals
9H
(MS) and
7H
(DS)
1
LA
Please see the SOM-5992 Layout Checklist
LB
Carrier Board Length
Max length of LA+LB
Support Gen3 : “2~5”
Length matching
Differential pairs (intra-pair): Max.
±5 mils
Reference Plane
GND referencing preferred
Spacing from edge of plane
Min. 40mils
Carrier Board Via Usage
A maximum of 2 vias is recommended.
AC Coupling capacitors
The AC coupling capacitors for the TX and RX lines are
incorporated on the COM Express Module.
Notes:
1.H is height above reference plane.