Microstrip and Stripline Skew

Two common methods to route high-speed lines are stripline, which sandwiches the signal line between ground planes, and microstrip, which lays the signal line on the board's surface. Efinix® recommends using stripline because it provides a better SNR for high-speed signals and helps to reduce skew.

Figure 1. Comparing Microstrip and Stripline Design

Skew is the timing delay difference between 2 or more signals. The following table shows skew control recommendations for double data rate and single data rate domains for various operating frequencies, as well as the recommended PCB skew for CK to DQS timing.

Note: The timing information provided here is for reference only. The layout, PCB, and components you use will affect the actual signal timing and skew.

Table 1. Skew Control Recommendations
Speed (Bit Rate)		2400 Mbps LPDDR4	Unit
DQ to DQS	Max Skew	75	ps
CK to DQS	Max Skew	350	ps
A, CKE, CE to CK	Max Skew	100	ps