SLLA500 December   2020 TUSB2E22

 

  1.   Trademarks
  2. 1Introduction to the Embedded USB2 (eUSB2) Physical Layer Supplement
  3. 2eUSB2 Electrical Specifications
  4. 3eUSB2 Trace Routing
  5. 4Matched Trace Length and Skew for eUSB2
  6. 5PCB Stackup for eUSB2 Applications
  7. 6Environmental Concerns and eUSB2
  8. 7References

5 PCB Stackup for eUSB2 Applications

Since eUSB2 supports the same maximum signaling speed as USB 2.0 at 480 Mbps, the PCB stackup requirements are similar. To maintain signal integrity and reduce EMI, a 4-layer PCB or greater is recommended. FR4 is a suitable and affordable material for both eUSB2 and USB 2.0 PCBs with low insertion loss at the Nyquist frequency of 240 MHz of less than 0.1 dB per inch.

Figure 5-1 shows an example PCB stackup with trace routing on layer 1, ground on layer 2, power on layer 3 and trace routing on layer 4. This stack-up assumes eUSB2 and USB differential microstrip routing on the outer layers.

GUID-20201110-CA0I-QBPR-9BZ7-DTKNKKLSHQZX-low.png Figure 5-1 Sample 4-Layer PCB Stackup

Referencing the channel specifications from Table 7-6 in the eUSB2 Physical Layer Supplement, duplicated in Table 5-1, FR4 is adequate for most eUSB2 applications.

Table 5-1 eUSB2 Channel Specification (Informative)
ParameterMaxUnits
Host-to-repeater insertion loss(1) (2)–1.2dB
Repeater-to-connector insertion loss–2dB
(1) The number is specified at 240 MHz frequency.
(2) See Figure 3-1: Repeater Mode Channel Topology for the topology setup.