With the increasingly complex circuit design,How to ensure the integrity of various signals (especially high-speed signals)That is to ensure signal quality,Become a problem.At this point, the need to use the transmission line theory analysis, the control signal line characteristic impedance matching as the key, not strict impedance control, will lead to considerable signal reflection and signal distortion, resulting in design failure.Common signals, such as PCI bus, PCI-E bus, USB, Ethernet, DDR memory, LVDS signals, etc., require impedance control. Impedance control eventually need to achieve through the PCB design, PCB board technology also put forward higher requirements.
The following will introduce our conventional four-layer board thickness of the laminated structure and some common impedance calculation results, customers in need can be based on the following recommended parameters design impedance line width, spacing:
Outer line width 0.195mm, control single-ended impedance 50 +/- 10% ohms (L1 Ref L2, L4 Ref L3)
Double-sided wire width 0.19mm, wire-to-copper pitch 0.254mm, controlling single-sided coplanar impedance 50 +/- 10% ohms (L1 Ref L2, L4 Ref L3)