PCB Differential Pair Calculator

Importance of Differential Pair Design

In high-speed PCB design, differential pairs are crucial for reducing electromagnetic interference and improving signal integrity. Good differential pair design can:

  • Reduce common-mode noise
  • Improve signal transmission quality
  • Enhance system EMI immunity
  • Optimize high-speed signal performance

Design Guidelines

Spacing Rules

  • Keep spacing consistent throughout the trace length
  • Typical spacing: 2x to 4x trace width
  • Maintain minimum spacing per manufacturer specs

Length Matching

  • Match lengths within 5-10 mils
  • Use serpentine routing for length matching
  • Avoid acute angles in serpentine patterns

Common Applications

  • High-speed digital interfaces (USB, HDMI, PCIe)
  • Memory interfaces (DDR)
  • Network communications (Ethernet)
  • LVDS signaling

Notes on Calculations

  • Results are based on 2D field solver approximations
  • Consider manufacturing tolerances in your design
  • Verify critical designs with advanced simulation tools
  • Account for material property variations

Reference Values

Material Dielectric Constant (Er)
FR4 4.0 - 4.5
Rogers RO4350B 3.48
PTFE 2.1 - 2.5