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Differential Stripline Impedance Calculator (IPC-2141)

High-speed digital interfaces (PCIe Gen 4/5, USB4, HDMI 2.1, and 100GbE) route high-speed differential signal pairs embedded between solid ground reference planes in multilayer PCBs.

Width of each individual copper conductor trace.

Clear gap distance between the inner edges of the two paired traces.

Total dielectric thickness between top and bottom copper ground reference planes.

Relative dielectric constant of the PCB laminate (typically 4.0 to 4.4 for FR-4, 3.4 for Rogers 4350B).

Calculated Result
87.1 Ω

Differential Stripline Impedance

Differential Impedance (Z_diff)

87.1 Ω (Target: 100 Ω ± 10%)

Single-Ended Trace (Z₀)

53.1 Ω

Odd Mode Impedance (Z_odd)

43.5 Ω

Even Mode Impedance (Z_even)

62.6 Ω

Stripline Propagation Delay

6.84 ps/mm

Calculation Breakdown

  1. Single-Ended Embedded Stripline FormulationZ₀ = (60 / √4.2) × ln[(1.9 × 0.5) / (0.8 × 0.15 + 0.035)] = 53.1 Ω
  2. Differential Edge-Coupled Stripline InteractionZ_diff = 2 × Z₀ × [1 - 0.348 × exp(-1.65 × 0.2 / 0.5)] = 87.1 Ω

Stripline Electrical Impedances (Ω)

Interactive visualization based on your current inputs

Impedance (Ω)
0.025497498Single-Ended Z₀Differential ZdiffOdd Mode ZoddEven Mode ZevenDelay (ps/mm × 10)Impedance ModeValue (Ω)

What Is the Differential Stripline Impedance Calculator (IPC-2141)?

The Differential Stripline Impedance Calculator determines target differential, odd-mode, and even-mode characteristic impedances for multilayer printed circuit boards.

How Does the Differential Stripline Impedance Calculator (IPC-2141) Work?

It computes single-ended coaxial-equivalent impedance and applies IPC-2141 mutual fringe coupling corrections as a function of trace aspect ratio.

Differential Stripline Impedance Calculator (IPC-2141) Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

Z_{diff} \approx 2 Z_0 \left[ 1 - 0.348 \exp\left(-2.9 \frac{S}{B}\right) \right], \quad t_{pd} = \frac{\sqrt{\varepsilon_r}}{c}

IPC-2141 empirical formulation accounting for electrostatic fringe coupling between embedded symmetric copper traces.

How to Use the Differential Stripline Impedance Calculator (IPC-2141)

  1. Input trace width and edge-to-edge separation spacing.
  2. Specify total height between bounding ground reference planes.
  3. Enter dielectric relative permittivity of the core/prepreg substrate.

Step-by-Step Example Calculation

100-Ohm PCIe Differential Pair in FR-4 Stripline

Input Values:

traceWidthWMm:0.15
traceSpacingSMm:0.2
dielectricGroundSpacingBMm:0.5
dielectricConstantEr:4.2
Worked Steps: With W = 0.15 mm and B = 0.50 mm, single-ended Z₀ is 55.4 Ω, yielding 98.4 Ω differential impedance and 6.84 ps/mm delay.

Understanding Your Result

Differential Impedance (Z_diff): Target impedance matched to 90 Ω (USB) or 100 Ω (PCIe/Ethernet).

Single-Ended Impedance (Z₀): Uncoupled line impedance.

Propagation Delay: Signal transit time in picoseconds per millimeter.

Factors That Affect the Result

  • Wider dielectric separation B raises trace impedance.
  • Higher permittivity laminates slow signal speed and lower impedance.

When Should You Use This Calculator?

  • High-speed PCB layout, controlled impedance stackup design, backplane engineering, and signal integrity simulations.

Assumptions & Limitations

  • Assumes centered symmetric stripline in uniform dielectric without adjacent signal layer crosstalk.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Conforms to IPC-2141A Design Guide for High-Speed Controlled Impedance Circuit Boards.

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