Characteristic impedance
70.67 Ω
Effective dielectric 2.977, delay 0.15 ns/in
Differential
124.57 Ω
Gap 0.15 mm
Impedance
Dial in controlled-impedance traces with visuals, not guesswork.
Uses Hammerstad/Jensen approximations plus FR-4 stack presets to mirror DigiKey’s trace calculator while adding a green solder-mask cross-section so geometry is obvious.
70.67 Ω
Z0
2.977
εeff
0.15 ns/in
Delay
Common stacks
Start with a preset, then tweak widths or dielectric constants to match your fab’s stack drawing.
Inputs
Units
Set to 0 for single-ended focus.
Quick targets
Target 50 Ω
20.67 Ω off
Adjust width or dielectric to zero this delta.
Target 75 Ω
4.33 Ω off
Adjust width or dielectric to zero this delta.
Target 90 Ω
19.33 Ω off
Adjust width or dielectric to zero this delta.
Signal integrity cues
Use the graph to explain trace geometry to non-layout teammates—green mask and copper stack mirror what arrives from fab.
Stack alignment
Swap presets to compare outer-layer microstrip vs. inner stripline results before asking your CM for custom builds.
Design notes
- Hammerstad/Jensen aligns with Digi-Key’s impedance calculator; always cross-check against your fab’s field solver before tape-out.
- Solder mask slows microstrip/coplanar edges; if your fab uses LPI mask, ask for the actual cured thickness and update the input.
- Differential impedance drifts with coupling—tighten pair gaps or raise copper thickness to stabilize around 90 Ω.
- Unit toggle keeps documentation simple; stay in mils when copying dimensions into fab drawings, switch back to mm for stack tables.