PCB Rogowski is selected due to linearity over wide bandwidth and low cost. TI devices solve the design challenges of integration and low sensitivity of the coil.

The coil functions as a differential coil with matching return loops. Distance from the conductor determines Rogowski sensitivity by controlling magnetic field density and loop area. External magnetic fields couple into the signal when loop path mismatch occurs in this differential signal with high gain.

The coil design uses a novel layout to match loop paths while offsetting inner vias. This allows greater loop density. Four interleaved Rogowski coils accomplish this design. Two coils, an outer and inner coil, wind in opposite directions and connect in series. These connect differentially with the other pair wound identically.

This topology provides inductive and capacitive noise rejection while increasing coil density. Traditional winding schemes do not offset vias. This invention uses contributions from TIDA01063 and PCB Rogowski research into winding topologies⁽¹⁾.

Figure 3-2 shows a model of the equivalent circuit.

The Rogowski coil output equals the derivative of the current. For a periodic signal the derivative can be calculated using Equation 1.

This matches the simulated transfer function up to the self-resonance point of the PCB coil. For this small coil the theoretical self-resonance point exceeds 40MHz. See TIDA-010987 and TIDA-01063 for more details about PCB Rogowski design.