The control signals to the LMG341xR070 must be protected from the high dv/dt that the GaN power stage produces. Coupling between the control signals and the drain may cause circuit instability and potential destruction. Route the control signals (IN, FAULT and LPM) over a ground plane located on an adjacent layer. For example, in the layout in Figure 19, all the signals are routed on the top layer directly over the signal GND plane on the first inner copper layer.
The signals for the high-side device are often particularly vulnerable. Coupling between these signals and system ground planes could cause issues in the circuit. Keep the traces associated with the control signals away from drain copper. For the high-side level shifter, ensure no copper from either the input or output side extends beneath the isolator or the device's CMTI may be compromised.