Similar to switched power supplies, the motor drive environment is inherently noisy and prone to Electromagnetic Interference (EMI), care must be taken in the PCB design phase. One critical aspect is the treatment of grounding, and layout practices that help minimize impact from grounding parasitics. Component placement and PCB layout play an important role in optimizing a motor drive design.

It is good practice to separate the inverter stage from the rest of the circuitry including the CSA. Grounding planes and power planes should be partitioned to achieve a minimum inductance design. Minimum current loop should be implemented for the switching nodes. Signal traces including those of current sensing should stay clear of the switching nodes. They should not run directly above or below the switching nodes and planes that carry recirculating current. Within the inverter stage, separate grounding islands can be created for each switching node to contain local recirculating current, this goes hand in hand with the goal of minimizing parasitic inductance.

Figure 7-7 is an example of a 48-V BLDC motor driver design with inline shunt based current sensing, it is implemented on a 4-layer PCB. The inverter stage including shunt resistors are located in the lower left part of the board, colored in light blue. The rest of the board is reserved for control circuitry and is located in the area colored yellow. Copper planes are created for power supplies and ground. A smaller ground plane is created for each of the switching nodes. These three smaller areas can be seen highlighted and noted as U, V and W in Figure 7-7. These local ground planes minimize current return loop for the switches and help contain switching noise.