Analysis: Examination of the Development Process for a Motor Control Circuit Board
High-Performance Motor Controller Streamlines Automated Systems
In the world of automated systems, a reliable motor controller plays a crucial role, especially in those with more than one axis. One such controller, designed by Sierra Circuits, offers excellent service to these complex systems.
The design of the Sierra Circuits motor control board is based on specific guidelines and measures, primarily focused on controlled impedance traces, high-current handling, component placement, and material selection.
Controlled Impedance Traces
For manufacturer clarity and fine adjustments, controlled impedance traces must have widths distinct from other signal traces. Precise trace widths and spacing depend on the target impedance, which varies by layer and application. Controlled impedance traces often use inner layers (stripline) for better shielding and impedance stability, although microstrip (surface layer) is simpler but more prone to losses.
High-Current Handling
High currents require wider traces or thicker copper layers to reduce resistive losses and avoid overheating. The trace width must be calculated based on the current load and acceptable temperature rise. Short and direct routing is also essential to minimize resistance and inductance. Thermal management is crucial, with thermal reliefs and proper PCB thermal design, including heat sinks or thermal vias near power components.
Component Placement
Power components should be placed physically close to the motor terminals and current sensing components to reduce parasitic inductance and noise. Sensitive signal and control circuitry should be separated from noisy high-current paths to minimize electromagnetic interference and crosstalk. Adequate spacing and clearance should be maintained around high-voltage or high-current components for safety and heat dissipation.
Material Selection
Materials with consistent and known dielectric constants are used to achieve reliable impedance control. High-frequency sections might require advanced laminates like Rogers for improved signal integrity. Thicker copper layers and an optimized layer stack-up are chosen to balance impedance control, mechanical strength, and thermal performance.
The Sierra Circuits motor control board is primarily used in the automotive and industrial sectors. It can be found in various propulsion systems such as electric bikes, electric cars, fuel pumps, and motorbikes. The design includes CAN Bus interfacing and is an IPC class-3 design, requiring a thorough inspection for high quality. The board operates with a 50 MHz operating frequency and 100 Mb/S ethernet, and over a thousand components are included in this design.
The board operates on a peak current of 30 amps and an average current of 20 amps, and the motor control board is an 8-layered board with dimensions of 192 mm x 141 mm. Component placement was challenging due to the high number of components and fixed input connector locations. Components are grouped according to their functions to prevent interference.
The motor controller is the brain of electric vehicles, managing energy flow, speed, and direction. In the board, high-current traces are split into different layers to prevent overload issues. The design includes a brushed DC motor controller and is used in servo motors, high-speed tape recorders, X-Y recorders, heavy-duty drives, and optical position encoders in stepper motors. The board incorporates the material FR-370 HR for maximum thermal performance and reliability.
In summary, these measures ensure reliable signal integrity, effective current handling, and robust thermal and mechanical performance for high-current motor control PCBs as illustrated in the Sierra Circuits design approach.
The Sierra Circuits motor control board, designed for complex automated systems, employs controlled impedance traces technology for fine adjustments and manufacturer clarity. This board, primarily used in the automotive and industrial sectors, also incorporates technology that enables high-current handling for improved performance and thermal management.
