Reference design promises quick-start on motor control designs

November 08, 2013 // By Graham Prophet
Silicon Labs has introduced a brushless dc (BLDC) motor control reference design featuring ready-to-use hardware and software for sensorless BLDC applications using its C8051F85x/6x microcontrollers (MCUs).

Silicon Labs believes that reducing development time is a key consideration in MCU selection for motor control applications. The C8051F85x/6x MCU-based motor control reference design, the company says, makes your easier by providing cost-effective hardware and production-quality firmware for quick evaluation and deployment in cost-sensitive BLDC applications. The motor control graphical user interface (GUI) gives developers greater flexibility and ease-of-use when controlling and understanding BLDC motor operation, and access to production-ready motor control source code helps to expedite the design-in time.

The sensorless BLDC motor control reference design uses a C8051F850 MCU to control a BLDC outrunner motor (typically found in toy helicopters) mounted on the motor mount board. The powertrain board contains gate drivers, power MOSFETs, a current sensing resistor as well as resistor dividers to attenuate motor phase voltages so that they can be measured by the C8051F85x/6x MCU. The MCU board contains a C8051F85x/6x MCU, as well as buttons to start/stop and change motor direction and reset the MCU. The MCU’s PWM output drives the gate drivers on the powertrain board. The MCU board also contains an operational amplifier (op-amp) to amplify the current sensing voltage so it can be measured by the MCU.

The C8051F85x/6x family is suited to BLDC applications because of its analogue performance, and small footprint, Silabs asserts. The reference design kit’s 6-pole motor spins at up to 50,000 rpm. The C8051F85x/6x MCU family also helps developers reduce overall system cost by eliminating the need for external components such as a crystal oscillator, voltage reference, level shifters, temperature sensor and other discretes.

Silicon Labs’ sensorless BLDC reference design is designed to give developers a productive, comprehensive “out-of-box” experience, providing everything needed to get a motor spinning in less than five minutes. The reference design includes the following hardware and software tools:

• C8051F850 MCU control board providing the intelligence to drive the motor and associated peripherals

• Powertrain board with gate drivers and