Reference design spins motors in under five minutes

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 new reference design is ideally suited for a wide range of motor control applications including remote control helicopters, motorized toy cars, electronic speed controllers, PC and electric fans, electric tools such as cutters, shears, mowers, nail guns and staplers, and small appliances such as mixers, grinders, toothbrushes and vacuum cleaners.

The complexity of embedded system designs is increasing while development schedules grow tighter. Therefore, reducing development time is a key consideration in MCU selection for motor control applications. Providing cost-effective hardware and production-quality firmware for quick evaluation and deployment in cost-sensitive BLDC applications, the motor control reference design, based on Silicon Labs' C8051F85x/6x MCUs, simplifies the developer’s job. Integrated GUI offers greater flexibility and ease-of-use for developers when controlling and understanding BLDC motor operation, and access to production-ready motor control source code helps to expedite the design-in time..

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

With best-in-class analog performance, small footprint and other features optimized for motor control designs, the C8051F85x/6x family is ideally suited for BLDC applications. Cost-effective, high-performance MCUs based on the 8051, they spin the reference design kit’s 6-pole motor at a maximum speed of 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.

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 power MOSFETs; Turnigy 450 Series 3800 kV BLDC outrunner motor attached to a motor mount board; CD with application notes, production-ready motor control firmware source code and software tools including a motor control GUI; complimentary Keil PK51 development software with unrestricted license (an approximate value of $2,500 USD); and power supply and USB cable.

Diwakar Vishakhadatta, vice president and general manager of 8-bit MCU products at Silicon Labs, comments: “Rapid application development, reduced system cost and fast time to market mean everything to embedded developers working on cost-sensitive motor control designs. We created our sensorless BLDC motor control reference design to help make the developer’s job easier and more productive and to highlight the significant benefits in designing BLDC systems based on our popular C8051F85x/6x MCUs.”

Silicon Labs’ C8051F850-BLDC-RD motor control reference design is available today and priced at $164.99 (USD). Samples and production quantities of Silicon Labs’ C8051F85x/6x MCUs are also available now. MCU pricing in 10,000-unit quantities begins at $0.40 (USD), and high volume pricing starts at $0.30 (USD).