Reference design gets motors spinning in less than five minutes -

Reference design gets motors spinning in less than five minutes


Silicon Labs has introduced a brushless dc (BLDC) motor control reference design featuring ready-to-use hardware and software for sensorless BLDC applications using Silicon Labs’ C8051F85x/6x microcontrollers (MCUs). The new reference design provides a comprehensive, system-level solution that accelerates embedded development 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 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 targeted for BLDC applications because of its best-in-class analog performance, small footprint, and other features optimized for motor control designs. The cost-effective, high-performance 8051-based MCU spins 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)
  • Power supply and USB cable

For additional information about the sensorless BLDC motor control reference design, to order MCU samples, and to download complimentary Keil development tools, please visit .

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