Simple Development Of Cordless Power Tools With Plug-and-Play Boards

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The boards can also be used in any battery-operated applications that utilise brushless 3-phase motors with single-shunt control

Aiding the development of state-of-the-art cordless home and garden power tools, two new plug-and-play boards have been introduced for controlling 3-phase brushless motors powered by up to 56V Li-ion batteries.

Based on STSPIN32 motor-control Systems-in-Package, the STEVAL-PTOOL1V1 and STEVAL-PTOOL2V1 evaluation boards fulfil key requirements of power tools including small dimensions and low standby current. Firmware is supplied for six-step motor commutation using Hall-effect rotor-position sensing, which ensures low torque ripple and optimum power efficiency.

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About STEVAL-PTOOL1V1

The STEVAL-PTOOL1V1 for equipment powered by Li-ion battery packs from two cells (7.4V) to six cells (22.2V) has a 70mm x 30mm footprint and delivers up to 15A continuous current. Standby current is less than 1µA. At the heart of the board is the STSPIN32F0B motor controller, which contains:

• STM32F0 microcontroller
• 3-phase half-bridge gate driver
• 12V and 3.3V voltage regulators
• op-amp for current sensing 
• power-stage protection features such as programmable over-current protection (OCP), cross-conduction prevention and under-voltage lockout (UVLO). 

The STEVAL-PTOOL1V1 power stage features the ST Power MOSFET N-channel 60V STripFET F7 technology.

About STEVAL-PTOOL2V1

The STEVAL-PTOOL2V1, for battery sizes from eight cells (29.6V) to 15 cells (55.5V), can deliver up to 19A continuous current. It is controlled by STSPIN32F0252 motor controller, which contains:  

• 3-phase 250V gate driver
• STM32F0 microcontroller
• comparator designed that offers very fast and flexible OCP. 

The STSPIN32F0252’s rugged design allows output pins to resist below-ground spikes down to -120V, which enhances the reliability of power tools. Featuring onboard bus voltage sensing, the STEVAL-PTOOL2V1 board measures 77mm x 54mm. The power stage features the ST Power MOSFET N-channel, 80V, STripFET F7 technology.

Both boards provide a potentiometer for speed variation, inputs for trigger and rotation-direction setting, thermal shutdown and protection against reverse biasing of power-stage outputs. They are supplied with a heatsink already mounted.

The STEVAL-PTOOL1V1 and STEVAL-PTOOL2V1 are available and can be obtained now from STMicroelectronics. The STSW-PTOOL1 firmware for STEVAL-PTOOL1V1 and STSW-PTOOL2 for STEVAL-PTOOL2V1 are downloadable free of charge from the company website.