Simplified development of cordless power tools

7th December 2020

Alex Lynn

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

Based on ST’s highly integrated 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.

The STEVAL-PTOOL1V1 for equipment powered by Li-ion battery packs from two cells (7.4V) to six cells (22.2V) has a 70x30mm 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 an STM32F0* microcontroller, three-phase half-bridge gate driver, 12V and 3.3V voltage regulators, an op-amp for current sensing and 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.

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 ST’s STSPIN32F0252 motor controller, which contains a 3-phase 250V gate driver, an STM32F0* microcontroller, and a comparator designed to offer 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 on-board bus voltage sensing, the STEVAL-PTOOL2V1 board measures 77x54mm. 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.

In addition to cordless tools, the boards can be used in any battery-operated applications that utilise brushless three-phase motors with single-shunt control.

The STEVAL-PTOOL1V1, priced at $41.00, and STEVAL-PTOOL2V1, $69.00, are available now. The STSW-PTOOL1 firmware for STEVAL-PTOOL1V1 and STSW-PTOOL2 for STEVAL-PTOOL2V1 can be downloaded free of charge.