Power Delivery in Cordless Power Tools Using DRV8329
Abstract
Cordless power tools require a small form factor and power stage to deliver up to hundreds of amps to the motor. High-performance tools, such as drills, require robust system performance powered from many types of high-quality and entry-level battery packs used across power tool platforms. To provide high torque, power tools require varying amounts of current which can deplete the battery voltage during stall conditions.
The DRV8329, a 3-phase BLDC gate driver, can help address these challenges through its hybrid bootstrap + trickle charge pump gate drive architecture to make it capable of providing at least 10V of gate-source voltage at low (~6V) supply voltages. In this application note, we will discuss how the DRV8329 meets application requirements for power tool platforms in various operating modes while also enabling system protection, consuming low quiescent current in sleep and standby modes, and maintaining a small form factor.
Figure 1-1 Various Types of Cordless Power Tools Including Drills, Saws, Cutters, Grinders, Rotary Hammers, and Impact DriversTrademarks
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1 DRV8329 Key Features
The DRV8329 is a bootstrap-based 3-phase Brushless-DC motor gate driver rated for 4.5V to 60V, and it is capable of driving 3 high-side and 3 low-side MOSFETs with up to 1-A peak source gate current and 2-A peak sink gate current. It uses a bootstrap-based architecture, which means 3 external bootstrap capacitors provide the voltage for the high-side gate driver outputs. In order to support up to 100% duty cycle, the DRV8329 includes a trickle charge pump in order to keep in the high-side MOSFETs fully on and deliver maximum motor current supported by the MOSFETs.
Furthermore, it uses a hardware interface for configuration and integrates a variety of features such as adjustable driver dead time and overcurrent threshold, an independent DRVOFF gate driver shutoff pin, current sense amplifier with low input offset and adjustable gain, a 3.3V 80-mA capable LDO, a 65-V tolerant sleep mode pin with <1uA sleep mode current, and multiple other protection features.
Available in a 36-pin, compact, 5x4mm QFN package, the DRV8329 is ideal for 2S to 10S power tool platforms with an absolute maximum rating of 65-V. This app brief showcases how the DRV8329 meets the most critical power tool requirements: performance, robustness, and scalability.