EYE on NPI - Texas Instruments DRV10974 BLDC Motor Driver

This week's EYE ON NPI is spinning up to be a good one, it's the Texas Instruments DRV10974 BLDC Motor Driver (https://www.digikey.com/en/products/detail/texas-instruments/DRV10974PWPR/9091905) a simple and powerful way to add BLDC motor control to any design, with a wide operating range and all-in-one functionality so you only need a few passives to have a full feedback-ready system for fan control. We haven't used a lot of brushless DC motors - we'll call them BLDC motors - very often here at the 'fruit but that doesn't mean they aren't an essential motor you need to know about. They are the fourth of the most common DC motors people use: steppers / linear actuators, brushed DC, and servo are the others. (Technically, servos are a type of brushed or brushless DC but they're so integrated we separate them). Brushed DC motors are great for anything that has to spin fast, and if you need more torque or lower speeds just gear them down. Brushed DC motors can be driven with a low cost H-bridges (https://en.wikipedia.org/wiki/H-bridge) such as the DRV8833 (https://www.digikey.com/short/zj9p84wr). All you need is two PWM signals to set the direction and speed - you can even add an external encoder if you want to have precise speed calculations (https://www.adafruit.com/product/4416) If you have a motor that's spinning continuously, you're better off going with a brushless motor (https://en.wikipedia.org/wiki/Brushless_DC_electric_motor): these still spin around fast like a brushed DC but give up the commutation brushes. Instead, we have to toggle one of three windings in clockwise or counter-clockwise direction to move the stator around. This isn't too bad when the motor is already running, just keep toggling them and you can pretty much guarantee the speed because you're inching the stator around. However, it's harder to start the motor because you have to slowly pulse each coil and you don't know whether the fan is keeping up or falling behind. The easiest way to handle this issue is to have hall effect sensors built into or outside the motor which can detect the permanent magnet on the rotor. But this is expensive, and annoying! So instead we can take advantage of 'back EMF', (https://en.wikipedia.org/wiki/Counter-electromotive_force) the effect on each coil from the internal permanent rotor magnet as it goes around. We can use this as a method to determine the actual speed, but the techniques for doing so are way more complex than a DC or stepper motor. Instead of just applying DC voltage, you have to perform multiple steps to begin rotation from a stop: alignment, open loop acceleration, then closed loop speed control. Which is why you want an easy-to-use chip that takes care of this logic for you, like the TI DRV10974 BLDC Motor Driver (https://www.digikey.com/short/j85mb52n)! This chip abstracts away all that complex management, and provides a direction plus speed PWM pin interface so you can use it from any microcontroller. It even has built in FETs for up to 1A continuous current draw. The DRV10974 will convert the direction / PWM pins into 3 clean sinusoids with 180 degree phases for smooth and quiet motion. It can drive delta or wye motors, with 5 to 18VDC peak to peak voltages, and from 1 to 20 ohm impedance per coil. To allow the DRV10974 to drive a wide range of motors, there are three configuration resistors that let you tweak the performance in hardware. The first resistor will set the current limit from 200mA to 1.6A. The second lets you set the lead angle, a compensation for the back EMF readings (https://www.ti.com/video/6257299020001). The third will let you adjust the acceleration profile, basically letting you optimize the startup time from when we have the sensorless open-loop startup to closed-loop running. Once you've picked the motor you want to use with the DRV, follow TI's tuning guide (https://www.ti.com/lit/ug/slou505/slou505.pdf) to select the resistors for the best performance. There's also some lock-detection built in, since not having an external encoder makes it hard to know when the motor is not running anymore. For engineers that need a brushless motor driver chip that's inexpensive, and easy to integrate, the Texas Instruments DRV10974 BLDC Motor Driver (https://www.digikey.com/short/j85mb52n) is an excellent pick with plenty of stock available at DigiKey. There's also a ready-assembled eval board, the TI DRV10974EVM (https://www.digikey.com/short/0w5qpd04) available if you want to quickly test. And of course, you can pick up a BLDC motor from DigiKey as well (https://www.digikey.com/en/products/filter/motors-ac-dc/178) Order today and your electronic items will fly faster than a rotating fan blade, from Thief River Falls to your office or home so you can start developing with the DRV10974 BLDC Motor Driver (https://www.digikey.com/short/j85mb52n) by tomorrow morning.