Hi team,
I’ve got two questions on DRV8311. Could you please take a look below, and help me understand this device more?
Q1: In my understanding, DRV8311H can be used without MCU since it has hardware interface. Is it still possible to use as sensored (meaning with current sensor) without MCU?
Q2: SPI is used for accessing the registers , right? Is there any other functions for SPI?
Best regards,
Kurumi
Hi Kurumi-san,
DRV8311H (Hardware variant) and DRV8311S (SPI variant) require external MCU if you are using 6x or 3x PWMs from the MCU to switch the integrated FETs and control the 3-phase motor. The benefit of SPI is that you can have more configurable settings over SPI and can read status registers, whereas the hardware variant allows you to configure only the GAIN, MODE, and SLEW settings through external resistors. Please see below.
The DRV8311P and DRV8311S devices allow for a special mode called 3x PWM generation mode that allows for motor control without the need for external PWMs. You can use the SPI registers to set PWM states, timer counting modes, duty cycles, and PWM periods all through SPI registers in the device. The DRV8311P (tSPI variant) uses our new tSPI technology to control multiple motors in a system using hardware address select pins (AD1:AD0) and allows for MCU synchronization using a PWM sync signal. Please see below.
You will need an external MCU for Hall-sensored based trapezoidal control to determine the position of the motor, because there is no closed loop feedback integrated into the DRV8311 devices (we have this in MCT8316Z).
Thanks,
Aaron
Hi Kurumi-san,
For Q1, you will need an MCU to generate 3 PWM or 6 PWM outputs to spin the BLDC motor in 3x PWM mode or 6x PWM mode if you are using the DRV8311H or DRV8311S. Hardware interface (DRV8311H) simply makes three of the settings (GAIN, SLEW, MODE) adjustable using a resistor, the rest of the settings are defaulted/fixed as shown below.
If you need integrated control, I would recommend looking at the MCT8316Z device, which is an integrated MOSFET driver that requires 1x PWM to spin a motor using sensored trapezoidal control with Hall sensors. You could use a 555 timer rather than an MCU to spin the motor but this requires Hall sensors.
What is the application and requirements? Does the motor need to spin at a fixed duty cycle? If you need open-loop control but require a small BOM, I would recommend a very small, cheap MSP430 MCU capable of SPI (i.e. MSP430FR2000 or MSP430FR2111) and use the DRV8311P so you can spin the motor using tSPI. Only 3 wires are needed for spinning the motor in open loop (nSCS, SCLK, SDI).
Thanks,
Aaron
