BLDC motor controller selection

Reimer,

Thanks for posting on the MD forum!

Our newer devices like the DRV8323 can accept 6x, 3x, or 1x PWM.

In 6x you can command any type of braking/coasting or a combination since you have direct control of all 6 gate outputs. 

In 3x you only command the high side gates and the low sides are always complementary, not likely what you need.

In 1x you have a brake bit in the SPI and the INLC pin becomes a hardware brake control.

This device should fill your need as you can command it to brake/coast/reverse, it includes triple current shunt amplifiers, has internal charge pump, and drives external N-channel FETs.

We have an EVM available here if you want to try the system before building it yourself: https://www.ti.com/tool/DRV8353RS-EVM

This driver supports up to 60V so it is recommended for systems up to ~30-48V (this depends on how well you can control the vbus) to allow for headroom when the system brakes or similar that would cause the Vbus to spike up.

We also have a very similar device which supports up to 100V called the DRV8353.

Datasheets: https://www.ti.com/lit/ds/symlink/drv8323.pdf and https://www.ti.com/lit/ds/symlink/drv8353.pdf

Regards,

-Adam

Hi Adam

Thank you for the info. I have looked at the DRV8323, and it is close to what I require, but it implements slow decay mode when 1xPWM is used. I require fast decay mode for efficiency and also average current measurement (as opposed to pulse by pulse) for accurate torque control. Only way I see to implement this with the DRV8323 is if I use an external FPGA or similar to implement the trapezoidal commutation signals while the DRV8323 is used in 3xPWM mode. I would have liked to have a one-chip solution. The UC2625, which I used in the past, gives the user the choice between 2 and 4 quadrant, which is actually  the same as slow and fast decay.

It would have been nice if I could make a small change in the 6-block commutation table.

Regards

Reimer

Reimer,

Could you use 6x PWM?

Regards,

-Adam

Hi Adam

I could use 6x PWM, but in my case I think it would make no difference whether I use 6xPWM or 3xPWM.

I require the output state of the gate drive pins in the driving phases as follows:

GHA   |   GLA   |   GHB   |   GLB   |

PWM  |  !PWM |  !PWM  |   PWM  |

Therefore top and bottom gate drive pins in a phase always inverse of each other, unless both are off.

It would have been super if it was possible to change this setting in the DRV8323, then I did not need another chip for the sole purpose of handling this function.

Regards

Reimer

Reimer,

You can do the scheme mentioned above with 3x PWM, simply send PWM to INHA and !PWM to INHB.

Regards,

-Adam