DRV8308EVM: Use Back EMF instead of Hall Sensors?

Bryan McLaughlin

Part Number: DRV8308EVM
Other Parts Discussed in Thread: DRV8308, DRV5013, DRV8305, DRV8307

Is it possible to use Back EMF instead of Hall sensors on the DRV8308? Perhaps a biasing circuit and comparator on each phase?

The DRV8308 seems perfect for our design, but most low-cost BLDC motors do not have Hall sensors built-in. Retrofitting Hall sensors (DRV5813) is a possibility, but not ideal.

over 7 years ago

0 Bryan McLaughlin over 7 years ago

Intellectual 985 points

Correction: using DRV5013 Hall sensors.

0 Rick Duncan over 7 years ago in reply to Bryan McLaughlin

TI__Guru** 114905 points

Hi Bryan,

It may be possible, but is not recommended due to the complexity.

Prior to starting the motor, there is no Back EMF. To start the motor, the hall inputs would have to be sequenced in the proper direction.

Once running, the back emf does not transition at the same point as a hall sensor. In addition to the back emf detection, a delay would be required to mimic the hall sensor operation.

After starting and running the motor, there may be other unexpected issues that appear requiring additional circuitry.

In short, a mcu is probably required to monitor the back emf and create the hall inputs. Instead of using the mcu to make the DRV8308 operate, it is recommended to use the mcu to control a device like the DRV8305.

0 Mason Noh over 6 years ago in reply to Rick Duncan

Expert 2490 points

How about DRV8307?

Is it possible to use Back EMF instead of Hall sensors on the DRV8307?

Could you provide recomened circuit diagram??

0 Rick Duncan over 6 years ago in reply to Mason Noh

TI__Guru** 114905 points

Hi Mason,

The same constraints above apply to both the DRV8307 and DRV8308.

Motor drivers

Motor drivers forum

DRV8308EVM: Use Back EMF instead of Hall Sensors?