DRV8844: Can DRV8844 driver piezo motor?

Hi Dahn,

danh Hoang said:

- Can we use DRV8844 to generate the required signal? Will 60V (0.2A) and 300kHz cause to stress the IC?

The main limitation here is the PWM frequency. The DRV8844 may not be capable of driving up to 300kHz while maintaining good linearity and low switching losses. Is the 60V a strict requirement? The DRV8412 can handle up to 500kHz but only 52V max operating voltage. If 52V is okay for your application, the DRV8412 will be the best device.

danh Hoang said:

- Can we use OUT1 as CW signal, OUT3 as CCW signal and OUT2 as COM. To generate CW signal, we will give two 180 degree phase difference pulses to IN1, IN2 and disable OUT3 by EN3 (similar to generate CCW signal). Can that generate a pulse that meets the requirement from -60V to 60V, 300kHz? Will the High-Z state of OUT3 be unaffected?

Correct. Swapping OUT1 and OUT3 will change current direction. OUT3 should be unaffected when in High-Z as long as OUT3 voltage remains near GND. Otherwise, there will be a small leakage from the load through OUT3 and to GND through internal paths. 

Regards,

Pablo Armet

Thanks Pablo for your answer,
1. 300kHz frequency and -60V to 60V voltage are required with our design. I have attached a picture, can you check on evb for me if the rise time, fall time, and linearity meet the requirements?

2. That's clear. OUT1, OUT2, OUT3 pins have no difference in function and electrical characteristics right? Please help us confirm this.
Thank you very much

Hi Danh,

Thank you for the information. 

danh Hoang said:

I have attached a picture, can you check on evb for me if the rise time, fall time, and linearity meet the requirements?

There is definitely some distortion at the output voltage. Most likely caused by the high frequency. Does lowering the PWM frequency resolve the issue?

danh Hoang said:

2. That's clear. OUT1, OUT2, OUT3 pins have no difference in function and electrical characteristics right? Please help us confirm this.
Thank you very much

Electrically all the OUTx pins are identical in function. 

Regards,

Pablo Armet

Hi Pablo,

It's not the loss due to the PWM frequency. The image we attached is measuring the control signal for a manufacturer's sample piezo motor operating with -50V to 50V PWM pulses.
However the motor we intend to use will also have the same PWM pulse pattern, but will be from -60 to 60V because it provides more torque.
 Can you check for me that the DRV8844 can generate the required pulse?

Regards,

Hi Danh,

I may have misunderstood your question. by -60V to 60V are you referring to flipping the polarity of the motor supply voltage (VM)? or are you referring to the voltage across the piezo motor changing from -60V to 60V?

Regards,

Pablo Armet

Hi Pablo,

I mean the voltage on the Piezo motor changes from -60V to 60V.

The VM pin is powered by 60V and the VNEG pin is connected to 0V ground. I do not design a -60V converter to power the VNEG pin because it will increase the cost of the product.

With the controls I mentioned above, can the DRV8844 generate the required voltage?

Regards,

Danh

Hi Pablo,

Grateful for your suggestions. Can you recommend me some solutions?

Regards,

Hi Dahn,

Unfortunately there are no >60V integrated H-bridge drivers in our portfolio at this time. We do have >60V grate drivers with external FETs. If you are interested in learning about our gate drivers selection, I can provide recommendations.

Regards,

Pablo Armet

Hi Pablo,

Can you provide me some solution with >60V gate driver with external FETs that meets the requirement?

Hope to get your reply soon,

Regard,