DRV8825: Equipped with your company's stepping motor driver (model: DRV8825) I am designing a printed circuit board, but the stepping motor vibrates.. If you have any advice, please let me know.

Katherine,

That is a nice report.  Couple of questions:

1)  When driving, is there an acceleration period before motor reaches the final speed?  Does vibration occur during this period or once motor reaches final speed?

2)  Have they tried using micro-stepping modes to see if that improves the vibration?

3)  I saw they swapped PCB/components.  Did they also try with different motors to see if vibration follows motor...possibly?

4)  Can the customer please share the date code of the units with vibration vs. the units with no vibration issue?  A picture of the top of the package is what I need.

Regards,

Ryan

Hi，Ryan Kehr

Thank you for your reply. I will convey your comments to the customer and look forward to your follow-up reply.

Regards,

Katherine

ライアン・ケール様

レポートを作成しました桂川電機株式会社の小泉と申します。
御世話になります。

この度はお忙しい中、ご返答頂きありがとうございます。

御連絡頂きました4項目について確認しますので
少し御時間を頂けます様お願いします。

小泉

Hi，Ryan Kehr

The person who replied to the post below is my customer, who is confirming the fourth item.

Please wait a moment, and look forward to your follow-up reply.

Thank you very much.

Regards,

Katherine

Katherine,

Any update on this?

Regards,

Ryan

Mr. Ryan Kehr

The following text is sent on behalf of customers：

TI製ステッピングモータドライバ不具合報告(20221221).pdf
I am very sorry for the late reply.

I answered your question, so please check the report.

Koizumi

Hello,

For #4, those are both valid date codes, so no issue there.  

It looks like there is just some marginality in the design and the driver is going into a HIZ state and causing the vibration.  

Can you try 1/2 step or even 1/4 step?  Increasing VREF will also increase current to maintain higher torque under micro-stepping.

Regards,

Ryan

Mr. Ryan Kehr

It is said that the driver will be in HIZ state, but are there any conditions for it to be in HIZ state?

Is it possible to vibrate if parts such as bypass capacitors are not placed correctly?

I will check the 1/2 step and 1/4 step, so please give me some time.

Koizumi

Hello,

I would do the following:

- review pcb layout, ie. connections between grounds, there are 3 different grounds: P_GND, AVSS and ground of DRV8825,

- check with an oscilloscope AVREF/BVREF against DRV8825 ground pins when the problem happens,

- check with an oscilloscope VM voltages against DRV8825 ground pins when the problem happens,

- check two phase currents at the same time and see how currents behave in both phases,

- try mixed and slow decays, and see if they change the situation,

- using slow decay I would change slowly step frequency from 0 to around 2000Hz and identify any motor resonances in that range.

Regards,

Grzegorz

Mr. Ryan Kehr

Thank you for pointing this out.

I thought that the layout of the PCB was bad, so the DRV8825
Change the board to make the layout according to the datasheet.

The three GNDs are designed as follows.

P_GND: GND to feed the sense resistor
AVSS: GND for AVREF and BVREF
ground of DRV8825: DRV8825, GND for decap of VMA and VMB

Koizumi

Hello,

Are all the GNDs connected together near the IC?  

The vias for the sense resistor connect to the PowerPad vias (under the device) on the bottom side of board.

Regards,

Ryan

Mr. Ryan Kehr

Although it is connected nearby, the bypass capacitors of VMA and VMB are mounted on the back side through vias.

The sense resistor is also mounted on the back side through vias.

I thought the layout was bad, so I will change the layout.

Koizum

Koizumi,

OK, you definitely want to minimize the inductance in the sense path.  

However, if you are changing layout, could you consider a newer device in our portfolio?  

https://www.ti.com/lit/ds/symlink/drv8434.pdf

This is an upgraded device with integrated current sense.  Layout will be much simpler and remove sense resistors.  

Regards,

Ryan

Mr. Ryan Kehr

I'm sorry.
This time, I changed it like the data sheet of DRV8825.

Future designs will also consider using the DRV8434.

koizumi

Mr. Ryan Kehr

I tried mixed damping and slow damping and the vibration disappeared.

Could you tell me the difference between the three types of attenuation modes, or how to use them?

Frequency conditions, etc.

Koizumi