DRV8706-Q1: Question about Diodes Freewheel mode

Chase Jeong

Mastermind 7555 points

Part Number: DRV8706-Q1

Tool/software:

Dear TI experts,

My customer tests their own PCB using DRV8706SQRHBRQ1.

They have an issue about test of diode freewheel mode. Please check the waveform below.

C1: IN1 (yellow), 0V
C2: IN2 (pink), 0V
C3: GH1 (blue), 0.7V
C4: Drive out1 (green), 0.7V

I check that device goes to diode freewheel mode if IN1 and IN2 are both 0V.

And GH1 output would be also 0V, So users can spin the motor to the direction whatever they want using their hands.

But as you see GH1 is not 0V, it is about 0.7V, so FET drive out is also 0.7V. So users cannot spin the motor to the direction what they want.

Is it normal operation? or do I miss something to make GH1 output 0V in diode freewheel mode?

Please check this issue. Thanks.

Best regards,

Chase

3 months ago

0 Shinya Morita 3 months ago

TI__Mastermind 44855 points

Hi Chase,

Thank you for your question.

Yes, it is normal.

GH=low and SHx = HiZ (HS FET and LS FET are OFF).

Please refer this FAQ. SH should have weak pull up. Your customer may have some weak load on SH pin then SH pin is not purely 0V.

(3) DRV8705S-Q1EVM: why the GHx is high level when the nsleep is high level - Motor drivers forum - Motor drivers - TI E2E support forums

regards

Shinya

0 Chase Jeong 3 months ago in reply to Shinya Morita

Mastermind 7555 points

Dear Shinya,

Thank you for your support.

I understand that it is normal operation.

Then, is there any way to make GHx completely 0V while DRV8706-Q1 is working using any existing mode?

My customer just want to spin the motor in any direction using hands in certain mode.

Please check this issue. Thanks.

Best regards,

Chase

0 Shinya Morita 3 months ago in reply to Chase Jeong

TI__Mastermind 44855 points

thank You for your question. Will feedback to you an a day or two

0 Chase Jeong 3 months ago in reply to Shinya Morita

Mastermind 7555 points

Dear Shinya,

Thank you for your support.

Please let me know if there is an update.

Best regards,

Chase

0 Shinya Morita 3 months ago in reply to Chase Jeong

TI__Mastermind 44855 points

Hi Chase,

Thank you for your questions.

GH=0.7V up from SH pin should not turn ON external FET. So customer could spin motor by hand.

However if customer do not want to see some voltage on GH, nSLEEP=Low could be solution.

Could you generate new post if you have further questions? We will support you in new post.

regards

Shinya Morita