DRV8714-Q1: fast decay question

Sherry Liang

Part Number: DRV8714-Q1

Dear team,

There is one app note in DRV8714-Q1 page. In this note, it introduces different decay mode. There is one synchronous decay which will turn on the opposing FET switches. My question is how do we make sure the motor won't rotate in reverse direction when turning on the opposing FET switches?

Thanks & Best Regards,

Sherry

over 2 years ago

0 Shinya Morita over 2 years ago

TI__Mastermind 44315 points

Hi Sherry,

Let me review your question and feedback to you within 24hous.

regards

Shinya Morita

0 Shinya Morita over 2 years ago in reply to Shinya Morita

TI__Mastermind 44315 points

Hi Sherry,

DRV8714-Q1 does not monitor the motor current to avoid reverse rotation. External circuit need to control DRV to avoid reverse rotation.

DRV8714-Q1 has current sense amp(SPx, SNx, SOx). Customer may be able to re-use this to check motor current.

regards

Shinya Morita

0 Sherry Liang over 2 years ago in reply to Shinya Morita

TI__Genius 10255 points

Hi Shinya,

Thanks for your reply!

In my understanding, the current direction on the motor can't be changed immediately, so even if a reverse voltage is applied, the motor won't rotate in reverse until the current decays down to zero, right?

Thanks & Best Regards,

Sherry

+1 Shinya Morita over 2 years ago in reply to Sherry Liang

TI__Mastermind 44315 points

Hi Sherry,

Yes, your understanding is correct.

regards

Shinya Morita

+1 Brian Dang over 2 years ago

Genius 5040 points

Sherry Liang said:
My question is how do we make sure the motor won't rotate in reverse direction when turning on the opposing FET switches?

Hi Sherry,

I assume you use a driver to control the FETs, and so I assume also that the driver input is PWM controlled. So during fast decay, the current flow by the opposite FETs turned on will be controlled by the driver internal circuit if you chose to use this fast decay mode, as the driver will turn off BH at the right moment. Of course if you use your own microprocessor to control the FETs then you have to know when to turn off BH before the motor running in reverse.

Brian

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DRV8714-Q1: fast decay question