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DRV8243H-Q1EVM: Motor drive trips at 7A even though it is rated for 12A

Rainer Binsol
Prodigy 20 points
Part Number: DRV8243H-Q1EVM
Other Parts Discussed in Thread: DRV8245-Q1, DRV8244-Q1, DRV8144-Q1

Hi,

Our application requires to run motor at 10A for 0.5 ms. We ran into a problem where the total output current from a custom board with DRV8243HQRXYRQ1 limits the output current to around 7A (@8V). Physically bypassing the drive allows to run the motor at 10A. ITRIP pin of the motor is grounded so current limiting should be disabled.

Reading the nFAULT pin the drive overheats after 3-5 seconds running at 7A, and pulls the pin low. Regardless of this the first seconds the drive seems to operate normally except the current issue.

Any suggestions to try, before switching out the drive?

  • 0
    TI__Mastermind 33865 points

    Hi,

    Thank you for your questions. Friday is national holiday in US. Will feedback to you on early of next week.

    regards

    Shinya Morita

  • 0 in reply to Shinya Morita
    TI__Mastermind 33865 points

    Hi,

    Thank you for your questions. 

    1) Over current protection.

    You mentioned 10A@0.5msec. One possibility is hitting OCP. If we capture the OUTx pin output current waveform with zoomed-in (like 10us/div) single-trigger with nFAULT pin low, peak current might be higher than OCP level.  

    2) Thermal shutdown

    FET integrated motor drive's driving current capability is impacted by thermal. 

    Here is table in Datasheet. Without PWM is less power loss than With PWM. Even without PWM, thermal shutdown could happen e.g 5.6A@1sec Ta=85C.

     

    Another remaining possibility is VMUV. VMUV may be detected due to VM voltage drop.

    regards

    Shinya Morita

  • 0 in reply to Shinya Morita
    Prodigy 20 points

    Hi!

    Thank you for the response. There was a typo in my initial text, I meant that our application requires to run motor at 10A for 0.5 seconds (not milliseconds).

    At the moment we are able to run at max 7A@8V for ~3 seconds before hitting thermal shutdown. And during that time the nFAULT pin won't be triggered. 

    I discovered the maximum amperage is more or less lineary tied to input voltage. At 5V we get max current 5A. This might be indication this has to do something with layout. I think we will try out DRV8244 with improved layout to hit 10A for 0.5 seconds.

  • +1 in reply to Rainer Binsol
    TI__Mastermind 33865 points

    Hi,

    Thank you for your update. If you are looking for 10A for 0.5sec with 20KHz PWM, DRV8244-Q1 might not be enough. (I guess you need ta=85C as max?) Even DRV8245-Q1, it is tough. 

    <<10A for 0.5sec with 20KHz PWM. 13.5V>>

    - DRV8245-Q1 is marginally OK with PWM up to 16KHz (or no PWM)- little risky.

    -DRV8244-Q1 is not OK even no PWM. up to 8.5A@0.5sec is OK.

    If you need 10A for 0.5sec with 20KHz PWM, DRV8144-Q1 x 2pcs should be solution.

    regards

    Shinya Morita

  • 0 in reply to Shinya Morita
    Prodigy 20 points

    Hi, 

    Thanks for the answer. 

    When using dual drive configuration, is it OK to interconnect both drives corresponding input/output pins?

  • 0 in reply to Rainer Binsol
    TI__Mastermind 33865 points

    Hi,

    Do you mean to use 2pcs DRV8245-Q1 and connect input/output (Works as one H-bridge IC)? DRV can not be used that way. So my response is no/not OK.

    regards

    Shinya Morita