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DRV10970: similar chip with on-chip commutation using hall sensors but with higher output PWM frequency

Hong Sun
Intellectual 300 points
Part Number: DRV10970
Other Parts Discussed in Thread: DRV10975, DRV8308

I like the DRV10970 chip as it has the commutation, current limit etc integrated within the chip such that it reduces the development time.  However as my BLDC motor (maxon EC6) has very small time constant and our final application requires to drive up to 100 such of such small motor (we will do 30 or 50  motor drivers/PCB).    I preferred to have a higher output PWM frequency in order to have a smooth driving current (smooth drive and less heat generation/more efficient).   My question is : any rule of thumb of output frequency vs. motor electrical time constant?   Is there an integrated chip similar to DRV10970 with higher output frequency (DRV10970 datasheet stated 25KHz pwm frequency for sinusoidal output)?

motor time constant = 9micro-second

Motor info is listed below:

1 Nominal voltage V      12
2 No load speed rpm      63400
3 No load current mA      29.8
4 Nominal speed rpm      46800
5 Nominal torque (max. continuous torque) mNm      0.425
6 Nominal current (max. continuous current) A      0.268
7 Stall torque mNm      1.7
8 Stall current A      0.97
9 Max. efficiency %      69
Characteristics      
10 Terminal resistance phase to phase W      12.4
11 Terminal inductance phase to phase mH      0.118
12 Torque constant mNm/A      1.75
13 Speed constant rpm/V      5460
14 Speed/torque gradient rpm/mNm      38500

thanks,

Hong

  • 0
    TI__Intellectual 2600 points

    Hong,

    Thank you for your interest in DRV10970. I feel that if the time constant of the motor is less than 100 usec you definitely want a PWM rate that is higher than 25 kHz.

    Do you require a sensored solution? If not look at DRV10975 which allows you to select either 25 kHz or 50 kHz PWM rate.

    If you do need a sensored solution you could look at DRV8308. This is a predriver but offers PWM rates up to 200 kHz.

    I hope the devices listed above will offer you a possible solution for you system.

    Thanks for the question!

    Brian

  • 0 in reply to Brian Schmidt
    Intellectual 300 points

    Brian,

    thanks for your recommendation.  Motor I have doesn't meet the pre-requisition of DRV10975 based on its data sheet.   I do prefer the sensored commutation solution so DRV8308 does work but I wish it has the driver output too.   I guess there might not have a lot of choice in integrated solution + PWM frequency requirement.   Please let me know if you do know some.  

    One more question on DRV8308, does TI have any radiation test data on the chip?

    thanks,

    Hong

  • 0 in reply to Hong Sun
    TI__Guru 54675 points
    Hong,

    Unfortunately, we do not have any EMI data for the DRV8308 that I am able to locate. Their is an EVM available for the device if you would like to evaluate it in your application.

    Regards,

    Ryan