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My own HW board for a 30V 25A BLDC and 40V 35A BLDC

Renaud Bobin
Intellectual 420 points
Other Parts Discussed in Thread: DRV8301, BOOSTXL-DRV8301, DRV8305, CSD18533Q5A, CSD18531Q5A

Hi, 

I have 3 different motors, and i Wish to make only one design (not necessary the same components inside) for the 3 motors :

- 15V 20A BLDC (powered from a 4S Li ion battery)
- 30V 25A BLDC (powered by a 7S Li on battery)
- 40V 35A BLDC powered by a 40V custom PSU

Is it possible to have only one design with such different motors ?

(the 15V one is not an obligation but the other 2 i hoe it is possible)

Which booster pack should i take for example ? BOOSTXL-DRV8301 / BOOSTXL-DRV8305 or something else ?

What modifications i have to make to handle 35A ?

I presume the mosfet and Shunt resistor for the current 

Thank you 

Renaud

  • 0
    TI__Mastermind 21320 points

    Hi Renaud,

    I would recommend the DRV8301 device as it supports 6-60 V operation. This will provide enough margin for the 40 V system.

    The BOOSTXL-DRV8301 only supports 6-24V so the design will need to be modified to support higher voltage and current.

    The main limitation for voltage on the BoosterPack are the bulk capacitor voltage rating. You are correct, the MOSFET and shunt resistor will need to be modified for higher current.

    The difficult may be in implementing a control algorithm for all three motors. You may need to adjust some of the sensing networks and algorithm variables for each motor PCB but the majority of the power stage can remain the same.

  • 0 in reply to Nicholas Oborny
    Intellectual 420 points

    Hi,

    Thanks for the answer.

    I don't really care if I have to have 3 different software.

    What's important is the HW design. I don't want to have 3 differents board, if i just change the resistor shunt, i'll be happy.

    So you recommand to use the DRV8301 instead of DRV8305 ? (it supports 45V so it should be good no ?)

    I prefer the DRV8305 because it has 3 current amplifier so i can save space on the board

    But i already have a BOOSTXL-DRV8301, so if i change some capacitors and the shunt resistors I may test my motors

    Does the pcb trace on the BOOSTXL-8301 can handle 30A/35A ?

  • 0 in reply to Renaud Bobin
    TI__Mastermind 21320 points

    5 V of margin for a 40 V motor system is very low. Voltage transients will occur due to regen and switching currents.

    Yes, you should be able to modify the BOOSTXL-DRV8301 to support higher voltage. Please review the schematic and BOM.

    Main items are bulk capacitors and back-emf sensing networks for voltage limitations.

    The PCB is thermally designed to handle ~10A continuous. You will need to add heat sinking or redesign the layout for more current. Heat is the limiting factor.

  • 0 in reply to Nicholas Oborny
    Intellectual 420 points

    Ok thank you

    I will design my board with a DRV8301.

    For the mosfet, is it better to have 2/3 "small" mosfet in parrallel or 1 big ?
    I was thinking of :

    • 2 CSD18533Q5A (17Ax2 at 25°C) or 2 CSD18531Q5A (19Ax2 at 25°C) in parrallel.Can we add heatsink on these packages ?
    • Rshunt of 0.001 ohm / 2W  (35A ->0.035V->1.225W) or 0.002/3W (35A -> 0.07V->2.45W)   -> amplifier gain changed to 20
    • Fb resistor 4.7k / 56k (40V -> 3.09V)

    What do you think ?

    For the 15V motor i will probably change Rshunt and Fb resistor

  • 0 in reply to Renaud Bobin
    TI__Mastermind 21320 points

    It is preferable to use 1 MOSFET when able to reduce board space and cost. Multiple is certainly an option although I wouldn't think it is required for 35 A. 

    Yes, it is possible to heat sink to the top of these packages.

    Remember that the lower the shunt value the less resolution you will receive. It is a trade off.

  • 0
    Prodigy 80 points
    Renaud,
    I'm looking for a 12V 3-phase BDCM 15A to use with my DRV8301EVM. Any suggestions on where to obtain one?
    John M.
  • 0 in reply to John Miller51
    TI__Mastermind 21320 points

    John,

    We get a lot of motors from Anaheim Automation, so that's one place. Can also check Digi-Key. I believe they have some higher current motors that would fit your description. A 200 W motor may be fairly pricey if you are just doing evaluation.

  • 0 in reply to Nicholas Oborny
    Intellectual 420 points
    Thank you
    I know for the lower the shunt value the less resolution you will receive. It is a trade off.
    But i don't have really choice for 35A i have to lower the shunt