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MCF8316C-Q1: Voltage renge

Adam S
Expert 1110 points
Part Number: MCF8316C-Q1
Other Parts Discussed in Thread: MCF8315C, MCF8315A

Tool/software:

Hello,

I would like to ask what is the lower operating DC BUS Voltage (in other words Vlink or Inverter or just Motror DC Voltage) for the MCF8315C to operate correctly.

Datasheet says the operating voltage min is 4.5V, but in other part says it is dedicated for 12V and 24V Motors. Maybe 4.5V minimum is only for logic only?

Regards,

Adam

  • 0
    Expert 1110 points

    And also - what is the difference between part MCF8315C and MCF8315A?

  • +1 in reply to Adam S
    TI__Expert 8840 points

    Hi Adam,

    1. As shown in the Recommended Operating Conditions section, the minimum operating VM voltage is 4.5V. You can technically operate any motor at any voltage as long as it provides sufficient power to spin up the motor and doesn't exceed the motor's peak ratings. The datasheet mentions that this device is for 12V and 24V motors because those are the common industry standard operating voltages found in most applications (based on the application's supply/battery voltage or the motor's rated voltage). Some applications such as power tools use 18V batteries, so they could operate this device at 18V.

      Note: You typically want to choose motor drivers that have extra headroom in the maximum voltage vs your application operating voltage in the case of voltage feedback or transients while spinning/stopping the motor. Hence, this device is rated up to 40V abs. max, but specifically targeted up to 24V applications because we typically recommend using a motor driver that's:
      1. rated up to 1.2 × the operating voltage for well-regulated supplies and low-power motors
      2. rated up to 1.5 ~ 2 × the operating voltage for high-power motors and battery systems

    2. The difference between MCF8315C and MCF8315A is in the integrated FOC firmware algorithm version stored in the device's ROM. There were some bug fixes and minor changes to the firmware, which resulted in minor register bitfield changes (such as some bitfield name changes, bit enumeration changes, etc) But the overall device functionalities are pretty much the same.

    Regards,
    Eric C.

  • 0 in reply to Eric Chen
    Expert 1110 points

    Thank you. 

    One more question:

    Can the Buck regulator option not be used?

    I want to use two MCF8315C on Single Project where I have already enternal 3.3V Regulator.

    So can I connect output of my external 3.3V regulator to FB_BK pin of both MCF8315C and left SW_BK floating?

    Adam

  • +1 in reply to Adam S
    TI__Expert 8840 points

    Hi Adam,

    If you are looking to minimize your board space or BOM cost by removing the buck resistor/inductor and capacitor, then we recommend bypassing the internal buck regulator by connecting AVDD to the FB_BK pin.

    We don't recommend connecting your external 3.3V regulator to the FB_BK pin, since one section of the MCF device may become powered while another section is not, depending on when the external 3.3V and VM are turned on. When one section gets powered on before the other, then a power cycle would be needed to fully reset the device to ensure there is no unexpected behavior.

    Regards,
    Eric C.