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Original question:

DRV8300: How can DRV8300 supports 3xPWM?

DRV8300: DRV8300D application question

Brian Chan
Expert 7940 points

Part Number: DRV8300

Hi Team

 

I have several question as below for DRV8300D application from customer side.

 

  1. MCU PWM to DRV8300D INHA/INLA, INHB/INLB, INHC/INLC.
    1. do it need any RC circuit? if so. what is recommendation value of serial resistor and bypass capacitor?
  2. what is dead time recommendation value from 200ns to 2000ns?image.png
  3. for mode pin design. what is the benefit/weakness for design output as same polarity and what is benefit/weakness for design output as inverted polarity?

 

BRs

 

Brian

 

  • 0
    TI__Expert 8185 points

    Hi Brian,

    1. There is no RC filtering required for PWM inputs.

    2. Deadtime can be 200ns for normal safe operation. Here is a description of how Dead time affects the system.

    lower dead time – if your system is robust and you can ensure no shoot through will occur based on the input to the pre-driver. But short time can lead to shoot through typically, that is why the default is a 100ns. If your application isn’t for a BLDC motor and has the MOSFETS working separately then shoot through isn’t a problem so 50ns should be fine

     A larger dead time will reduce the chance of a shoot through condition. But high deadtime can reduce motor voltage and may not be ideal if you want high motor voltage. But it depends on your specific application. 

    3. The use of inverted polarity is so that gates can be controlled one high and one low with the same input. This is used to potentially use less MCU signals. If you wish to control each input individually with separate MCU signals, leave as same polarity.

  • 0 in reply to Joseph Ferri
    TI__Expert 7940 points

    Hi Joseph

    got it! really appreciate your detailed response Slight smile

    some more question as below.

    1. if there is no RC requirement for PWM inputs. do you think it will be a concern for EMI issue? or we can still reserve RC filter?

    2. could I share the MCU spec to you and let you comment how to set mode pin for same polarity or inverted?

    3.some SCH will add diode for discharge gate. do you think it's necessary for DRV8300D?

    4. DRV8300D spec  mention Shoot Through Prevention

    DRV8300D do also support Shoot Through Protection ( avoid high low side short ) ?

    BRs

    Brian

  • 0 in reply to Brian Chan
    TI__Expert 8185 points

    Hi Brian,

    1. There is no harm to add them, so customer can add if they want to. But usually main concern for EMI is on output side. Customer can use RC snubber and slightly higher gate resistance to limit drive current.

    2. Hi Brian, the only difference is that you would save a couple pins by operating in 3x PWM mode not 6x individual gate control. If customer does not have limited pins available on MCU then it is ok to use non-inverted mode.

    3. This is a common used diode to create seperate discharge path for the gate. I would very much recommend including a resistor here so that customer can limit the gate discharge speed to help fine-tune their sytem. They will need to experiment with gate resistor values to find best current for their MOSFETs and system.

    4. Yes the driver has shoot through protection to prevent cross conduction short event with both high and low side of same phase on.

    Thanks,

    Joseph