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DRV8316: DRVOFF Use

Daniel De Sousa
Intellectual 580 points
Part Number: DRV8316

If we are using 6xPWM, is there any need to use DRVOFF if we can turn off all FETS with the PWM interface?

  • 0
    TI__Mastermind 26046 points

    Hi Daniel,

    DRVOFF is a dedicated gate driver shutoff pin, which places all the MOSFETs in a Hi-Z state. This is equivalent to turning all of the INHx and INLx inputs low.

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Intellectual 580 points

    Thank you Aaron. Another question about the DRV8316 . . .

    In the automotive variant of the datasheet (which seems to be the most updated version of the datasheet for the 8316) shows some power calculations in section 9.2.1.1.5 to calculate the power rating of the resistor for the buck.

    This seems to be incorrect and it looks like the calculations are for a linear converter rather then a switching converter.

    Can you confirm whether this is correct / incorrect? I do not want to add a 1W resistor for no reason.

  • 0 in reply to Daniel De Sousa
    TI__Mastermind 26046 points

    Hi Daniel,

    This is the average power dissipated through the external resistor if you are using the integrated buck regulator in Resistor Mode. Resistor mode is used when the buck load current is less than 40mA and power can be saved in the device by having the power dissipated through the resistor rather than internally through the buck switching FET. 

    If you are using an inductor, the buck power dissipation inside the IC's power losses can be calculated using Table 11-1, bottom row. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Intellectual 580 points

    How does the buck know to switch into this mode?

    Would the power rating of the resistor also be related to the duty cycle considering the switching node of the buck continues to switch and thus, power is only lost in this resistor a certain percentage of time?

  • 0 in reply to Daniel De Sousa
    TI__Mastermind 26046 points

    Hi Daniel,

    It's not a defined mode, it's just adding a resistor Rbk as the buck filter component to filter the buck switching into an average output voltage. You can use Lbk or Rbk depending on the amount of load current needed to support the buck power rail. 

    We are considering average output power over continuous time. The power rating of the resistor when using Rbk should be rated for the highest power losses across the resistor using the equation from 9.2.1.1.5. 

    Thanks,
    Aaron