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Original question:

DRV8316: Hall filtering

MCT8316Z: DRVOFF Functionality

Daniel De Sousa
Intellectual 570 points
Part Number: MCT8316Z

Hello,

We are planning on not using the DRVOFF pin on the MCT8316Z but had a couple of questions first

When is the DRVOFF useful in an application?

Can this functionality be achieved via another method? Driving nSLEEP or PWM low? Over SPI?

  • 0
    TI__Mastermind 18430 points

    Hi Daniel,

    Thanks for your question!

    The purpose of DRVOFF is to put all the outputs into Hi-Z mode (meaning both high and low side MOSFETs are off for all of the phases). One important function of this pin is it can be used as an emergency stop if needed, immediately putting all the MOSFETs in Hi-Z mode. The main advantage of the DRVOFF pin is that it will put the outputs into Hi-Z mode regardless of the state of the PWM input. Another use for DRVOFF is if you wanted to coast the motor while the motor is spinning instead of actively braking the motor. One thing to keep in mind is if you coast the motor by using DRVOFF, the current in the motor will circulate through the high side body diodes of the half bridges, which can cause a pumping of the supply voltage due to the current circulating back into the battery. 

    The simplest method for putting the outputs into Hi-Z mode without using the DRVOFF pin is by writing a 1 to the COAST bit in the CONTROL_7 register. The downside of using this method over the DRVOFF method is that it is a little slower since you have to write it over a SPI command verses a single pin toggle, and if there was a condition in which SPI writes were not available or if there were any other SPI communication issues this would inhibit the ability to Hi-Z the outputs. 

    Regards,

    Anthony Lodi