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MCT8316Z: Changing direction only possible after nSLEEP is triggered

Daan Boesten
Prodigy 100 points
Part Number: MCT8316Z

We're currently testing out a MCT8316ZT on a custom PCB controlled by an STM32G4. The motor is doing well, but we've hit a snag. It seems the motor only switches direction after we enable and then disable the nSLEEP pin. Oddly enough, doing this with the BRAKE pin doesn't do the trick. We've checked the datasheet, but it doesn't tell us if this is by design or not. Do we have to 'trigger' the nSLEEP to change the motor direction?

Thank you,

Daan

  • 0
    TI__Mastermind 26746 points

    Hi Daan,

    Thank you for your question! Most of the team is out over the holidays and will be returning January 2nd, so responses may be delayed during this time. We will look into your request and provide a response hopefully the first week of January. 

    Regards,

    Anthony Lodi

  • 0
    TI__Mastermind 24660 points

    Hello Daan,

    The MCT8316Z should change the motors direction when the signal to the DIR pin is changed. The MCT8316Z should not require that the nSLEEP pin be toggled to change direction. Please do keep in mind that for the MCT8316Z, we recommend changing the motors direction with the DIR pin when the motor is stationary.

    Can you make sure that the nFAULT pin is being pulled high (2.2V to 5V) before applying the voltage on the VM pin?

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 100 points

    The same problem occurs when the motor is stationary after a brake. I'm measuring the nFAULT pin at a voltage of about 1.9V during operation, so this might be the problem. Here's the circuit of the nFAULT pin: 

  • +1 in reply to Daan Boesten
    TI__Mastermind 24660 points

    Hi Daan,

    If the nFault pin is not pulled up to >2.2V during device power up, the deice maybe entering test mode. I would measure the voltage at the nFault pin while the MCT8316Z is being powered up to make sure that the MCT8316Z is not entering test mode.

    If the nFault pin is receiving <2.2V during power up, please try and supply a voltage >2.2V to the nFault pin before and during power up to see if this corrects the devices behavior.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 100 points

    Thank you for your answer. Can the 3.3V linear regulator from the MCT8316Z be used for pulling up the nFAULT during startup? It seems that way from Figure 9-1 in the datasheet, but I'm not sure since it you mentioned that nFAULT needs to be >2.2V before applying voltage on the VM pins. 

  • 0 in reply to Daan Boesten
    TI__Mastermind 24660 points

    Hi Daan,

    The AVDD regulator can be used to pull up the nFAULT pin. Using AVDD should not make the device enter test mode.

    We recommend supplying the 3.3V to the nFAULT pullup from an external regulator before supplying power to the MCT8316Z to avoid not meeting the timing requirements and having the device enter test mode.

     Regards,

    Joshua