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Original question:

MCT8316Z: Any idea how to disable or modify nsleep bevahiour. Stand alone board without logic level.

MCT8315Z: Any idea how to disable or modify nsleep bevahiour. Stand alone board. Microcontroller powered by Buck Converter?

Mike Stroven
Prodigy 10 points
Part Number: MCT8315Z


Tool/software:

Hi,

This is essentially the same question asked by  a while back about the 8316Z.  I'm looking at the MCT8315Z part instead.

I'd like to build a compact stand-alone BLDC control board using the MCT8315Z having only 24VDC as my power input. Integrated buck regulator is excellent but it won't start if nsleep is low.

How can I bypass it and also clear manually nfault without a controller?  Is there a better idea than just creating a voltage divider from the Vmotor 24V input and tying it to nSLEEP?

Thanks,

-Mike

  • 0
    TI__Mastermind 26572 points

    Hi Mike,

    If your microcontroller is powered by MCT8315Z, when MCT8315Z enters sleep to wake up again we need sleep pin to go high.

    Do you need device sleep feature or always standby? 

    If we need always standby mode, then by using potential divider resistor across VM and feed to sleep pin can help to keep device in standby always. The voltage should not exceed abs max rating of the device (Refer to the datasheet)

    Thanks and Best regards

    Venkatadri S

  • 0 in reply to Venkatadri Shantaram84961
    Prodigy 10 points

    We never need standby mode.  It is baffling to me that the online example circuit which shows the microcontroller powered by the buck converter, but the sleep pin is pulled down internally.  So literally the only way to power up your micro is to pull sleep up toward the Vm supply.  It seems a bit of an oversight.  And if my microcontroller has a built-in pullup to Vdd (which many have), that pullup resistance is pulling down the sleep signal to the output of the buck converter (0V at startup).

  • 0 in reply to Mike Stroven
    TI__Mastermind 26572 points

    Hi Mike,

    Sleep pin , speed pin is having internal pull down , the typical value is 200K and max 400k ohm.

    Thanks and Best regards

    Venkatadri S

  • 0 in reply to Venkatadri Shantaram84961
    Prodigy 10 points

    But my microcontroller has a 10k pullup to it's Vdd rail, which is effectively ground at the time power (Vm is applied).  So I need a pullup that can overcome the 10K, and a zener or other clamp to keep from over-voltage on the nSLEEP pin.  Also, the direction pin seems to be completely ignored after the controller powered up.  (this should probaby be a different post, but) The part does not behave at all like the datasheet suggests.  Regardless of PWM input, the direction control does not seem to work AT ALL after powerup.

  • 0 in reply to Mike Stroven
    TI__Mastermind 26572 points

    Hi Mike,

    Can you provide some more details about the DIR pin observation? 

    We recommend DIR should be changed when motor is not spinning.

    Thanks and Best regards

    Venkatadri S