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MCT8316A: Hardware interface question

Suresh leley
Prodigy 150 points
Part Number: MCT8316A
Other Parts Discussed in Thread: MCF8316A

I have few questions regarding hardware interface:

1. Is there a way to reset the MCT8316A without power cycling it? I am using MCT8316A connected to host processor on I2C port. Occasionally the MCT8316 stops responding on I2C when an incorrect or incomplete command sequence is issued. Not sure what is causing it as it happens rarely. Is there a way to recover from this without power cycling?

2. Is the external watchdog configured as latched - Hiigh Z guaranteed to always work? Looking at a catastrophic situation where the motor needs to be stopped immediately. Are there any conditions under which the MCT8316 ignores watchdog input or EXT_WD_STATUS_SET bit of ALGO_CTRL1 register? 

3. Is there a way to change motor rotation sense from I2C while permanently overriding DIR Pin? 

  • 0
    TI__Mastermind 24740 points

    Hi Suresh,

    Suresh leley said:
    1. Is there a way to reset the MCT8316A without power cycling it?

    We do not have a way to reset the MCF8316A other than power cycling the device. To try and increase the reliability of the I2C communication, we recommend using a 100 μs delay between each byte transferred over the I2C bus.

    Suresh leley said:
    2. Is the external watchdog configured as latched - Hiigh Z guaranteed to always work?

    I will need to look into this. I will get back with you by Thursday.

    Suresh leley said:
    3. Is there a way to change motor rotation sense from I2C while permanently overriding DIR Pin? 

    The motor rotation can be set to override the DIR pin an be set to clockwise rotation, OUTA-OUTB-OUTC, by setting DIR_INPUT in the PIN_CONFIG1 register to 1h. To set counter clockwise rotation, OUTA-OUTC-OUTB, set DIR_INPUT to 2h.

    Regards,

    Joshua

  • 0
    Prodigy 150 points

    Thanks Joshua, I tried setting PIN_CONFIG1.DIR_INPUT bits to 2 and it worked.

    On resetting the MCT8316A part without power cycling, I don't have any I2C communication issues at this point. This is more of a system design issue from customer perspective. The application involves multi controller-motor system, all powered by a single 24V supply. they would like to avoid power cycling individual control. I noticed the following in the datasheet:

     "If at any time the voltage on the AVDD pin falls lower than the VAVDD_UV threshold, all the integrated FETs, driver
    charge-pump and digital logic controller are disabled. Since internal circuitry in MCT8316A is powered through
    the AVDD regulator, MCT8316A goes into reset state whenever AVDD UV event occurs." 

    If there is an overload created on AVDD out pin for a short time to reset the part, would it affect Buck Out also?  If not, could this be used to reset MCT8316A?

    This won't be my preferred way to reset the part but as a last resort,   

      

  • 0 in reply to Suresh leley
    TI__Mastermind 24740 points

    Hi Suresh,

    If a VM, AVDD, or Buck under voltage condition is met then the device's logic core will be disabled and the MCT8316A will be reset. I would advise not exceeding the max current specifications for the MCT8316A's internal voltage regulators to avoid damaging the internal components.

    Joshua Horlander Cruz said:
    Is the external watchdog configured as latched - Hiigh Z guaranteed to always work?

    So long as the Watchdog fault conditions are met, the gate driver will be placed into Hi-Z mode.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 150 points

    Thanks Joshua, I am planning to use the Buck convertor to provide 5V Vcc to the host micro. If I exceed the max current specification of the AVDD output for a short period as you advised to reset the MCT8316 would it disturb the 5V provided by the buck convertor?

    Regards,

    Suresh.

  • 0 in reply to Suresh leley
    TI__Mastermind 24740 points

    Hi Suresh,

    Looks like I missed adding the word 'not' after advise, I have edited my last reply to correct this mistake. Exceeding any of the max specifications of the device could result in damage to the device or the device not operating as specified in the datasheet.

    If the device detects an AVDD undervoltage condition the MCT8316A will go into a reset state which would disturb the 5V being output by the internal buck.

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 150 points

    Ok, Thanks. We will try to convince the customer to power cycle the board or look at ways to power cycle MCT part on board. It would be nice if you can provide a pin to reset the logic part of MCT and change the I2C address to nonzero value in next version.