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DRV8838 EN pin question

Knighty Nimp
Expert 1260 points
Other Parts Discussed in Thread: DRV8838, TPS3421

Hello

I have question about EN pin of DRV8838, I break(stop) DC motor by using push bottom switch( see diagram as attached)and control direction (forward and reverse) by MCU. When EN pin low and PH change from Hi to Low( or Low to High), how is the status of OUTA and OUTB? my target is when SW1 or SW2 on (EN  low),if PH change status, DRV8838 will be drive motor to change direction (forward or revers). Can this device work as described?

Thanks

DRV8838.pptx

NT

  • 0
    TI__Guru** 114905 points
    Hi NT,

    When EN is a logic 0 and nSLEEP is a logic 1, the outputs, both OUT1 and OUT2 are active low. Please refer to Table 2 of the datasheet for details. The PH input is a don't care.

    The motor will be driven in the direction specified by the PH pin when EN is changed to a logic 1.
  • 0 in reply to Rick Duncan
    Expert 1260 points
    Hi Rick,

    Do you have any recommend for the device which can meet our requirement?

    EN is a logic high, PH is high or low logic to control direction, we need to control motor forward and reverse with can stop at settle position in order to open or close the valve. I plan to use DC motor to replace solenoid valve. My project use 5V bush motor.

    Thank for your support

    NT
  • 0 in reply to Knighty Nimp
    TI__Guru** 114905 points
    Hi NT,

    Sorry I was not clear in the previous reply.

    The DRV8838 will meet your requirements.
  • 0 in reply to Rick Duncan
    Expert 1260 points

    Hi Rich,

    If we would like to stop the motor by 2 limit switch, the concept design is the motor turns on forward direction(PH = 0), rotates the shaft until hits a limit switch then motor stop ( water valve open) and then wait for PH signal(PH = 0) to control reverse direction,  the motor turns on until hits another limit switch( water valve close), if I understand correctly I can not use EN function because when EN is low, this device can not control the direction, in this case can I use nSLEEP pin to stop the motor and wait for PH input to control the direction of the motor?

    NT

  • 0 in reply to Knighty Nimp
    Expert 1260 points

    correct the requirement

    ==================================

    PH signal(PH = 1) to control reverse direction

    ==================================

  • 0 in reply to Knighty Nimp
    TI__Guru** 114905 points

    Hi NT,

    I am not sure the TPS3421 results in the desired operation. Reading the datasheet, it appears both pushbuttons must be pressed for many seconds before a reset pulse is issued.

    Is that what you want? If not, the TPS3421 may have to be replaced with some other circuitry.

    Sorry, I have been focusing on the DRV8838 operation.

    Can you provide the desired operation of your system in a few statements?

    Example:

    Press button, DRV8838 exits sleep mode, Motor turns in direction set by PH input until limit switch is set. DRV8838 enters sleep mode.

  • 0 in reply to Rick Duncan
    Expert 1260 points

    RIck,

    2502.DRV8838.pptxOur application have 2 switchs( see attached) when motor turn until material attach on the end of rotor reach either switch, DRV8838 will stop and then wait for PH signal( low or high) to revers the direction.

    NT

  • 0 in reply to Knighty Nimp
    TI__Guru** 114905 points
    Hi NT,

    When the switch is reached, nSLEEP is set to logic 0. What removes the logic 0 on nSLEEP so the motor can run the other direction?
  • 0 in reply to Rick Duncan
    Expert 1260 points
    Hi Rick

    We expected when PH changing from High to low( or low to high) the nSLEEP( SW) will remove automatically to high, If this can not done by this device, any solution recommended for this application?

    Thanks,
    NT
  • 0 in reply to Knighty Nimp
    TI__Guru** 114905 points
    Hi NT,

    Changing PH has no effect on nSLEEP. The switch (SW1 or SW2) is holding nSLEEP at a logic 0, which has the device disabled.

    To workaround this, you may need another switch to set nSLEEP to a logic 1 until SW1 or SW2 are disconnected. This could be a "Run" button.