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LMD18245 3A,55V DMOS Full-Bridge Motor Driver

karunakar praveen
Prodigy 80 points
Other Parts Discussed in Thread: LMD18245, LMD18200

hi,

i am interfacing Atmega 16 to Motor driver circuit LMD18245 3A.

Whenever the PWM pulses is 0,this driver is giving 24V output.

When the PWM pulses is working then output is as per to the input given by the microcontroller,

So my question is when the PWM pulses is 0 or not given ,the output should be zero but why the output is 24Volts?

  • 0
    TI__Mastermind 21768 points

    Hi Karunakar,

    I am moving you question to the motor driver forum, in hopes that they can better help you with this question.

    Thanks,

    John

  • 0
    TI__Mastermind 22610 points

    LMD18245 3A, 55V DMOS Full-Bridge Motor Driver

    The LMD18245 does NOT have a dedicated PWM control circuitry like the LMD18200 (Pin 5 = PWM)

    How are implementing the PWM on your LMD18245?

  • 0 in reply to Donald Jones
    Prodigy 80 points

    as LMD18245 as 2 pins can be use to interface the motor.

    Direction:for clockwise or anti-clockwise

    Brake:PWM pulses output from the microcontroller to input Brake PIN.

    I have written code,

    When the BRAKE =1(means PWM pulses signals) then motor is working according to the PWM pulses.

    when Brake =0 there will be no PWM pulses,the dc motor  should not turn on.

    So how to stop the running motor,in coding ?

  • 0 in reply to karunakar praveen
    TI__Mastermind 22610 points

    I presume this is a DC PM motor running in the standard H-Bridge configuration.

    " ... When the BRAKE =1 (means PWM pulses signals) then motor is working according to the PWM pulses...."

    From the 'Pinout Descriptions' in the LMD18245 datasheet:

       "Pin 10, BRAKE: Brake logic input. Pulling the BRAKE input logic-high activates both sourcing switches of the power bridge — effectively shorting the load."

    With the LMD18245 BRAKE pin = logic high, both LMD18245 internal high-side switches will be on, so both the OUT1 and OUT 2 pins will BOTH be at (or near) the Vcc voltage. In this condition the current decay rate through the motor will depend on the characteristics of the motor.

    " ... when Brake =0 there will be no PWM pulses,the dc motor  should not turn on. ... "

    Not necessarily true. With the LMD18245 BRAKE pin = logic LOW the device is now 'active', the internal switch status (Source 1 or Source 2) will be determined by the DIRECTION pin, and the load current threshold will be set by the voltage on the DAC REF pin along with the binary setting of M1 through M4 and will activate Sink 2 or Sink 1 accordingly. The current would need to be set at a value below the motor threshold for the motor to not be activated.

    Please see the 'Switch Control Logic Truth Table' on page 3 of the LMD18245 datasheet.

    Also, please be aware that the LMD18245 logic input pins have no default state, these pins cannot be left open or in an otherwise undefined state.

     " ... So how to stop the running motor in coding ..."

    Either BRAKE pin=high (motor inputs are shorted together) (preferred), or M1 through M4 = low (motor current is set to zero).

    Back-EMF may prevent the motor from stopping as fast as you might expect, or want.

  • 0 in reply to karunakar praveen
    Prodigy 80 points

    lmd18245 IC gets heated up after 1min...............

    i am giving 24V DC and 0.25A current..

  • 0 in reply to karunakar praveen
    TI__Mastermind 21320 points

    Hi Karunakar,

    Please start a new thread with your question and more details such as a schematic, layout, application, etc.