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DRV11873: Overcurrent Protection

na na78
Guru 16770 points
Part Number: DRV11873

Hi

I want to confirm the function of overcurrent protection and current limit.

According to the description of CS pin from datasheet, the following sentence is said.

But it is not clear for me.

"The voltage across the resistor compares with the voltage converted from the bottom MOSFETs' current.

If MOSFETs' current is high, the part goes into the overcurrent protection mode by turning off the top PWM MOSFET and keeping the bottom MOSFET on"

1.

What is the across voltage that is explained in "The voltage across the resistor compares with the voltage converted from the bottom MOSFETs' current."?

couIs it the voltage at CS pin?

2.

If the bottom MOSFET's current is higher than a current value set as Ilimit = 6600/Rcs, the device goes to overcurrent protection mode.

If overcurrent protection mode is worked once, what is happen to the device?

Is the output current limited by Ilimit value, and output current keep to flow as Ilimit?

Or it keeps low level output?

BestRegards

  • 0
    TI__Intellectual 770 points

    na na78,

       1. For across voltage information, I will get back to you.

       2. Please see below information for overcurrent

           "During overcurrent protection, DRV11873 only limits the current to the motor and it does not shut down the operation."

           "During motor start up, the overcurrent level is increased to 1.5 times the value set by RCS. If the overcurrent protection is triggered during the start up sequence, the motor will fail to start."

            This state in datasheet page 11.http://www.ti.com/lit/ds/symlink/drv11873.pdf

      Please feel free to let me know if you have more questions.

    Thanks,

    Janet

  • 0 in reply to Janet Yi
    Guru 16770 points
    Hi Janet

    Thank you.

    Regarding to 1, I'm looking forward to your reply.


    Regarding to 2, I had additional question.
    Please let me confirm following.

    "During start up sequence, the overcurrent level is increased to 1.5 times the value set by Rcs."

    That is, could it be allowed that Ilimit x 1.5 flows to motor at start up?

    For example, if Rcs is set by 3.3K, 3A can flow to motor at start up.

    Is my understanding correct?

    BestRegards
  • 0 in reply to na na78
    TI__Intellectual 770 points

    na na78,

     1. Regarding the across voltage: There is internal constant current source to flow through the resistor connect between CS pin and GND. The voltage across the resistor will compare with the voltage converted from the bottom MOSFETs current.

     2. Yes. example, if RCS set to 8.2K.base on equation current limit is 6600/8.2K ~805mA, and then 805mA*1.5 ~ 1200mA. Start up current can up to 1200mA.

    Please feel free to let me know if you have more questions. Thank you.

    Thanks again,

    Janet