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DRV8825: Quiescent current

HY yang
Expert 1980 points
Part Number: DRV8825

The three pins of electric PIN24/25/26 are connected to GND. R55 and R57 are both 200m Ω. The voltage of PIN12 and PIN13 is 1V. The supply voltage, also the voltage of PIN4 and PIN11, is 24V.

Now, the problem is that after the circuit board is powered on, the DIV and STEP pins are suspended. If the EN pin is enabled, the 24V power supply has 200mA current, the motor does not rotate, and the DRV8825 heats seriously. If the motor is disconnected, the input current of 24V voltage is almost 0. Is this normal?In this case, if the STEP input signal is provided, the 24V voltage and current is about 400mA, the motor operates normally, and the DRV8825 is still severely overheated.


  • +1
    TI__Guru 55555 points

    Hello!

    When the device is first powered up, you will be in the "home" state.  I think there is a pull-up resistor on nHOME pin (looks like this is cutoff in the schematic you posted).  If there is a pull-up resistor, you can probe this pin and see that it is LOW (near 0V).  Next, check nFAULT (should also be a pull-up).  nFAULT should be HIGH indicating there is no fault state.  

    If in the HOME state and FULL STEP mode, see the following table in the datasheet.  Coil A will be at 71% of the full scale current (selected by VREF and ISENx resistors) and Coil B will also be at 71% of the full scale current.  

    As you issue STEP inputs, the current will change per the table.  Each STEP input moves one position in the table and then nHOME will go back low again once you come back to that electrical angle.  

    So, I think you are seeing normal behavior.  What is not normal is the heat.  Please reference a video and app note on this topic and how to improve your board to avoid high heat.

    https://training.ti.com/thermal-design-pcb - Video

    https://www.ti.com/lit/an/slva959b/slva959b.pdf - App Note

    Regards,

    Ryan