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Trouble with V3P3OUT on drv8825 / drv8824 - 3.3volts absent

Power_user_EX
Prodigy 50 points
Other Parts Discussed in Thread: DRV8825, DRV8824

Hi all , I am working in a design using drv8825 and drv8824. I've followed the reference design and guidelines as mentioned in the datasheet. My problem is that I m not getting 3.3 Volts output from V3P3OUT pin after powering up the board and the motor outputs (A1-2,B1-2) are also disabled. I tried using external 3.3 volts(after disconnecting V3P3OUT pin ) in which case the motor outputs were enabled but the chip would not respond to any STEP pulses - motor would stay in the same position and make noise , and after some time thermal shutdown would get triggered. I have attached my design schematic.

Where am I possibly going wrong ? (While testing - Mode(x) , decay and dir pins were pulled low)

-Regards

  • 0
    Prodigy 135 points

    In essence, you are trying to bootstrap the nSLEEP which is of course not possible. V3P3OUT will only come alive when the device is out of SLEEP mode. Hence, you cannot use V3P3OUT to take the device out of SLEEP mode.

    Applying 3.3V to nSLEEP externally is the right thing to do. What you describe then seems to be a problem with Thermal Shut Down (as you suggest). Is your Power Pad propperly soldered into a nice board area to work as heat sinking?

    Make sure your STEP pulses are at least 3 us wide. I had this problem when running my 3D printer and had to add a delay on my printer firmware to ensure the pulses were long enough. If they are too short, the device will ignore them.